Removal of Rhodamine-B dye from Aqueous Solutions Using Alkaline-Modified Activated Carbon from Cocoa Pod Husk.

Rhodamine-B (RhB) dye in wastewater poses health and environmental risks due to respiratory and eye infections, neurotoxicity, and carcinogenicity, necessitating proper disposal for risk mitigation. This study investigates RhB removal from water using NaOH-modified activated carbon derived from cocoa pod husk (CPHAC). Employing a face-centered central composite design, operational variables were optimized to achieve maximum RhB dye removal efficiency. The study reveals a removal efficiency of 98.87 ± 0.84% under optimized conditions: adsorbent dose of 1.34 g, contact time of 71.59 min, and an initial RhB concentration of 6.61 ppm. The Freundlich isotherm model demonstrated a good fit, suggesting that RhB removal is governed by heterogeneity and multilayer adsorption. Kinetic experiments revealed that adsorption follows a pseudo-second-order model, indicating likely irreversible adsorption with dye molecules forming chemical bonds on CPHAC's surface. Overall, this study demonstrates the effectiveness of CPHAC as an efficient adsorbent for RhB removal from water.

Adsorption simulation of 2,4-D pesticide on novel zinc-based 2-amino-4-(1H-1,2,4-triazole-4-yl)benzoic acid coordination complexes using machine learning approach.

The capacity of zinc-based 2-amino-4-(1H-1,2,4-triazole-4-yl)benzoic acid coordination complex (Zn(NH2-TBA)2) and modified Zn(NH-TBA)2COMe complex for removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions was investigated through adsorption modeling and artificial intelligence tools. Analyzing the adsorption characteristics of pesticides helps in studying the groundwater pollution by pesticides in agriculture area.In this study, Zn(NH2-TBA)2 was synthesized using Schiff base and its surface was modified using acetic anhydride group and their physical characteristics were identified using proton NMR, FTIR, and XRD. NMR results showed maximum modification yield obtained was 65% after 5 days. The porous structure and surface area monitored using nitrogen isotherm and BET surface area analysis presented relatively less surface area and porosity after modification. Adsorption modelling indicated that Toth model with a maximum adsorption capacity of 150.8 mg/g and 100.7 mg/g represents the homogenous adsorption systems which satisfy both low- and high-end boundary of adsorbate concentration in all settings according to the optimum point, while the kinetics and rate of 2,4-D adsorption follow the pseudo-first-order kinetic model in all situations. Artificial neural network (ANN), support vector regression, and particle swarm optimized least squares-support vector regression (PSO-LSSVR) were used for the optimization and modelling of adsorbent mass, adsorbate concentration, contact time, and temperature to develop predictive equations for the simulation of the adsorption efficiency of 2,4-D pesticide. The obtained results exhibited the better performance of ANN and PSO-LSSVR for prediction of adsorption results. The mean square error values of ANN (0.001, 0.012) and PSO-LSSVR (0.121, 0.105) were obtained for Zn(NH2-TBA)2 and Zn(NH-TBA)2COMe, respectively, while their respective coefficient of determination (R2) obtained were 0.999 and 0.988 for ANN and 0.980 and 0.825 for PSO-LSSVR. The study specified that machine learning predictive behavior performed better for Zn(NH2-TBA)2 compared to Zn(NH-TBA)2COMe that is also supported by theoretical kinetics and isotherm models. The research concludes that artificial intelligence models are the most efficient tools for studying the predictive behavior of adsorption data.

Competitive heavy metal adsorption on pinecone shells: Mathematical modelling of fixed-bed column and surface interaction insights.

Pinecone shells are assessed as a cost-effective biosorbent for the removal of metal ions Pb(II), Cu(II), Cd(II), Ni(II), and Cr(VI) in a fixed-bed column. Influent concentration, bed height, and flowrate are studied to improve efficiency. The breakthrough data is well fitted by the Sips adsorption model, suggesting a surface complexation mechanism, with maximum adsorption capacities of 11.1 mg/g for Cu(II) and 66 mg/g for Pb(II). In multimetal solutions, the uptake sequence at breakthrough and saturation is Pb(II) > Cu(II) > Cd(II). Characterization via FTIR and XRD reveals carboxyl and hydroxyl functional groups interacting with metal ions. Ca(II) does not compete with Pb(II), Cu(II), and Cd(II) adsorption, highlighting the ability of pinecone to adsorb heavy metals via surface complexation. Its application in the treatment of industrial effluents containing Cu(II), Ni(II), and Cr(VI) is explored. The study investigates bed media regeneration via eluting adsorbed metal ions with hydrochloric acid solutions. The potential of pinecone shells as an efficient biosorbent for removing toxic metal ions from industrial wastewater is emphasized. These findings enhance our understanding of the adsorption mechanism and underscore the fixed-bed column system's applicability in real-world scenarios, addressing environmental concerns related to heavy metal contamination of industrial effluents.

New trends in modelling of breakthrough curves to remove pollutants using adsorption on advanced monoliths geometries.

This work proposes a rigorous mathematical model capable of reproducing the adsorption process in dynamic regime on advanced monoliths geometries. For this, four bed geometries with axisymmetric distribution of channels and similar solid mass were proposed. In each geometry a different distribution of channels was suggested, maintaining constant the bed dimensions of 15 cm high and 5 cm radius. The mathematical modeling includes mass and momentum transfer phenomena, and it was solved with the COMSOL Multiphysics software using mass transfer parameters published in the literature. The overall performance of the column was evaluated in terms of breakthrough (CA/CA0 = 0.1) and saturation times (CA/CA0 = 0.9). The mass and velocity distributions obtained from the proposed model show good physical consistency with what is expected in real systems. In addition, the model proved to be easy to solve given the short convergence times required (2-4 h). Modifications were made to the bed geometry to achieve a better use of the adsorbent material which reached up to 80%. The proposed bed geometries allow obtaining different mixing distributions, in such a way that inside the bed a thinning of the boundary layer is caused, thus reducing diffusive effects at the adsorbent solid-fluid interface, given dissipation rates of about 323 × 10-11 m2/s3. The bed geometry composed of intersecting rings deployed the best performance in terms of usage of the material adsorbent, and acceptable hydrodynamical behavior inside the channels (maximum fluid velocity = 35.4 × 10-5 m/s and drop pressure = 0.19 Pa). Based on these results, it was found that it is possible to reduce diffusional effects and delimit the mass transfer zone inside the monoliths, thus increasing the efficiency of adsorbent fixed beds.

Efficient Mesoporous MgO/g-C3N4 for Heavy Metal Uptake: Modeling Process and Adsorption Mechanism.

Removing toxic metal ions arising from contaminated wastewaters caused by industrial effluents with a cost-effective method tackles a serious concern worldwide. The adsorption process onto metal oxide and carbon-based materials offers one of the most efficient technologies adopted for metal ion removal. In this study, mesoporous MgO/g-C3N4 sorbent is fabricated by ultrasonication method for the uptake Pb (II) and Cd (II) heavy metal ions from an aqueous solution. The optimum conditions for maximum uptake: initial concentration of metal ions 250 mg g-1, pH = 5 and pH = 3 for Pb++ and Cd++, and a 60 mg dose of adsorbent. In less than 50 min, the equilibrium is reached with a good adsorption capacity of 114 and 90 mg g-1 corresponding to Pb++ and Cd++, respectively. Moreover, the adsorption isotherm models fit well with the Langmuir isotherm, while the kinetics model fitting study manifest a perfect fit with the pseudo-second order. The as fabricated mesoporous MgO/g-C3N4 sorbent exhibit excellent Pb++ and Cd++ ions uptake and can be utilized as a potential adsorbent in wastewater purification.

Engineered pine nut shell derived activated carbons for improved removal of recalcitrant pharmaceuticals in urban wastewater treatment.

Novel powdered activated carbons (PACs) from pine cones and pine nut shells (PNSs) were tested for the competitive adsorption of pharmaceutical compounds (PhCs) in spiked (100 µg/L) secondary effluent and mixed liquor from an urban wastewater treatment plant. Steam activated PNS77, with hierarchical pore structure and 1463 m2/g of BET area, outperformed the commercial benchmark (WP220, mineral origin) for PhCs and dissolved organic matter (DOM) control. PNS77 attained the highest adsorption capacity and rate in synthetic and real wastewaters. Competitive adsorption isotherms revealed the detrimental effect of direct site competing DOM on PhC removal. The PhCs' adsorbability increased with their hydrophobicity, regardless of the water matrix. Kinetic data allowed inferring that indirect competition due to pore constriction/blockage appeared to occur only in mixed liquor. Adsorption isotherm data modelling for ng/L range revealed 80 % removal of carbamazepine and diclofenac would be achieved dosing 8-15 mg/L PNS77 to secondary effluent, while for mixed liquor the dose must be doubled to balance the increased competition. Hydrophilic sulfamethoxazole required a higher dose (34-44 mg/L), lower in the mixed liquor. PNS77 hierarchical pore network and basic surface chemistry minimized DOM direct site competition, requiring lower doses in practical applications for wastewater treatment.

Effective Adsorption of Congo Red from Aqueous Solution Using Fe/Al Di-Metal Nanostructured Composite Synthesised from Fe(III) and Al(III) Recovered from Real Acid Mine Drainage.

This study presents the first known exploration of Congo red dye (CR) adsorption by a polycationic Fe/Al Di-metal nanostructured composite (PDFe/Al) synthesised using Fe(III) and Al(III) recovered from authentic acid mine drainage (AMD). The PDFe/Al successfully removed CR from the aqueous solution. The mineralogical, microstructural, and chemical properties of the synthesised PDFe/Al adsorbent (before and after adsorption) were studied using state-of-the-art analytical instruments. The optimum conditions were observed to be 100 mg·L-1 CR, 1 g of the PDFe/Al in 500 mL adsorbate solution, 20 min of shaking, pH = 3-8, and a temperature of 35 °C. At optimised conditions, the PDFe/Al showed ≥99% removal efficacy for CR dye and an exceptionally high Langmuir adsorption capacity of 411 mg·g-1. Furthermore, a diffusion-limited adsorption mechanism was observed, with two distinct surfaces involved in the adsorption of CR from an aqueous solution. It was determined that the adsorption of CR induced internal strain and deformation within the matrices and interlayers of the PDFe/Al which resulted in a marked increase in the adsorbent pore surface area and pore volume. The remarkably high adsorption capacity could be attributed to the high surface area. A regeneration study showed that the adsorbent could be reused more than four times for the adsorption of CR. The findings from this study demonstrated the feasibility of recovering valuable minerals from toxic and hazardous AMD and demonstrated their potential for the treatment of industrial wastewaters.

Modelling peptide adsorption energies on gold surfaces with an effective implicit solvent and surface model.

The interaction of proteins and peptides with inorganic surfaces is relevant in a wide array of technological applications. A rational approach to design peptides for specific surfaces would build on amino-acid and surface specific interaction models, which are difficult to characterize experimentally or by modeling. Even with such a model at hand, the large number of possible sequences and the large conformation space of peptides make comparative simulations challenging. Here we present a computational protocol, the effective implicit surface model (EISM), for efficient in silico evaluation of the binding affinity trends of peptides on parameterized surface, with a specific application to the widely studied gold surface. In EISM the peptide surface interactions are modeled with an amino-acid and surface specific implicit solvent model, which permits rapid exploration of the peptide conformational degrees of freedom. We demonstrate the parametrization of the model and compare the results with all-atom simulations and experimental results for specific peptides.

A nappies management by-product for the treatment of uranium-contaminated waters.

The direct disposal of municipal solid waste such as nappies to the environment may create serious pollution problems. Based on the circular economy and waste management concepts, the conversion of nappies and/or their ingredients (such as super absorbent polymer (SAP)) to high added value products is of great importance. In this work, a modified SAP (MSAP) was examined as an adsorbent for treatment of contaminated waters and uranium recovery. Batch experiments and spectroscopic techniques were used to examine the effect of various parameters (pH, contact time, temperature, initial concentration, and ionic strength), and the mechanism of adsorption U(VI) and desorption process. The U(VI) concentration was determined by alpha spectroscopy after addition of 232U standard tracer solution to account for possible interferences during electrodeposition and alpha particle counting. The maximum adsorption monolayer capacity was found to be 217.4 mg/g at pH 4.0 and at 298 K. The adsorption of U(VI) on MSAP seems to occur mainly via the formation of inner-sphere surface complexes between U(VI) and the carboxylic surface moieties of MSAP. The MSAP could satisfactorily be regenerated with 0.1 M Na2CO3 (>90%) and it also shows a promising applicability to real wastewaters contaminated with U(VI).

Competition in chromate adsorption onto micro-sized granular ferric hydroxide.

Hexavalent chromium is highly toxic and elaborate technology is necessary for ensured removal during drinking water production. The present study aimed at estimating the potential of a micro-sized iron hydroxide (µGFH] adsorbent for chromate removal in competition to ions presents in drinking water. Freundlich and Langmuir models were applied to describe the adsorption behaviour. The results show a high dependency on the pH value with increasing adsorption for decreasing pH values. The adsorption capacity in deionized water (DI) at pH 7 was 5.8 mg/g Cr(VI) while it decreased to 1.9 mg/g Cr(VI) in Berlin drinking water (DW) at initial concentrations of 1.2 mg/L. Desorption experiments showed reversible adsorption indicating ion exchange and outer sphere complexes as main removal mechanisms. Competing ions present in DW were tested for interfering effects on chromate adsorption. Bicarbonate was identified as main inhibitor of chromate adsorption. Sulfate, silicate and phosphate also decreased chromate loadings, while calcium enhanced chromate adsorption. Adsorption kinetics were highly dependent on particle size and adsorbent dose. Adsorption equilibrium was reached after 60 min for particles smaller than 63 µm, while 240 min were required for particles from 125 µm to 300 µm. Adsorption kinetics in single solute systems could be modelled using the homogeneous surface diffusion model (HSDM) with a surface diffusion coefficient of 4∙10 -14 m2/s. Competitive adsorption could be modelled using simple equations dependent on time, adsorption capacity and concentrations only.

Modelling equilibrium adsorption of single, binary, and ternary combinations of Cu, Pb, and Zn onto granular activated carbon.

Elevated concentrations of heavy metals in water can be toxic to humans, animals, and aquatic organisms. A study was conducted on the removal of Cu, Pb, and Zn by a commonly used water treatment adsorbent, granular activated carbon (GAC), from three single, three binary (Cu-Pb, Cu-Zn, Pb-Zn), and one ternary (Cu-Pb-Zn) combination of metals. It also investigated seven mathematical models on their suitability to predict the metals adsorption capacities. Adsorption of Cu, Pb, and Zn increased with pH with an abrupt increase in adsorption at around pH 5.5, 4.5, and 6.0, respectively. At all pHs tested (2.5-7.0), the adsorption capacity followed the order Pb > Cu > Zn. The Langmuir and Sips models fitted better than the Freundlich model to the data in the single-metal system at pH 5. The Langmuir maximum adsorption capacities of Pb, Cu, and Zn (mmol/g) obtained from the model's fits were 0.142, 0.094, and 0.058, respectively. The adsorption capacities (mmol/g) for these metals at 0.01 mmol/L equilibrium liquid concentration were 0.130, 0.085, and 0.040, respectively. Ideal Adsorbed Solution (IAS)-Langmuir and IAS-Sips models fitted well to the binary and ternary metals adsorption data, whereas the Extended Langmuir and Extended Sips models' fits to the data were poor. The selectivity of adsorption followed the same order as the metals' capacities and affinities of adsorption in the single-metal systems.

Tetracycline adsorption onto activated carbons produced by KOH activation of tyre pyrolysis char.

Tyre pyrolysis char (TPC), produced when manufacturing pyrolysis oil from waste tyre, was used as raw material to prepare activated carbons (ACs) by KOH activation. KOH to TPC weight ratios (W) between 0.5 and 6, and activation temperatures from 600 to 800 °C, were used. An increase in W resulted in a more efficient development of surface area, microporosity and mesoporosity. Thus, ACs derived from TPC (TPC-ACs) with specific surface areas up to 814 m(2) g(-1) were obtained. TPC, TPC-ACs and a commercial AC (CAC) were tested for removing Tetracycline (TC) in aqueous phase, and systematic adsorption studies, including equilibrium, kinetics and thermodynamic aspects, were performed. Kinetics was well described by the pseudo-first order model for TPC, and by a pseudo second-order kinetic model for ACs. TC adsorption equilibrium data were also fitted by different isotherm models: Langmuir, Freundlich, Sips, Dubinin-Radushkevich, Dubinin-Astokov, Temkin, Redlich-Peterson, Radke-Prausnitz and Toth. The thermodynamic study confirmed that TC adsorption onto TPC-ACs is a spontaneous process. TC adsorption data obtained in the present study were compared with those reported in the literature, and differences were explained in terms of textural properties and surface functionalities. TPC-ACs had similar performances to those of commercial ACs, and might significantly improve the economic balance of the production of pyrolysis oil from waste tyres.