Removal of dyes from water using Citrullus lanatus seed powder in continuous and discontinuous systems.

The objective of this study is to develop a low-cost biosorbent using residual seeds of the Citrullus lanatus fruit for the removal of cationic dyes. Physicochemical parameters such as pH, adsorbent mass, contact time, and temperature were evaluated for their effects on dye removal. The biosorbent is composed of lignin and cellulose, exhibiting a highly heterogeneous surface with randomly distributed cavities and bulges. The adsorption of both dyes was most effective at natural pH with a dosage of 0.8 g L-1. Equilibrium was reached within 120 min, regardless of concentration, indicating rapid kinetics. The Elovich model and pseudo-second-order kinetics were observed for crystal violet and basic fuchsin dye, respectively. The Langmuir model fitted well with the equilibrium data of both dyes. However, the increased temperature had a negative impact on dye adsorption. The biosorbent also demonstrated satisfactory performance (R = 43%) against a synthetic mixture of dyes and inorganic salts, with a small mass transfer zone. The adsorption capacities for crystal violet and basic fuchsin dye were 48.13 mg g-1 and 44.26 mg g-1, respectively. Thermodynamic studies confirmed an exothermic nature of adsorption. Overall, this low-cost biosorbent showed potential for the removal of dyes from aqueous solutions.

In this work, a novel biosorbent was developed using residual Citrullus lanatus fruit seeds that can efficiently remove cationic dyes from aqueous solutions. The biosorbent's composition includes lignin and cellulose, and its surface structure is highly heterogeneous, consisting of randomly distributed cavities and bulges. The biosorbent demonstrated a rapid and efficient adsorption capacity for both crystal violet and basic fuchsin, regardless of dye concentration. Moreover, the biosorbent was successfully employed in the treatment of a synthetic mixture containing several dyes and inorganic salts. Finally, the application of the biosorbent in continuous adsorption showed a low zone of mass transfer and high breakthrough time, indicating it to be an excellent material for fixed-bed operation. Overall, this study provides a low-cost and efficient alternative for the removal of dyes from aqueous solutions, with promising practical applications.

"Long COVID" and Its Impact on The Environment: Emerging Concerns and Perspectives.

The COVID-19 pandemic has caused unprecedented global health and economic crises. The emergence of long COVID-19 has raised concerns about the interplay between SARS-CoV-2 infections, climate change, and the environment. In this context, a concise analysis of the potential long-term effects of the COVID-19 epidemic along with the awareness aboutenvironmental issues are realized. While COVID-19 effects in the short-term have reduced environmental air pollutants and pressures, CO2 emissions are projected to increase as the economy recovers and growth rates return to pre-COVID-19 levels. This review discusses the systematic effects of both the short-term and long-term effects of the pandemic on the clean energy revolution and environmental issues. This article also discusses opportunities to achieve long-term environmental benefits and emphasizes the importance of future policies in promoting global environmental sustainability. Future directions for growth and recovery are presented to cope with long COVID-19 epidemic along with the critical findings focussing on various aspects: waste management, air quality improvement.

Enhancing Methylene Blue Dye Removal using pyrolyzed Mytella falcata Shells: Characterization, Kinetics, Isotherm, and Regeneration through Photolysis and Peroxidation.

The potential of pyrolyzed Mytella falcata shells as an adsorbent for removing methylene blue dye molecules from aqueous solutions was investigated. The study found that the adsorbent produced at 600 °C of pyrolysis temperature, with an adsorbent mass of 0.5 g, particle diameter of 0.297-0.149 mm, and pH 12.0, demonstrated the highest dye molecule removal efficiency of 82.41%. The material's porosity was observed through scanning electron microscopy, which is favorable for adsorption, while Fourier-transform infrared spectroscopy and X-Ray diffraction analysis analyses confirmed the presence of calcium carbonate in the crystalline phases. The pseudo-second order model was found to be the best fit for the data, suggesting that the adsorption mechanism involves two steps: external diffusion and diffusion via the solid pores. The Redlich-Peterson isotherm model better represented the equilibrium data, and the methylene blue adsorption was found to be spontaneous, favorable, and endothermic. The hydrogen peroxide with UV oxidation was found to be the most efficient method of regeneration, with a regeneration percentage of 63% achieved using 600 mmol.L-1 of oxidizing agents. The results suggest that pyrolyzed Mytella falcata shells could serve as an ecologically viable adsorbent alternative, reducing the amount of waste produced in the local environment and at the same time removing pollutants from the water. The material's adsorption capacity remained almost constant in the first adsorption-oxidation cycles, indicating its potential for repeated use.

The Synthesis and Evaluation of Porous Carbon Material from Corozo Fruit (Bactris guineensis) for Efficient Propranolol Hydrochloride Adsorption.

This study explores the potential of the corozo fruit (Bactris guineensis) palm tree in the Colombian Caribbean as a source for porous carbon material. Its specific surface area, pore volume, and average pore size were obtained using N2 adsorption/desorption isotherms. The images of the precursor and adsorbent surface were obtained using scanning electron microscopy (SEM). Fourier transform infrared (FTIR) spectra were obtained to detect the main functional groups present and an X-ray diffraction analysis (XRD) was performed in order to analyze the structural organization of the materials. By carbonizing the fruit stone with zinc chloride, a porous carbon material was achieved with a substantial specific surface area (1125 m2 g⁻1) and pore volume (3.241 × 10-1 cm3 g⁻1). The material was tested for its adsorption capabilities of the drug propranolol. The optimal adsorption occurred under basic conditions and at a dosage of 0.7 g L⁻1. The Langmuir homogeneous surface model effectively described the equilibrium data and, as the temperature increased, the adsorption capacity improved, reaching a maximum of 134.7 mg g⁻1 at 328.15 K. The model constant was favorable to the temperature increase, increasing from 1.556 × 10-1 to 2.299 × 10-1 L mg-1. Thermodynamically, the adsorption of propranolol was found to be spontaneous and benefited from higher temperatures, indicating an endothermic nature (12.39 kJ mol⁻1). The negative ΔG0 values decreased from -26.28 to -29.99 kJ mol-1, with the more negative value occurring at 328 K. The adsorbent material exhibited rapid kinetics, with equilibrium times ranging from 30 to 120 min, depending on the initial concentration. The kinetics data were well-represented by the general order and linear driving force models. The rate constant of the general order model diminished from 1.124 × 10-3 to 9.458 × 10-14 with an increasing concentration. In summary, the leftover stone from the Bactris guineensis plant can be utilized to develop activated carbon, particularly when activated using zinc chloride. This material shows promise for efficiently adsorbing propranolol and potentially other emerging pollutants.

Hotspots and Trends of Layered Double Hydroxide-based Adsorbents for Polluted Water Treatment: Insights from Bibliometric Analysis.

The use of layered double hydroxides (LDHs) as adsorbent for water treatment has been gaining relevance in recent years. In this context, this work aimed to map, through a bibliometric study, the extent of research that deals with the theme. The scientific database used was the Web of Science, and the chronology of the search consideredthe period from 1997 to 2022. The bibliometix R-package and VOSviewer software were used in this study. The searches retrieved a total of 663 documents, from 69 countries, distributed among all continents, which China (328), India (51) and Japan (40) were the most productive countries. Important journals in the environmental area and with high impact factor, such as Chemical Engineering Journal (44), Applied Clay Science (38), Journal of Hazardous Materials (35) and Chemosphere (27) most published in the area. The network of keywords used by the authors indicates that the publications retrieved deal mainly with aspects related to the efficiency of (LDHs) in the removal of different pollutants, the composition, the synthesis route and the association with other materials and/or techniques. The result of this study constitutes an important tool for directing future research on the subject.

Adsorption of the First-Line Covid Treatment Analgesic onto Activated Carbon from Residual Pods of Erythrina Speciosa.

In this study, the residual pods of the forest species Erythrina speciosa were carbonized with ZnCl2 to obtain porous activated carbon and investigated for the adsorptive removal of the drug paracetamol (PCM) from water. The PCM adsorption onto activated carbon is favored at acidic solution pH. The isothermal studies confirmed that increasing the temperature from 298 to 328 K decreased the adsorption capacity from 65 mg g-1 to 50.4 mg g-1 (C0 = 175 mg L-1). The Freundlich model showed a better fit of the equilibrium isotherms. Thermodynamic studies confirmed the exothermic nature (ΔH0 = -39.1066 kJ mol-1). Kinetic data indicates that the external mass transfer occurs in the first minutes followed by the surface diffusion, considering that the linear driving force model described the experimental data. The application of the material in the treatment of a simulated effluent with natural conditions was promising, presenting a removal of 76.45%. Therefore, it can be concluded that the application of residual pods of the forest species Erythrina speciosa carbonized with ZnCl2 is highly efficient in the removal of the drug paracetamol and also in mixtures containing other pharmaceutical substances.

Layered Double Hydroxides as Rising-Star Adsorbents for Water Purification: A Brief Discussion.

Within the frame of this article, briefly but comprehensively, we present the existing knowledge, perspectives, and challenges for the utilization of Layered Double Hydroxides (LDHs) as adsorbents against a plethora of pollutants in aquatic matrixes. The use of LDHs as adsorbents was established by considering their significant physicochemical features, including their textural, structural, morphological, and chemical composition, as well as their method of synthesis, followed by their advantages and disadvantages as remediation media. The utilization of LDHs towards the adsorptive removal of dyes, metals, oxyanions, and emerging pollutants is critically reviewed, while all the reported kinds of interactions that gather the removal are collectively presented. Finally, future perspectives on the topic are discussed. It is expected that this discussion will encourage researchers in the area to seek new ideas for the design, development, and applications of novel LDHs-based nanomaterials as selective adsorbents, and hence to further explore the potential of their utilization also for analytic approaches to detect and monitor various pollutants.

Ouricuri (Syagrus coronata) fiber: a novel biosorbent to remove methylene blue from aqueous solutions.

In this work, the potential of ouricuri (Syagrus coronata) fiber as a novel biosorbent to remove methylene blue (MB) from aqueous solutions was investigated. The fiber was prepared and characterized according to the fundamental features for adsorption. A 23 experimental design was used to evaluate the effects of adsorbent dosage (M), fiber diameter (D) and agitation (A) on the adsorption capacity. In the more adequate conditions, kinetic and equilibrium studies were performed. The experimental design results showed that M = 10 g L-1), D = 0.595 mm and A = 200 rpm were the more adequate conditions for MB adsorption. Based on the kinetic study, it was found that the adsorption process was fast, being the equilibrium was attained at about 5 min, with 90% of color removal. The isotherm was properly represented by the Sips model, and the maximum adsorption capacity was 31.7 mg g-1. In brief, it was demonstrated that ouricuri fiber is an alternative biosorbent to remove MB from aqueous media, taking into account the process efficiency and economic viewpoint.

Comparison between Brazilian agro-wastes and activated carbon as adsorbents to remove Ni(II) from aqueous solutions.

This research was performed to find an alternative, low-cost, competitive, locally available and efficient adsorbent to treat nickel (Ni) containing effluents. For this purpose, several Brazilian agro-wastes like sugarcane bagasse (SCB), passion fruit wastes (PFW), orange peel (OP) and pineapple peel (PP) were compared with an activated carbon (AC). The adsorbents were characterized. Effects of fundamental factors affecting the adsorption were investigated using batch tests. Kinetic and equilibrium studies were performed using conventional models. It was verified that the adsorption was favored at pH of 6.0 for all agro-wastes, being dependent of the Ni speciation, point of zero charge and surface area of the adsorbents. The Ni removal percentage was in the following order: SCB > OP > AC > PFW > PP. From the kinetic viewpoint, the Elovich model was appropriate to fit the Ni adsorption onto SCB, while for the other adsorbents, the pseudo-first-order model was the most suitable. For all adsorbents, the Langmuir model was the more adequate to represent the equilibrium data, being the maximum adsorption capacities of 64.1 mg g(-1), 60.7 mg g(-1), 63.1 mg g(-1), 48.1 mg g(-1) and 64.3 mg g(-1) for SCB, PFW, OP, PP and AC, respectively. These results indicated that mainly SCB and OP can be used as alternative adsorbents to treat Ni containing effluents.

Production of MgAl/layered double hydroxide microspheres and investigation of the volumetric heat transfer coefficient in spray drying.

Layered Double Hydroxides (LDH) are synthetic materials nanostructured in two dimensions that present positively charged layers with interspersed anions for charge and structure balancing. Being recognized as a promising material for various applications, a complete exploration of its possible attractive properties and its synthesis process is essential. However, drying, a necessary step in the process, is still little studied. This work aimed to produce MgAl-CO3/LDH microspheres and calculate the volumetric heat coefficient in spray drying, evaluating the drying air inlet temperature and the concentration of the feed paste in the dryer. LDH synthesis was carried out using the coprecipitation method, maintaining a 2:1 Mg/Al ratio. The infrared spectra presented the bands characteristic of the hydrotalcite-type material. Through XRD, it was possible to observe that the variation in drying air temperature and feed paste concentration produced LDHs with structural differences. The results obtained for the basal spacing ranged from 7.685 to 7.705 Å. Scanning electron microscopy images confirm the production of LDH microspheres, showing variation in the size of the agglomerates with changes in the feed paste concentration. The volumetric heat transfer coefficient values ranged from 4.31 to 5.36 W m-3 K-1, with only the air inlet temperature significantly influencing the process under the conditions studied.

A critical and comprehensive review of the current status of 17ß-estradiol hormone remediation through adsorption technology.

Even at low concentrations, steroid hormones pose a significant threat to ecosystem health and are classified as micropollutants. Among these, 17ß-estradiol (molecular formula: C18H24O2; pKa = 10.46; Log Kow = 4.01; solubility in water = 3.90 mg L-1 at 27 °C; molecular weight: 272.4 g mol-1) is extensively studied as an endocrine disruptor due to its release through natural pathways and widespread use in conventional medicine. 17ß-estradiol (E2) is emitted by various sources, such as animal and human excretions, hospital and veterinary clinic effluents, and treatment plants. In aquatic biota, it can cause issues ranging from the feminization of males to inhibiting plant growth. This review aims to identify technologies for remediating E2 in water, revealing that materials like graphene oxides, nanocomposites, and carbonaceous materials are commonly used for adsorption. The pH of the medium, especially in acidic to neutral conditions, affects efficiency, and ambient temperature (298 K) supports the process. The Langmuir and Freundlich models aptly describe isothermal studies, with interactions being of a low-energy, physical nature. Adsorption faces limitations when other ions coexist in the solution. Hybrid treatments exhibit high removal efficiency. To mitigate global E2 pollution, establishing national and international standards with detailed guidelines for advanced treatment systems is crucial. Despite significant advancements in optimizing technologies by the scientific community, there remains a considerable gap in their societal application, primarily due to economic and sustainable factors. Therefore, further studies are necessary, including conducting batch experiments with these adsorbents for large-scale treatment along with economic analyses of the production process.

Environmental remediation of the norfloxacin in water by adsorption: Advances, current status and prospects.

Antibiotics are considered as the new generation water pollutants as these disturb endocrine systems if water contaminated with antibiotics is consumed. Among many antibiotics norfloxacin is present in various natural water bodies globally. This antibiotic is considered an emerging pollutant due to its low degradation in aquatic animals. Besides, it has many side effects on human vital organs. Therefore, the present article discusses the recent advances in the removal of norfloxacin by adsorption. This article describes the presence of norfloxacin in natural water, consumption, toxicity, various adsorbents for norfloxacin removal, optimization factors for norfloxacin removal, kinetics, thermodynamics, modeling, adsorption mechanism and regeneration of the adsorbents. Adsorption takes place in a monolayer following the Langmuir model. The Pseudo-second order model represents the kinetic data. The adsorption capacity ranged from 0.924 to 1282 mg g-1. In this sense, the parameters such as the NFX concentration added to the adsorbent textural properties exerted a great influence. Besides, the fixed bed-based removal at a large scale is also included. In addition to this, the simulation studies were also discussed to describe the adsorption mechanism. Finally, the research challenges and future perspectives have also been highlighted. This article will be highly useful for academicians, researchers, industry persons, and government authorities for designing future advanced experiments.

Synthesis of layered double hydroxides: Investigating the impact of stirring conditions and reactor design parameters.

The synthesis by coprecipitation of Layered Double Hydroxides (LDHs) is governed by the stages of nucleation and crystal growth associated with the efficiency of the mixing and dispersion process of the reagents. Mixing efficiency is related to process variables, such as agitation speed, type of impeller and baffles presence, among others. In this context, this work proposes an analysis of these variables in a batch reactor, using a 23 factorial design employing the factors: acceleration speed (200 and 1000 rpm), mixing time (2 and 18 h) and presence or absence of baffles. The results were evaluated quantitatively (amount of LDH produced, time and amount of base for the formation of LDHs to begin) and qualitatively (mixing aspects, sedimentation ad grinding). The significant factors affecting the amount of LDH produced (51.94-80.81 g) were agitation speed and aging time. These factors were also correlated with the structural characteristics of the materials produced, such as crystallinity, crystallite size (70.99-174.79 nm), surface area (69.81-97.62 m2/g), pore volume (0.28-0.59 cm3/g), and pore diameter (11.40-34.66 nm). LDHs produced at higher agitation rates (1000 rpm) and longer aging times (18 h) yielded higher quantities of materials (80.81 g) with improved structural characteristics. The study highlights the importance of systematically exploring the synergistic effect between process variables, emphasizing the research potential in this area.

Adsorption of leather dye onto activated carbon prepared from bottle gourd: equilibrium, kinetic and mechanism studies.

Activated carbon prepared from bottle gourd has been used as adsorbent for removal of leather dye (Direct Black 38) from aqueous solution. The activated carbon obtained showed a mesoporous texture, with surface area of 556.16 m(2) g(-1), and a surface free of organic functional groups. The initial dye concentration, contact time and pH significantly influenced the adsorption capacity. In the acid region (pH 2.5) the adsorption of dye was more favorable. The adsorption equilibrium was attained after 60 min. Equilibrium data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The equilibrium data were best described by the Langmuir isotherm, with maximum adsorption capacity of 94.9 mg g(-1). Adsorption kinetic data were fitted using the pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The adsorption kinetic was best described by the second-order kinetic equation. The adsorption process was controlled by both external mass transfer and intraparticle diffusion. Activated carbon prepared from bottle gourd was shown to be a promising material for adsorption of Direct Black 38 from aqueous solution.

Use of papaya seeds as a biosorbent of methylene blue from aqueous solution.

In this study papaya seeds were used to remove methylene blue dye from aqueous solution. Papaya seeds were characterized as possessing a macro/mesoporous texture and large pore size. Studies were carried out in batches to evaluate the effect of contact time and pH (2-12) on the removal of dye. It was observed that the adsorption of dye was better in the basic region (pH 12). The equilibrium data were analyzed using Langmuir, Freundlich, Dubinin-Raduschkevich, Tempkin, Jovanovich, Redlich-Peterson, Sips, Toth and Radke-Prausnitz isotherms. The equilibrium data were best described by the Langmuir isotherm with a maximum adsorption capacity of 637.29 mg g(-1). Adsorption kinetic data were fitted using the pseudo-first-order and pseudo-second-order model. The adsorption kinetic is very fast and was best described by the pseudo-second-order model.

Conversion of foliar residues of Sansevieria trifasciata into adsorbents: dye adsorption in continuous and discontinuous systems.

The study analyzed the potential of leaf powder prepared from the residual leaves of the species Sansevieria trifasciata, as a potential adsorbent for methylene blue (MB) removal. The equilibrium was reached fast for almost all concentrations after 60 min, obtaining the maximum capacity of 139.98 mg g-1 for 200 mg L-1. The increase in temperature disfavored the dye adsorption, with the maximum adsorption capacity of 225.8 mg g-1, observed for 298 K. The thermodynamic parameters confirmed that the adsorption process is spontaneous and exothermic. A direct sloping curve was established for the fixed bed, with breakthrough time (tb), column stoichiometric capacities (qeq), and the mass transfer zone lengths (Zm) were 1430, 1130, and 525 min; 60.48, 187.01, and 322.65 mg g-1; and 8.81, 11.28, and 10.71 cm, for 100, 200, and 500 mg L-1, respectively. Furthermore, in a mixture of several dyes, the adsorbent obtained the removal of 51% of the color.

A comprehensive review on nanocatalysts and nanobiocatalysts for biodiesel production in Indonesia, Malaysia, Brazil and USA.

Biodiesel is an alternative to fossil-derived diesel with similar properties and several environmental benefits. Biodiesel production using conventional catalysts such as homogeneous, heterogeneous, or enzymatic catalysts faces a problem regarding catalysts deactivation after repeated reaction cycles. Heterogeneous nanocatalysts and nanobiocatalysts (enzymes) have shown better advantages due to higher activity, recyclability, larger surface area, and improved active sites. Despite a large number of studies on this subject, there are still challenges regarding its stability, recyclability, and scale-up processes for biodiesel production. Therefore, the purpose of this study is to review current modifications and role of nanocatalysts and nanobiocatalysts and also to observe effect of various parameters on biodiesel production. Nanocatalysts and nanobiocatalysts demonstrate long-term stability due to strong Brønsted-Lewis acidity, larger active spots and better accessibility leading to enhancethe biodiesel production. Incorporation of metal supporting positively contributes to shorten the reaction time and enhance the longer reusability. Furthermore, proper operating parameters play a vital role to optimize the biodiesel productivity in the commercial scale process due to higher conversion, yield and selectivity with the lower process cost. This article also analyses the relationship between different types of feedstocks towards the quality and quantity of biodiesel production. Crude palm oil is convinced as the most prospective and promising feedstock due to massive production, low cost, and easily available. It also evaluates key factors and technologies for biodiesel production in Indonesia, Malaysia, Brazil, and the USA as the biggest biodiesel production supply.

The production of activated biochar using Calophyllum inophyllum waste biomass and use as an adsorbent for removal of diuron from the water in batch and fixed bed column.

The Calophyllum inophyllum species annually produces a large volume of cylindrical fruits, which accumulate on the soil because they do not have nutritional value. This study sought to enable the use of this biomass by producing activated biochar with zinc chloride as an activating agent for further application as an adsorbent in batch and fixed bed columns. Different methodologies were used to characterize the precursor and the pyrolyzed material. Morphological changes were observed with the emergence of new spaces. The carbonaceous material had a surface area of 468 m2 g-1, Dp = 2.7 nm, and VT = 3.155 × 10-1 cm3 g-1. Scientific and isothermal studies of the adsorption of the diuron were conducted at the natural pH of the solution and adsorbent dosage of 0.75 g L-1. The kinetic curves showed a good fit to the Avrami fractional order model, with equilibrium reached after 150 min, regardless of the diuron concentration. The Liu heterogeneous surface model well represented the isothermal curves. By raising the temperature, adsorption was encouraged, and at 318 K, the Liu Qmax was reached at 250.1 mg g-1. Based on the Liu equilibrium constant, the nonlinear van't Hoff equation was employed, and the ΔG° were < 0 from 298 to 328 K; the process was exothermic nature (ΔH0 = -46.40 kJ mol-1). Finally, the carbonaceous adsorbent showed good removal performance (63.45%) compared to a mixture containing different herbicides used to control weeds. The stoichiometric column capacity (qeq) was 13.30 and 16.61 mg g-1 for concentrations of 100 and 200 mg L-1, respectively. The length of the mass transfer zone was 5.326 cm (100 mg L-1) and 4.946 cm (200 mg L-1). This makes employing the leftover fruits of the Calophyllum inophyllum species as biomass for creating highly porous adsorbents a very effective and promising option.

Sewage sludge-derived biochar for the adsorptive removal of wastewater pollutants: A critical review.

The production of biochar from sewage sludge pyrolysis is a promising approach to transform the waste resultant from wastewater treatment plants (WWTPs) to a potential adsorbent. The current review provides an up-to-date review regarding important aspects of sewage sludge pyrolysis, highlighting the process that results major solid fraction (biochar), as high-value product. Further, the physio-chemical characteristics of sewage-sludge derived biochar such as the elemental composition, specific surface area, pore size and volume, the functional groups, surface morphology and heavy metal content are discussed. Recent progress on adsorption of metals, emerging pollutants, dyes, nutrients and oil are discussed and the results are examined. The sewage sludge-derived biochar is a promising material that can make significant contributions on pollutants removal from water by adsorption and additional benefit of the management of huge volume of sewage. Considering all these aspects, this field of research still needs more attention from the researchers in the direction of the technological features and sustainability aspects.