Potential of Capparis decidua plant and eggshell composite adsorbent for effective removal of anionic dyes from aqueous medium.

The presence of hazardous dyes in wastewater poses significant threats to both ecosystems and the natural environment. Conventional methods for treating dye-contaminated water have several limitations, including high costs and complex operational processes. This study investigated a sustainable bio-sorbent composite derived from the Capparis decidua plant and eggshells, and evaluated its effectiveness in removing anionic dyes namely tartrazine (E-102), methyl orange (MO), and their mixed system. The research examines the influence of initial concentration, contact time, pH, adsorbent dosage, and temperature on the adsorption properties of anionic dyes. Optimal removal of tartrazine (E-102), methyl orange (MO), and their mixed system was achieved at a pH of 3. The equilibrium was achieved at 80 min for MO and mixed systems, and 100 min for E-102. The adsorption process showed an exothermic nature, indicating reduced capacity with increasing temperature, consistent with heat release during adsorption. Positive entropy values indicated increased disorder at the solid-liquid interface, attributed to molecular rearrangements and interactions between dye molecules and the adsorbent. Isotherm analysis using Langmuir, Freundlich, Temkin, and Redlich-Peterson models revealed that the Langmuir model best fit the experimental data. The maximum adsorption capacities of 50.97 mg/g, 52.24 mg/g, and 56.23 mg/g were achieved for E-102, MO, and the mixed system under optimized conditions, respectively. The pseudo-second-order kinetic model demonstrated the best fit, indicating that adsorption occurs through physical and chemical interactions such as electrostatic attraction, pore filling, and hydrogen bonding. Hence, the developed bio-sorbent could be a sustainable and cost-effective solution for the treatment of anionic dyes from industrial effluents.

Investigation of the efficacy of Alhagi maurorum plant powder for Janus Green B dye removal from wastewater.

The growth of industrial activities, has led to a significant increase in the influx of color pollutants into the environment. Phytoremediation can play a crucial role in enhancing wastewater quality. Accordingly, this study sought to evaluate the effectiveness of Alhagi maurorum plant powder in removing Janus Green B (JGB) dye from aqueous solutions. The adsorbent's properties were characterized through Fourier-transform infrared spectroscopy. The study examined various parameters, including initial dye concentration (20-110 mg/L), adsorbent dosage (0.002-0.02 g), solution pH (2-10), and contact time (5-50 min). The experiments revealed that the maximum dye removal efficiency, 99.51%, was achieved under optimal conditions: pH 7, a contact time of 20 min, an adsorbent dosage of 0.01 g, and an initial dye concentration of 90 mg/L. The adsorption of JGB onto the adsorbent followed the Langmuir isotherm model, with a maximum adsorption capacity of 90.909 mg/g. The kinetic results supported a pseudo-second-order model for the adsorption process, with an R2 value of 0.9999. The calculated Gibbs free energy changes (ΔG°) at temperatures of 288, 298, 308, 318, and 328 K were found to be -5354.28, -5993.61, -6439.66, -7026.51, and -7932.05 kJ/mol, respectively, indicating the spontaneity of the adsorption process.

This study investigated the capabilities of Alhagi maurorum species for removing Janus Green B in wastewater, because A. maurorum is considered a weed in fields and can be found in abundance in desert areas. It is a low-cost and eco-friendly adsorbent.

Biosorption of a common micropollutant (methylene blue) from a water environment by chemically activated biomass of a widely available plant species (Pyracantha coccinea M. J. Roemer).

Recently, to protect the health of aquatic life and, indirectly, all living things, biomass-based substances have been increasingly applied as biosorbent materials to remove micropollutant agents from an aquatic environment. However, these studies are under development, and the search for more successful materials continues. Here, the biosorption of a common micropollutant, methylene blue, from an aquatic environment was investigated using the chemically activated biomass of a widely available plant species, Pyracantha coccinea M. J. Roemer. The biosorption efficiency of the biosorbent material was improved by optimizing the experimental conditions, including the contact time, micropollutant load, pH, and biosorbent material amount, and the highest performance was observed at t = 360 mins, C0 = 15 mg L-1, pH = 8 and m = 10 mg. The pseudo-second-order kinetics model and Freundlich isotherm model were in good agreement with the experimentally obtained results. The thermodynamic study suggested that the micropollutant biosorption was a favorable, spontaneous, and physical process. The micropollutant-biosorbent interaction mechanism was presented using SEM and FTIR studies. The maximum Langmuir biosorption capacity of the biosorbent was determined to be 156.674 mg g-1. The activation operation more than doubled the biosorption potential of the biosorbent material. Thus, the present study showed that the chemically activated plant biomass-based material could be a promising biosorbent for the effective removal of the micropollutant from water environment.

The biosorption of a common micropollutant, methylene blue, from a water environment was studied using chemically activated biomass of Pyracantha coccinea M. J. Roemer. The activation operation more than doubled the biosorption potential of the biosorbent material. It exhibited higher micropollutant biosorption performance compared to most other biosorbents. These results indicated that the chemically activated biomaterial could be a very effective biosorbent for the micropollutant biosorption from an aqueous medium.

Interaction between Haematococcus pluvialis microalgae and lead nitrate: lead adsorption from water.

Our study aims to investigate the response of the unicellular alga, Haematococcus pluvialis, to the toxicity of lead and propose a low-cost, highly efficient biological adsorbent for the purification of wastewater and lead-contaminated water. The first part examines the effects of lead toxicity on certain physiological indicators of this alga. In the second part, the potential of this alga in lead removal and its adsorption capacity was assessed. The alga was cultivated in a BG11 medium and treated with lead nitrate concentrations of 10, 50, and 200 mg/L during its exponential growth. The results showed that with an increase in lead concentration up to 200 mg/L, the growth rate, chlorophyll a, chlorophyll b, carotenoid and total protein content decreased, while malondialdehyde (MDA) content increased. The astaxanthin content slightly increased at the 10 mg/L but decreased at the 200 mg/L treatment. Maximum lead adsorption was observed at 98.69% under optimal conditions, including a pH of 6, an adsorbent dose of 1 g/L, a lead concentration of 25 mg/L, a temperature of 25 °C, and an exposure time of 120 min. The results of this study demonstrate that Haematococcus pluvialis has the potential for effective lead removal from aquatic environments.

While the influence of heavy metals on certain algae species has been explored, research on the impact of lead on Haematococcus pluvialis­a microalga of significant interest for astaxanthin production­remains uncharted territory. Therefore, understanding the impact of this heavy metal and the alga's metal absorption capabilities has profound implications for biotechnology and bioremediation applications. This study promotes H. pluvialis as an economically viable lead absorbent suitable for both industrial and domestic purposes.

Unlocking Agronutrient Resources: Sorption Strategies for sugar-energy industry waste.

Vinasse and ash from sugarcane bagasse (SCB) are key byproducts in the sugar-energy industry. Vinasse is nutrient-rich but environmentally challenging, while sugarcane bagasse ash (SCBA) offers excellent adsorbent for treating effluents. This work aims to assess the effectiveness of SCBA in removing nitrogen (N) and potassium (K) nutrients from Vinasse. Simulated standard solutions of K2SO4 and (NH4)2HPO4 were used to mimic the nutrient concentrations in Vinasse and optimize experimental parameters such as adsorbent mass and contact time. Kinetic and isotherm models were also applied to elucidate the underlying adsorption mechanisms. Structural, morphological, and thermal analyses revealed the micro-mesoporous and heterogeneous nature of SCBA, primarily composed of SiO2 (quartz and cristobalite). The sorption assessment indicated the ideal conditions involved lower SCBA masses (2.5 g) and 6 h of contact time for the simulated standard solutions. The replicated conditions for Vinasse (at an adjusted sorption time of 24 h) demonstrated nutrient sorption and pH correction of the Vinasse, attributed to the alkaline nature of SCBA. Analysis of the sorption kinetic models for K+ and NH4+ revealed that SCBA interacts diffusively with the environment, not necessarily controlled by adsorption on active sites, indicating non-uniform characteristics. The sorption isotherms for K+ and NH4+ showed the non-linearized Freundlich model was the most suitable, indicating the adsorption sites with varying energy levels and a multilayer sorption process. In conclusion, we successfully demonstrated the sorption of nutrients from Vinasse by SCBA, enhancing the value of these residues and mitigating their environmental impact when used in agricultural applications.

Deep removal of phosphate from electroplating wastewater using novel Fe-MOF loaded chitosan hydrogel beads.

Since the electroplating industry is springing up, effective control of phosphate has attracted global concerns. In this study, a novel biosorbent (MIL-88@CS-HDG) was synthesized by loading a kind of Fe-based metal organic framework called MIL-88 into chitosan hydrogel beads and applied in deep treatment of phosphate removal in electroplating wastewater. The adsorption capacities of H2PO4- on MIL-88@CS-HDG could reach 1.1 mmol/g (corresponding to 34.1 mg P/g and 106.7 mg H2PO4-/g), which was 2.65% higher than that on single MOF powders and chitosan hydrogel beads. The H2PO4- adsorption was well described by the Freundlich isotherm model. Over 90% H2PO4- could be adsorbed at contact time of 3 h. It could keep high adsorption capacity in the pH range from 2 to 7, which had a wider pH range of application compared with pure MIL-88. Only NO3- and SO42- limited the adsorption with the reduction rate of 11.42% and 23.23%, proving it tolerated most common co-existing ions. More than 92% of phosphorus could be recovered using NaOH and NaNO3. Electrostatic attraction between Fe core and phosphorus in MIL-88@CS-HDG and ion exchange played the dominant role. The recovered MIL-88@CS-HDG remained stable and applicable in the treatment process of real electroplating wastewater even after six adsorption-regeneration cycles. Based on the removal properties and superb regenerability, MIL-88@CS-HDG is potentially applicable to practical production.

A Sustainable Solution for the Adsorption of C.I. Direct Black 80, an Azoic Textile Dye with Plant Stems: Zygophyllum gaetulum in an Aqueous Solution.

The presence of pollutants in water sources, particularly dyes coming by way of the textile industry, represents a major challenge with far-reaching environmental consequences, including increased scarcity. This phenomenon endangers the health of living organisms and the natural system. Numerous biosorbents have been utilized for the removal of dyes from the textile industry. The aim of this study was to optimize discarded Zygophyllum gaetulum stems as constituting an untreated natural biosorbent for the efficient removal of C.I. Direct Black 80, an azo textile dye, from an aqueous solution, thus offering an ecological and low-cost alternative while recovering the waste for reuse. The biosorbent was subjected to a series of characterization analyses: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), and infrared spectroscopy (IR) were employed to characterize the biosorbent. Additionally, the moisture and ash content of the plant stem were also examined. The absorption phenomenon was studied for several different parameters including the effect of the absorption time (0 to 360 min), the sorbent mass (3 to 40 g/L), the pH of the solution (3 to 11), the dye concentration (5 to 300 mg/L), and the pH of the zero-charge point (2-12). Thermodynamic studies and desorption studies were also carried out. The results showed that an increase in plant mass from 3 to 40 g/L resulted in a notable enhancement in dye adsorption rates, with an observed rise from 63.96% to 97.08%. The pH at the zero-charge point (pHpzc) was determined to be 7.12. The percentage of dye removal was found to be highest for pH values ≤ 7, with a subsequent decline in removal efficiency as the pH increased. Following an initial increase in the amount of adsorbed dye, equilibrium was reached within 2 h of contact. The kinetic parameters of adsorption were investigated using the pseudo-first-order, pseudo-second-order and Elovich models. The results indicated that the pseudo-first-order kinetic model was the most appropriate for the plant adsorbent. The isotherm parameters were determined using the Langmuir, Frendlich, Temkin, and Dubinin-Radushkevich models. The experimental data were more satisfactory and better fitted using the Langmuir model for the adsorption of dye on the plant. This study demonstrated that Zygophyllum gaetulum stems could be employed as an effective adsorbent for the removal of our organic dye from an aqueous solution.

Techno-economic feasibility and life cycle assessment analysis for a developed novel biosorbent-based arsenic bio-filter system.

Significant aquifers around the world is contaminated by arsenic (As), that is regarded as a serious inorganic pollution. In this study, a biosorbent-based bio-filter column has been developed using two different plant biomasses (Colocasia esculenta stems and Artocarpus heterophyllus seeds) to remove total As from the aqueous system. Due to its natural origin, affordability, adaptability, removal effectiveness, and possibility for integration with existing systems, the biosorbent-based bio-filter column presents an alluring and promising method. It offers a practical and eco-friendly way to lessen the damaging impacts of heavy metal contamination on ecosystems and public health. In this system, As (III) is oxidized to As (V) using chlorine as an oxidant, after this post-oxidized As-contaminated water is passed through the bio-filter column to receive As-free water (or below World Health Organization permissible limit for As in drinking water). Optimization of inlet flow rate, interference of co-existing anions and cations, and life cycle of the column were studied. The maximum removal percent of As was identified to be 500 µg L-1 of initial concentration at a flow rate of 1.5 L h-1. Furthermore, the specifications of the biosorbent material was studied using elemental analysis and Zeta potential. The particle size distribution, morphological structures, and chemical composition before and after binding with As were studied using dynamic light scattering (DLS), scanning electron microscope-energy dispersive X-Ray spectroscopy (SEM-EDX), and fourier's transform infrared spectroscopy (FTIR) analysis, respectively. SuperPro 10 software was used to analyze the techno-economic viability of the complete unit and determine its ideal demand and potential. Life cycle assessment was studied to interpret the environmental impacts associated alongside the process system. Therefore, this bio-filtration system could have a potential application in rural, urban, and industrial sectors.

Sustainable approach for the expulsion of metaldehyde: risk, interactions, and mitigation: a review.

All pests can be eliminated with the help of pesticides, which can be either natural or synthetic. Because of the excessive use of pesticides, it is harmful to both ecology and people's health. Pesticides are categorised according to several criteria: their chemical composition, method of action, effects, timing of use, source of manufacture, and formulations. Many aquatic animals, birds, and critters live in danger owing to hazardous pesticides. Metaldehyde is available in various forms and causes significant impact even when small amounts are ingested. Metaldehyde can harm wildlife, including dogs, cats, and birds. This review discusses pesticides, their types and potential environmental issues, and metaldehyde's long-term effects. In addition, it examines ways to eliminate metaldehyde from the aquatic ecosystem before concluding by anticipating how pesticides may affect society. The metal-organic framework and other biosorbents have been appropriately synthesized and subsequently represent the amazing removal of pesticides from effluent as an enhanced adsorbent, such as magnetic nano adsorbents. A revision of the risk assessment for metaldehyde residuals in aqueous sources is also attempted.

Investigation of Eucalyptus camaldulensis and Tamarix aphylla species' capacities for methylene blue removal in wastewater and heavy metal remediation in soil.

In the contemporary landscape, the reuse of wastewater holds paramount significance. Concurrently, wastewater carries an array of pollutants encompassing chemical dyes and heavy metals. This study delves into the potential of Tamarix aphylla (TA) and Eucalyptus camaldulensis (EC) species for mitigating heavy metals in soil and eliminating methylene blue dye (MB) from wastewater. The research begins with assessing the dye adsorption process, considering pivotal factors such as initial pH, adsorbent dosage, initial dye concentration, and contact time. Outcomes reveal EC's superiority in dye removal compared to TA. As a bioremediation agent, EC exhibits a 90.46% removal efficacy for MB within 15 min, with pH 7.0 as the operative condition. Equilibrium analysis employs Temkin (T), Freundlich (F), and Langmuir (L) isotherms, revealing an excellent fit with the L isotherm model. The study delves further by probing surface adsorption kinetics through pseudo-first-order (PFO) and pseudo-second-order (PSO) models. Furthermore, to discern the divergent impacts of EC and TA on soil heavy metal reduction, soil samples were collected from three distinct zones: an untouched control area, alongside areas where EC and TA were cultivated at the Yazd wastewater site in Iran. Heavy metal levels in the soil were meticulously assessed through rigorous measurement and statistical scrutiny. The findings spotlight TA-cultivated soil as having the highest levels across all examined factors. Ultimately, EC emerges as the superior contender, proficiently excelling in both MB eliminations from wastewater and heavy metal amelioration in the soil, positioning it as the preferred phytoremediation agent.

Evaluating cottonwood seeds as a low-cost biosorbent for crystal violet removal from aqueous matrics.

In this study, cottonwood seeds (CWS) were introduced as a novel, green, and low-cost biosorbents for the removal of crystal violet (CV) dye from aqueous solutions. To illustrate the characteristics of CWS, surface morphology, Fourier-transform infrared spectroscopy, field emission scanning electron microscopes, and energy dispersive X-ray spectroscopy techniques were employed. Important adsorption variables (i.e., equilibrium time, solution pH, CWS amount, CV concentration, and temperature) were systematically studied. Maximum CV dye adsorption was observed at pH 10 using 20 mg of the adsorbent. Different adsorption isotherms were investigated, and the results were more accurately consistent with the Langmuir model (R2 = 0.992). The maximum capacity of adsorption was 153.85 mg g-1 at 60 min. The kinetic data were examined by different models and a pseudo-second-order model supplied the best correlation between experimental data. Investigated thermodynamic parameters at different temperatures illustrated that the CV adsorption procedure was spontaneous and endothermic with an increase in entropy. The percentage removal and the relative standard deviations for the real sample analysis were in the range of 89-98% and 4.9-9.5%, respectively. High adsorption capacity and low equilibrium time demonstrated that CWS is an impressive biosorbent for dye pollutants uptakes from aqueous solutions and real industrial wastewater samples.

A novel, green, available, and low-cost cottonwood seeds were introduced for the removal of crystal violet from aqueous media. In terms of adsorption capacity and contact time, cottonwood seeds show excellent performance compared to the other low-cost biosorbents previously reported for the adsorption of the organic dye from wastewater. The use of cottonwood seeds to remove environmental pollutants has not been introduced yet.

Adsorption of Brilliant Green Dye onto a Mercerized Biosorbent: Kinetic, Thermodynamic, and Molecular Docking Studies.

This study reports the valorization of pistachio shell agricultural waste, aiming to develop an eco-friendly and cost-effective biosorbent for cationic brilliant green (BG) dye adsorption from aqueous media. Pistachio shells were mercerized in an alkaline environment, resulting in the treated adsorbent (PSNaOH). The morphological and structural features of the adsorbent were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, and polarized light microscopy. The pseudo-first-order (PFO) kinetic model best described the adsorption kinetics of the BG cationic dye onto PSNaOH biosorbents. In turn, the equilibrium data were best fitted to the Sips isotherm model. The maximum adsorption capacity decreased with temperature (from 52.42 mg/g at 300 K to 46.42 mg/g at 330 K). The isotherm parameters indicated improved affinity between the biosorbent surface and BG molecules at lower temperatures (300 K). The thermodynamic parameters estimated on the basis of the two approaches indicated a spontaneous (ΔG < 0) and exothermic (ΔH < 0) adsorption process. The design of experiments (DoE) and the response surface methodology (RSM) were employed to establish optimal conditions (sorbent dose (SD) = 4.0 g/L and initial concentration (C0) = 10.1 mg/L), yielding removal efficiency of 98.78%. Molecular docking simulations were performed to disclose the intermolecular interactions between the BG dye and lignocellulose-based adsorbent.

Biosorption of toxic metal ions (Cr+6, Cd2+) and nutrients (PO43-) from aqueous solution by diatom biomass.

This paper evaluates diatom biomass as a biosorbent for removing Cr+6, Cd2+, and PO43- ions from water. The diatom was characterized by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Scanning Electron Microscopy (SEM-EDS) for its crystallinity, functional groups, and morphology. A batch sorption study was conducted to evaluate the parameters influencing Cr+6, Cd2+, and PO43- ions adsorption, and the mechanisms were explored. The FTIR spectra revealed Si-O, O-H, N-H, and C-O as the main functional groups present on the surface of the adsorbent. The SEM showed a rough and irregular-shaped morphology, while the EDS indicated that the diatom biomass is an aluminosilicate material. The rate-limiting steps for Cr+6 and Cd2+ were pseudo-first order, and pseudo-second order sorption favored PO43- based on their R2 values. Moreover, the dominant adsorption model that best described the equilibrium data was the Freundlich isotherm. The maximum adsorption capacities obtained for Cr+6 was 5.66 (mg/g), and Cd2+ was 5.27 (mg/g) at 313 K while PO43- was 19.13 (mg/g) at 298 K. The thermodynamic data revealed that the reaction was endothermic for Cd2+ and exothermic for Cr+6 and PO43-, respectively. Diatom biomass was observed to be a promising bio-sorbent for removing Cr6+, Cd2+ and PO42- from wastewater.

Biosorption of methylene blue by residue from Lentinus crinitus mushroom cultivation.

Conventional textile effluent treatments cannot remove methylene blue, a mutagenic azo dye, and an endocrine disruptor, that remains in the drinking water after conventional water treatment. However, the spent substrate from Lentinus crinitus mushroom cultivation, a waste, could be an attractive alternative to remove persistent azo dyes in water. The objective of this study was to assess the methylene blue biosorption by spent substrate from L. crinitus mushroom cultivation. The spent substrate obtained after mushroom cultivation had been characterized by the point of zero charge, functional groups, thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. Moreover, the spent substrate biosorption capacity was determined in function of pH, time, and temperature. The spent substrate had a point of zero charge value of 4.3 and biosorbed 99% of methylene blue in pH from 3 to 9, with the highest biosorption in the kinetic assay of 15.92 mg g- 1, and in the isothermal assay of 120.31 mg g- 1. Biosorption reached equilibrium at 40 min after mixing and best fitted the pseudo-second-order model. Freundlich model best fitted the isothermal parameters and each 100 g spent substrate biosorbed 12 g dye in an aqueous solution. The spent substrate of L. crinitus cultivation is an effective biosorbent of methylene blue and an alternative to removing this dye from water, adding value to the mushroom production chain, and supporting the circular economy.

Equilibrium, kinetics, and thermodynamics study on the biosorption of reactive levofloxacin antibiotic on Pithophora macroalgae in aqueous solution.

Since untreated wastewater from hospitals and residential areas is being discharged directly into surface waterways, pharmaceutical contaminants have been shown to be higher in many countries. Therefore, the development of novel and effective techniques to extract antibiotic substances from wastewater is of utmost importance. The present work aims at the use of green Pithophora macroalgae to remove levofloxacin antibiotic from an aqueous solution through biosorption. Biosorption is an economical and eco-friendly method for treating wastewater. The macroalgae were dried, grounded, and used as biosorbent to remove the levofloxacin (LVX) antibiotics from the aqueous solution. The influence of operating conditions such as initial antibiotic concentration, biosorbent dosage, agitation speed, pH, and temperature was studied. The biosorbent was characterized by FTIR, SEM, and point zero charge. The experimental data were evaluated using Langmuir and Freundlich isotherms. The experimental data best fit the Freundlich isotherm model (R2 = 0.969), while the kinetic model for the experiment follows the pseudo-second-order (R2 = 0.998) with a maximum biosorption capacity of 17.8 mg/g. Maximized removal of LVX occurs at favorable conditions of 298 K temperature, 150 mg/L initial concentration of antibiotic, 0.5 g sorbent dose, and 6.5 pH. The calculated thermodynamic parameters reveal that the biosorption of LVX antibiotics occurs by an endothermic process. This study deduces that Pithophora macroalgae biomass proved to be an effective biosorbent for biosorption of LVX antibiotics and may be a novel alternative method for antibiotics removal from aqueous solutions.

Potential application of spent mushroom compost (SMC) biochar as low-cost filtration media in heavy metal removal from abandoned mining water: a review.

Overpopulation and rapid development have put an increasing burden on the environment, leading to various water crisis. Importing water from abandoned mines as an alternative raw water source could be the next answer to alleviate water scarcity problems globally. However, due to its high heavy metals content, there is a need to find an economical and effective method to remove heavy metals before reusing it as potable water source. Biochar, a low-cost and carbon-rich biosorbent, has received increasing attention on its application as a remediating agent to remove heavy metals from water. Previous studies have revealed the potential properties of biochar as a heavy metal removal agent including high cation exchange capacity, high surface area, active surface functional groups, as well as efficient adsorption. Apparently, the most important factor influencing the sorption mechanism is the type of feedstock materials. Spent mushroom compost (SMC), a waste product from mushroom cultivation, has been found as an excellent biosorbent. SMC has received global attention as it is low cost and eco-friendly. It also has been proved as an efficient heavy metals remover from water. Nevertheless, its application as biochar is still scarce. Therefore, this review focuses on the potential of transforming SMC into modified biochar to remove heavy metals, especially from abandoned mining water. The present review emphasizes the current trends in adsorption methods for heavy metal removal from water, assembles data from previous studies on the feedstock of biosorbents to biochars, and discusses the potentials of SMC as a biochar for water treatment.

Biosorption of heavy metals from aqueous solutions using activated sludge, Aeromasss hydrophyla, and Branhamella spp based on modeling with GEOCHEM.

This work tests the technical applicability of sewage sludge and isolated dead cells of Aeromasss hydrophyla and Branhamella spp for the elimination of inorganic pollutants such as Zn(II), Pb(II), Cd(II), and/or Cu(II) using synthetic wastewater with their initial concentrations of 100 mg/L, respectively. The sludge samples were collected from local sewage treatment plants. The effects of dose and pH on heavy metals removal were evaluated in batch studies and their removal performances were compared to those of previous studies. Both the Freundlich and the Langmuir models were plotted to study their biosorption using activated sludge and the bacteria. Isotherm data, resulting from the batch studies, were compared to the modeling results of Geochem. It was evident that the activated sludge could achieve 99% of Zn(II), Cd(II), Cu(II) and Pb(II) removal with 100 mg/L of concentration at pH 6.0 and 3 g/L of dose. Under the same conditions, 97% of Cd(II), Cu(II) and/or Pb(II) was removed by Aeromasss hydrophyla and Branhamella spp, as indicated by their adsorption capacities (activated sludge: 99.07 mg Pb2+/g; dewatered sludge: 57.15 mg Pb2+/g; digested sludge: 83.58 mg Pb2+/g; 24.47 mg Cd2+/g; Aeromasss hydrophylla: 71.91 mg Pb2+/g; Branhamella spp: 37.52 mg Cu2+/g). Of the four heavy metals studied, Pb(II) had the highest metal adsorption capacity for all adsorbents studied (Pb2+>Cu2+> Cd2+>Zn2+). The modeling results of the Geochem fitted well with the isotherm data of the batch studies at varying concentrations from 20 to 100 mg/L. The thermodynamic constant at pH 4 were comparable to those obtained from previous works. This indicates a reliable prediction over varying metal concentrations and pHs of the batch studies. In spite of the promising results, the treated effluents still could not meet the required effluent limits set by local legislation. Therefore, it is necessary to subsequently treat the samples using biological processes such as activated sludge.

Sorption of arsenic by composts and biochars derived from the organic fraction of municipal solid wastes: Kinetic, isotherm and oral bioaccessibility study.

The historic contamination of water and soils by arsenic (As) is an extremely alarming environmental and public health issue worldwide. This study investigated the relationship between As sorption and physicochemical properties of composts and biochars derived from the organic fraction of municipal solid wastes (OFMSW) towards the development of promising sorbents with value-added solid wastes management solutions. The sorbents were characterized and their effectiveness on the As sorption was tested. Several isothermal and kinetic sorption models were used for the prediction of sorption. Composts did not show promising sorption capacities, and in some cases, the As immobilization was practically null. In contrast, biochars achieved higher sorption performance, and the experimental data fitted well on Dubinin-Rabushkevich and Langmuir models, with higher R2 values. The maximum sorption capacities of BC700 estimated by such models were 6.495 and 170.252 mg g-1, respectively, whereas those of BC500 estimated by D-R and Langmuir models were only 0.066 and 0.070 mg g-1, respectively. In sorption kinetics, As was retained onto biochars at a faster first stage, reaching equilibrium after approximately 1 h and 2 h for initial concentrations of 10 and 100 mg L-1. The pseudo-second-order, Ritchie's second-order, Ritchie's, and Elovich models more adequately described the sorption kinetics of As onto biochars with high R2 values. Overall, the complexation and precipitation were predominant mechanisms for As sorption by OFMSW-derived biochars. Furthermore, the mathematical models indicated contributions arise from physisorption and external and internal diffusion mechanisms. Although BC700 can immobilize large As amounts, the gastric phase of the oral bioaccessibility test revealed more than 80% of the sorbed As could be released under conditions similar to a human stomach (pH~1.2). Such conclusions have given important insights about the refining of effective and eco-friendly remediation technologies for the management and rehabilitation of As-contaminated soil and water, particularly in developing countries.

Biosorption and adsorption isotherm of chromium (VI) ions in aqueous solution using soil bacteria Bacillus amyloliquefaciens.

This study looked at the development of effective biosorbents to recover the most toxic elements from industrial water. B. amyloliquefaciens was isolated from marine soils showing extreme resistance to Chromium (Cr(VI)) ions. During the 60 min of contact time, 79.90% Cr(VI) was adsorbed from the aqueous solution. The impact of important factors such as biomass concentration, pH of the medium, and initial metal ions concentration on biosorption rate was also examined. The desorption study indicated that 1 M HCl (91.24%) was superior to 0.5 M HCl (74.81%), 1 M NaOH (64.96%), and distilled water (3.66%). Based on the Langmuir model, the maximum adsorption capacity of the bio-absorbent was determined to be 48.44 mg/g. The absorption mechanism was identified as monolayer, and 1/n from the Freundlich model falls within 1, thus indicating favorable adsorption. Based on the findings of the present study, the soil bacterium B. amyloliquefaciens was found to be the best alternative and could be used to develop strategies for managing existing environmental pollution through biosorption.

Adsorption of pollutants in wastewater via biosorbents, nanoparticles and magnetic biosorbents: A review.

Adsorption has gained much attention as one of the efficient approaches to remediate the contaminants in wastewater. Herein, this critical review focuses on the preparation, modification, application and regeneration of the biosorbents, nanoparticles and magnetic biosorbents for the wastewater treatment in recent 5 years (2017-2021). Among these materials, the development of magnetic biosorbents is attractive owing to their variable active sites, high specific surface area, easy separation and low cost. To improve the adsorption performance of biosorbents, the chemical activations such as acid, alkali and salt activations of biosorbents are discussed. In general, the oxidation reaction in acid, alkali and salt activations increases the porosity of biosorbents. The surface characteristics, surface chemistry of the biosorbents and magnetic biosorbents such as electrostatic interaction, π-π interaction and hydrogen bonding are highlighted. Ionic compounds are separated through ion exchange, surface charge and electrostatic interactions while the organic pollutants are removed via hydrophobicity, π-π interactions and hydrogen bonding. The effect of solution pH, adsorbent dosage, initial concentration of pollutants, adsorption duration and temperature on the adsorption capacity, and removal efficiency are discussed. Generally, an increase in adsorbent dosage resulted in a decrease in adsorption capacity due to the excessive active sites. On the other hand, a higher initial concentration or an increase in contact time of adsorbent increased the driving force, subsequently enhancing the adsorption capacity. Finally, this review will be concluded with a summary, challenges and future outlook of magnetic biosorbents. It is anticipated that this review will provide insights into engineering advanced and suitable materials to achieve cost-effective and scalable adsorbents for practical and sustainable environmental remediation.