Temkin Isotherm Models Research Articles

Application of novel phytosorbent to sequester chromium(VI) and lead(II) from aqueous phase: Optimization, equilibrium and kinetics

AbstractThis study investigates the potential of Prosopis cineraria leaf powder (PCLP) as a biosorbent for removing heavy metal ions (HMIs) from aqueous solutions. The biosorption characteristics of PCLP were evaluated with respect to pH, contact time, initial concentrations, and biosorbent dosage. Equilibrium data were analyzed using Langmuir, Freundlich, Temkin, and Dubinin‐Radushkevich (D‐R) isotherm models. Langmuir isotherm demonstrated monolayer adsorption for Cr(VI) (R2 = 0.9876) and Pb(II) (R2 = 0.9990), with maximum adsorption capacities of 10.046 and 10.238 mg g−1, respectively. Kinetic analysis showed a good fit to the pseudo‐second‐order (PSO) model, with R2 values of 0.9979 for Cr(VI) and 0.9821 for Pb(II), indicating that H‐bonding and electrostatic interactions were the dominant adsorption mechanisms. Additionally, non‐linear regression analysis was performed to determine the best‐fitting equilibrium model and compared with linear isotherm and kinetic models. The results confirmed that the nonlinear method outperformed the linear method in isotherm analysis. Specifically, the nonlinear Temkin isotherm model exhibited stronger correlation with the experimental data, making it the most suitable model for fitting the equilibrium data. Conversely, the non‐linear pseudo‐second‐order models yielded comparable goodness of fit to the linear kinetic analysis results. Overall, the findings highlight PCLP as a promising, environmentally friendly, and cost‐effective biosorbent for the removal of toxic HMIs, contributing to sustainable environmental management.

Synthesis and Characterization of Phosphorus-Containing Sorbent for Basic Dye Removal.

A new phosphorus-containing sorbent was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) and trimethylvinyl silane (TMVS) with diphenylvinylphoshine oxide (DPVO). It was characterized and applied in the removal of cationic dyes such as C.I. Basic Yellow 2 (BY2), C.I. Basic Blue 3 (BB3) and C.I. Basic Red 46 (BR46) using the batch method. Spectroscopic analysis indicated that the phosphinoyl group was introduced into the sorbent structure. Equilibrium adsorption data were fitted to the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The Freundlich model is the most suitable to describe the adsorption of BB3 (the Freundlich constant kF = 32.3 mg1-1/nL1/n/g) and BY2 on the sorbent (13.8 mg1-1/nL1/n/g), while the Langmuir model is the most adequate to describe the adsorption of BR46 (the monolayer capacity Q0 = 2.7 mg/g). The kinetics of the dye adsorption follows the assumptions of the pseudo-second-order (the rate constants k2 = 0.087 ÷ 0.738 g/mg min) model rather than pseudo-first-order or intraparticle diffusion. The presence of Na2SO4 and cationic surfactant in the aqueous solutions inhibited dye retention by the DPVO-EGDMA-TMVS. Adsorbent regeneration efficiency does not exceed 60% using 1 M NaCl and 1 M HCl solutions in the presence of 50% v/v methanol.

Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Activated Charcoal as Methylene Blue Adsorbents

As novel methylene blue adsorbents, polyvinyl alcohol and activated charcoal were used to modify the surface of superparamagnetic iron oxide nanoparticles. The adsorption capacity after 69 h was 26.50 ± 0.99–40.21 ± 1.30 mg/g, depending on the temperature (333.15, 310.15, and 298.15 K) and the initial concentration of methylene blue, which was between 0.017 and 0.020 mg/mL. Based on thermodynamics parameters, the adsorption process can be considered to be spontaneous endothermic physisorption. Kinetics studies show that the pseudo-second-order model was the best-fitted model. Adsorption isotherm studies show that the best-fitted models were the Langmuir, Langmuir, and Temkin and Pyzhev isotherm models when adsorbing MB at 333.15, 310.15, and 298.15 K, respectively.

Removal of Ni(II), Cu(II), Pb(II), and Cd(II) from Aqueous Phases by Silver Nanoparticles and Magnetic Nanoparticles/Nanocomposites.

The intake of heavy metals into the body, even at very low concentrations, may cause a decrease in central nervous system functions; deterioration of blood composition; and liver, kidney, and lung damage. Therefore, heavy metal ions must be removed from water. In this study, silver, magnetic iron/copper, and iron oxide nanoparticles were synthesized using Lathyrus brachypterus extract and then Fe/Cu-AT, Fe3O4-AT, Fe/Cu-CS, and Fe3O4-CS magnetic nanocomposite beads were synthesized using alginate and chitosan. The removal of Cd(II), Pb(II), Ni(II), and Cu(II) ions from aqueous phases using synthesized nanoadsorbents was investigated by single and competitive (double and quaternary) adsorption techniques. The kinetic usability of the magnetic iron oxide chitosan (Fe3O4-CS) nanocomposite beads with the highest removal efficiency was evaluated. Based on experimental results, the order of removal was found to be 98.39, 75.52, 51.54, and 45.34%, and it was listed as Pb(II) > Cu(II) > Cd(II) > Ni(II), respectively. The Dubinin-Radushkevich, Freundlich, Langmuir, and Temkin isotherm models were used, and experimental results revealed that the experimental data fit the Langmuir model better. The maximum adsorption capacities (qm) obtained from the Langmuir isotherm model of Fe3O4-CS were found to be 8.71, 23.75, 18.57, and 12.38 mg/g for Ni(II), Pb(II), Cu(II), and Cd(II) ions, respectively. When the kinetic data were applied to the Lagergren, Ho-McKay, and Elovich models, it was observed that the adsorption kinetics mostly conformed to the Ho-McKay second-order rate equation. The binary and quaternary competitive adsorption data showed that Fe3O4-CS were selective toward Cu(II) and Pb(II). The reusability of the Fe3O4-CS nanoadsorbent was performed as three cycles with the same concentration. The adsorption capacities were found to be 95.81, 70.65, 50.50, and 42.75%, in turn for Pb(II), Cu(II), Cd(II), and Ni(II) ions after three cycles, which revealed that the Fe3O4-CS nanoadsorbent can be used after three cycles without losing its efficiency.

2-Methyl-4-chlorophenoxyacetic acid (MCPA) sorption and desorption as a function of biochar properties and pyrolysis temperature.

2-Methyl-4-chlorophenoxyacetic acid (MCPA) is a highly mobile herbicide that is frequently detected in global potable water sources. One potential mitigation strategy is the sorption on biochar to limit harm to unidentified targets. However, irreversible sorption could restrict bioefficacy thereby compromising its usefulness as a vital crop herbicide. This research evaluated the effect of pyrolysis temperatures (350, 500 and 800°C) on three feedstocks; poultry manure, rice hulls and wood pellets, particularly to examine effects on the magnitude and reversibility of MCPA sorption. Sorption increased with pyrolysis temperature from 350 to 800°C. Sorption and desorption coefficients were strongly corelated with each other (R2 = 0.99; P < .05). Poultry manure and rice hulls pyrolyzed at 800°C exhibited irreversible sorption while for wood pellets at 800°C desorption was concentration dependent. At higher concentrations some desorption was observed (36% at 50 ppm) but was reduced at lower concentrations (1-3% at < 5 ppm). Desorption decreased with increasing pyrolysis temperature. Sorption data were analyzed with Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. Freundlich isotherms were better predictors of MCPA sorption (R2 ranging from 0.78 to 0.99). Poultry manure and rice hulls when pyrolyzed at higher temperatures (500 and 800°C) could be used for remediation efforts (such as spills or water filtration), due to the lack of desorption observed. On the other hand, un-pyrolyzed feedstocks or biochars created at 350°C could perform superior for direct field applications to limit indirect losses including runoff and leaching, since these materials also possess the ability to release MCPA subsequently to potentially allow herbicidal action.

Design of acid-geopolymers based on clays by-products for methylene blue removal from wastewater

Morocco has significant phosphate reserves, but the extraction process generates a lot of waste rock. To tackle this problem, this study aims to make use of clay, a by-product of phosphate mining, to create acid-activated geopolymers. Four formulations of geopolymers were prepared by combining metakaolin (MK) and calcined clay (CC) in different proportions, which were then activated using phosphoric acid. Different techniques were performed for the characterization of raw and calcined clays as well as the elaborated geopolymers. Based on the XRD, FTIR, and SEM results, it was observed that an increase in the level of CC replacing MK led to the formation of new crystals like Monetite, Newberyite, and Brushite. The quantity of CC influenced the type of crystals formed. Moreover, the specific surface area analysis revealed that the geopolymer (GP2) containing 25% of CC exhibited the highest specific surface area. These materials were then tested for their ability to eliminate methylene blue (MB) from wastewater. The results indicated that GP2, a geopolymer made with 75% MK and 25% CC had the highest efficiency in removing MB with a rate of 98%. The material was highly reactive and achieved adsorption equilibrium in just 15 minutes. It was found to be effective in both acidic and alkaline environments. Furthermore, studies have shown that the Temkin isotherm model best explains how MB (a dye) is absorbed by GP2, with a high correlation coefficient. Additionally, the pseudo-second-order kinetic model was a better fit, suggesting that chemical interactions are more significant than physical interactions. Notably, the use of phosphoric acid to activate GP2 was found to selectively adsorb cationic dyes.

Optimization of the removal of the antibiotic ciprofloxacin by composite aerogels based on PVA/agar/maltodextrin

In this study, we used a synthetic aerogel based on PVA/agar/maltodextrin to remove the antibiotic ciprofloxacin (CFX) from aqueous media. Response surface method (RSM) is used to study the relationship between the factors affecting the adsorption process, thereby optimizing the adsorption efficiency, and making decisions on improving the adsorption process better sub. The research results obtained are as follows: pH2, initial CFX concentration 51 mg L−1, adsorbent dosage 0.16 g L−1, adsorption time 120 min, and temperature 51.5 °C reached the maximum adsorption capacity. The maximum additive is 38.63 mg g−1. The experimental data agree with the pseudo-quadratic kinetic model and the Langmuir and Temkin isotherm models. The composite aerogel adsorbent (AE) in this study is a potential candidate for adsorbent to remove antibiotic contamination in aqueous media.

Evaluation of efficiency of Wheat straw nanocellulose as nanoadsorbent for the removal of divalent copper, lead and zinc from aqueous solution

Novel nanocellulose (cellulosic carbohydrate polymer) embedded with Wheat straw was synthesized, characterized and examined as nanoadsorbent for the removal of copper, lead and zinc metals from aqueous solution through batch mode. The effects of pH, dose, contact time, temperature and synchronous cations on the amount of Cu (II), Pb (II) and Zn (II) adsorbed have been probed. The desirable pH was 8 and nanoadsorbent dose was 0.6 g/50 mL in the adsorption study. The removal efficiencies of Cu (II), Pb (II) and Zn (II) were 88.75%, 81.18%, 86.84% respectively. Adsorption kinetic study was employed to analyze experimental data and adsorption process followed pseudo second order kinetic model. Langmuir, Freundlich, Temkin and Redlich-Peterson isotherm models were used to indicate the adsorption of Cu (II), Pb (II) and Zn (II) on WSN and thermodynamic study affirmed that adsorption process was endothermic and spontaneous. AFM indicated size and morphology and attachment of functional groups on WSN were examined by FTIR. The results confided that adsorption is economically competent method for removing Cu (II), Pb (II) and Zn (II) and WSN is anticipative owing to its ease and low cost of regeneration

Adsorption of anionic dye from aqueous environment using surface-engineered Zn/Cu hydroxy double salt-based material: mechanistic, equilibrium and kinetic studies.

Herein, ethylene glycol (EG)-modified Zn/Cu hydroxy double salts (HDS) were synthesized using a facile synthetic approach. The formation of layered structure and presence of EG in the interlayer region were confirmed using PXRD and FTIR techniques. Furthermore, XPS analysis was used to confirm presence of metal ions in synthesized HDS. The surface area and pore size diameter of the HDS was found to be 32.30 m2 g-1 and 2.22 nm, respectively, using BET. The role of HDS was evaluated for its potential application as a sorbent for Congo red (CR) dye uptake. Batch studies were conducted to examine the impact of key variables, i.e., pH, time, adsorbent dosage and dye concentration on adsorption efficiency of HDS. Linear-nonlinear isotherm and kinetic models were employed for detailed analysis of experimental data. Langmuir, Freundlich and Temkin isotherm models were subsequently utilized to fit equilibrium data, among which Langmuir demonstrated to be most accurate. The maximum monolayer adsorption capacity estimated using Langmuir model was computed to be 181.81 mg g-1. The kinetic data follows pseudo-second-order model having good R2 value (0.999). Additionally, thermodynamic study suggested spontaneous and endothermic nature of adsorption process having reusability up to 5 cycles with removal efficiency more than 85%.

Efficient Removal of Pb2+, Cu2+ and Zn2+ by Waste Tea‐Derived Cost‐Effective Bioadsorbent

AbstractThis study examined the potential of waste tea as an adsorbent for the removal of Pb2+, Cu2+, and Zn2+ ions from contaminated water. The study analyzed the effect of various factors, including adsorbent dose (1–6 g), NaOH concentration (0.5–1.5 %), pH (3–8), shaking time (1–4 h), shaking speed (220 rpm and 320 rpm), temperature (25–50 °C), and particle size (300–710 μm), on the adsorption of ions on waste tea. The experiment‘s findings revealed that the removal of Pb+2 with a waste tea‐derived adsorbent was more significant than that of Cu2+, and Zn2+. Instrumental techniques such as FTIR, SEM, XRD, TGA, and ICPMS were used to characterize the adsorbent. Additionally, Langmuir, Freundlich, and Temkin isotherm models were employed to explain the equilibrium isotherm data of Pb2+, Cu2+, and Zn2+ ions. Furthermore, the adsorption kinetics data for these heavy metal ions were found to fit a pseudo‐second‐order model. The study found waste tea to be a low‐cost, eco‐friendly, and easily obtainable natural adsorbent for eliminating heavy metal ions from aqueous solutions. Additionally, the study showed that waste tea was effective in removing 98.43 % of Pb2+, 73.22 % of Cu2+, and 88.37 % of Zn2+ ions from aqueous solutions.

Adsorptive removal of Cr (VI) from aqueous solution using laboratory prepared ZnO nanoparticles

Nano sized zinc oxide (ZnO) been successfully prepared in laboratory by precipitation technique. As prepared ZnO materials were characterized by XRD and SEM analyses. The XRD pattern showed the crystallinity of the material and average crystallite size was found to be 16.61 nm. The SEM images of ZnO nanoparticle revealed that it was flakes like structure having smooth texture. Batch adsorption experiments were performed to investigate the percentage removal of Cr (VI) from aqueous solution. The effects of Cr (VI) concentration, pH of solution, adsorbent dose and contact time variations were studied in order to have adsorptive efficiency of as prepared ZnO nanoparticles. The optimum contact time for maximum adsorption was found to be 90 minutes. The optimum pH was found to be 2.0 at an initial concentration of 20 mg/L. Similarly, the optimum dose of ZnO for the adsorption of Cr (VI) was found to be 0.4 g. The adsorption properties of ZnO were then evaluated by using Langmuir, Freundlich and Temkin isotherm models. The maximum adsorption capacity (Qm) was found to be 3.43 mg/g which is in good agreement with literature value. The correlation value showed that Langmuir isotherm model was found to be more favorable than Freundlich and Temkin adsorption isotherm model, indicating the presence of homogeneous equivalent active sites in ZnO with monolayer adsorption.

Improved methylene blue adsorption from an aqueous medium by ozone-triethylenetetramine modification of sawdust-based biochar

In this study, sawdust biochar-O3-TETA (SDBT), a novel biochar, was prepared via treatment with 80% sulfuric acid, followed by oxidation by ozone and subsequent treatment with boiling Triethylenetetramine (TETA). Characterization studies of the prepared SDBT adsorbent were performed with SEM–EDX, BET, XRD, BJH, FT-IR, DTA and TGA analyses. The adsorption efficiency of MB dye by SDBT biochar from water was investigated. Methylene Blue (MB) dye absorption was most effective when the solution pH was 12. The maximum removal % of MB dye was 99.75% using 20 mg/L as starting MB dye concentration and 2.0 g/L SDBT dose. The Qm of the SDBT was 568.16 mg/g. Actual results were fitted to Temkin (TIM), Freundlich (FIM), and Langmuir (LIM) isotherm models. The experimental results for SDBT fitted well with all three models. Error function equations were used to test the results obtained from these isotherm models, which showed that the experimental results fit better with TIM and FIM. Kinetic data were investigated, and the pseudo-second-order (PSOM) had R2 > 0.99 and was mainly responsible for guiding the absorption rate. The removal mechanism of the MB dye ions in a base medium (pH 12) may be achieved via physical interaction due to electrostatic interaction between the SDBT surface and the positive charge of the MB dye. The results show that SDBT effectively removes the MB dye from the aqueous environment and can be used continually without losing its absorption efficiency.

Guar Gum as an Eco-Friendly Corrosion Inhibitor for N80 Carbon Steel under Sweet Environment in Saline Solution: Electrochemical, Surface, and Spectroscopic Studies.

In this study, the corrosion inhibition performance of the natural polysaccharide guar gum (GG) for N80 carbon steel in CO2-saturated saline solution at different temperatures and immersion times was investigated by weight loss and electrochemical measurements. The results have revealed that GG showed good inhibition performance at lower and higher temperatures. The inhibition efficiency observed via weight loss measurements reached 76.16 and 63.19% with 0.4 g L-1 of GG, at 25 and 50 °C, respectively. The inhibition efficiency of GG increased as the inhibitor concentration and immersion time increased but decreased with increasing temperature. EIS measurements have shown that, even after prolonged exposure, GG was still able to protect the metal surface. Potentiodynamic measurements showed the mixed-type nature of GG inhibitive action. The Temkin and Dubinin-Radushkevich adsorption isotherm models give accurate fitting of the estimated data, and the calculated parameters indicated that the adsorption of GG occurred mainly via an electrostatic or physical adsorption process. The associated activation energy (Ea) and the heat of adsorption (Qa) supported the physical adsorption nature of GG. FTIR analysis was used to explain the adsorption interaction between the inhibitor and the N80 carbon steel surface. SEM-EDS and AFM confirmed the adsorption of GG and the formation of an adsorptive layer of GG on the metal surface.

Biosorption of Cu (II) and Pb (II) ions using acid modified Senna tora pods with a focus on isotherms and kinetics studies

The removal of heavy metals by biosorption method using agricultural waste and plant materials has become a powerful technology that is been explored for the treatment of domestic and industrial waste water due to its easy operating requirements and low cost. This work reports the application of Senna tora pods for the elimination of heavy metals (Cu and Pb ions) by biosorption in batch system. The effects of pH, contact time, dosage and initial concentration were evaluated. The kinetic and isotherms models for the Cu(II)/Pb(II) biosorption were tested basically by the pseudo-first-order and pseudo-second order kinetic models. Langmuir, Freundlich and Temkin isotherms models have also been used to fit equilibrium adsorption data. The monolayer sorption capacity (qL) of Cu(II) was found to be 0.791 mg/g while that of Pb(II) was 0.51 mg/g.The low Langmuir constant (KL) values suggests that the adsorption process was largely due to physisorption mechanism. The adsorption kinetics follow a pseudo-first-order model for Cu(II) and pseudo-second-order model for Pb(II), and the equilibrium data is suitably fitted by the Langmuir models than the Freundlich due to the high R2 values of 0.989 and 0.97 for Cu(II) and Pb(II) ions respectively. Consequently, there exists a closeness of the calculated sorption capacity (qcal) to the experimental sorption capacity (qex). In conclusion, the study generally showed that Senna tora pods is a potential and efficient adsorbent that could be explore for the bioremediation of heavy metal contaminated industrial wastewater.

Fabrication of versatile Ag-P/Ppy core-shell nanocomposite: Adsorption efficacy for chromium (VI) removal and assessment of antioxidant and antibacterial activities

This study reports the synthesis, via in-situ chemical oxidative polymerisation, of conducting polymer-based silver phosphate Polypyrrole (Ag-P/Ppy) core-shell nanocomposite, exhibiting antioxidant and antibacterial characteristics, for the adsorption of chromium (VI) ions from aqueous solutions. Filtering away Cr (VI) ions efficiently also improves the filtered water with antibacterial and antioxidant properties. P-XRD, ATR-FTIR, FESEM, EDAX, TEM, zeta potential, TGA, and BET studies characterized Ag-P/Ppy. The core-shell nanostructure of Ag-P/Ppy was determined by TEM micrographs, which indicated the presence of an Ag-P core and a Ppy shell. pH value, adsorbent dose, stirring rate, contact time, and Cr (VI) pollutant concentration, were investigated as potential influencing factors. At pH 2, 99.4 % of Cr(VI) was removed in 55 min. The adsorption kinetics was effectively depicted by a pseudo-second-order kinetics model, signifying that chemisorption played a momentous role in the total adsorption capacity. Freundlich, Temkin, Redlich-Peterson, and Sips isotherm models were fitted to adsorption data. Temkin and Redlich-Peterson models have a higher (0.99) correlation coefficient than Freundlich (0.95) and Sips (0.98). The maximum adsorption capacity (qm) evaluated using the Sips model was 138.5 mg g−1, which was quite close to the 130.55 mg g−1 value obtained from experiments. The manufactured nanocomposite showed 91.2 % radical scavenging activity in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Antibacterial activity of the Ag-p/Ppy core-shell nanocomposite contrary to gram-positive (S. aureus) and gram-negative (P. aeruginosa, E. coli, and K. pneumoniae) bacteria was assessed by means of the agar well diffusion technique. Compared to the positive control, it inhibited S. aureus, E. coli, K. Pneumoniae, and P. Aeruginosa by 82.35 %, 79.5 %, 63.63 %, and 76.7 % respectively. Therefore, the Ag-P/Ppy core-shell nanocomposite has the potential as a potent and versatile adsorbent for the exclusion of Cr (VI) ions from water.

RSM optimization studies for cadmium ions adsorption onto pristine and acid-modified kaolinite clay

Clay has been reported as an active absorbent for the removal of toxic heavy metals from aqueous medium. In this study, pristine and acid modified kaolinite clays (PKC and AMKC) were prepared, characterized using various analyses, and tested for Cd2+ ion adsorption from textile industry wastewater. After acid modification, the specific surface area of clay increased from 84.2 to 389.4 m2/g. Adsorption isotherm, kinetics and thermodynamics behaviour process were examined. The pH at (pHpzc) of 8.5 indicate that AMKC surface is positively charged for pH below the pHpzc attracting anions. Response surface methodology was used to investigate the effect of adsorption process factors on Cd2+ ion removal uptake. At the optimum process conditions of 45.3 °C temperature, 0.63 g/L adsorbent dosage, and 120.9 min contact time, the percentages of Cd2+ adsorbed by PKC and AMKC were 77.82% and 99.19%, respectively. Various models were employed to analyzed the kinetic and equilibrium data. The Pseudo-first order, Pseudo-second order and Intra-particle diffusion were used to evaluate the kinetic data, while the Langmuir, Freundlich and Temkin isotherm models were applied to analyzed the equilibrium data. The sorption kinetics was found to be best described by Pseudo-second order considering the high correlation coefficient (R2), smaller Chi-square (ᵪ2) and sum of square error (SSE). The Freundlich model was the most accurate in describing the equilibrium data followed by Langmuir and Temkin respectively. The thermodynamic reveal that the reaction is spontaneous and endothermic in nature, and increase in randomness between the adsorbent and adsorbate. The obtained activation energy (Ea) value suggest that the adsorption mechanism of Cd(II) is a physisorption dominated.

Effect of Different Modification Methods on the Adsorption of Manganese by Biochar from Rice Straw, Coconut Shell, and Bamboo.

The adsorption capacity of pristine biochar without modification is usually low. In this experiment, we comprehensively evaluated the adsorption of Mn(II) by biochar with different modification methods from different biomass. The biochar from rice straw, coconut shell, and bamboo was produced by pyrolysis at 600 °C under nitrogen and then modified with HNO3, NaOH, and Na2S, respectively. The results showed that the adsorption capacities of these modified biochar samples were in the order Biochar-NaOH > Biochar-Na2S > Biochar-HNO3. Among the three modification methods, biochar modified with NaOH is the optimum for the adsorption of Mn(II). However, the same method of modification has different effects on different biomass feedstocks. Rice straw: R-C > R-NaOH-C > R-Na2S-C > R-HNO3-C; coconut shell: C-NaOH-C > C-Na2S-C > C-HNO3-C > C-C; bamboo: B-NaOH-C > B-Na2S-C > B-C > B-HNO3-C. At the pH of 5 and 30 °C, R-C, C-NaOH-C, and B-NaOH-C showed the highest maximum adsorption capacity for Mn(II). Equilibrium data were evaluated by Langmuir, Freundlich, and Temkin isotherm models, and the results suggested that the Langmuir model is the most suitable to expound the adsorption behavior of Mn(II) on R-C, C-NaOH-C, and B-NaOH-C. Overall, the results from this work suggest that the key for preparing biochar adsorbents with high capacity is to choose the appropriate biomass feedstock and modification method.

Rice Husk for Adsorbing Dyes in Wastewater: Literature Review of Agricultural Waste Adsorbent, Preparation of Rice Husk Particles, Particle Size on Adsorption Characteristics with Mechanism and Adsorption Isotherm

This study aims to evaluate the adsorption characteristics of unmodified natural rice husk particles (sizes of 74, 177, and 500 μm) in adsorbing dyes in wastewater. The adsorption isotherm analysis was performed in batch mode. Turmeric was selected as a model for organic dyes. Ten isotherm models were used to predict and determine the characteristic parameters: Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Flory-Huggins, Fowler-Guggenheim, Hill-de-Boer, Jovanovic, Harkin Jura, and Halsey isotherm models. The adsorption isotherm analysis showed the phenomena that occur during adsorption are physical, with multilayer formation on the surface of the adsorbent and the occurrence of adsorbate-adsorbate repulsive interaction. The pore-filling molecules occur at the largest and medium particle sizes, whereas the small particle size has no pore-filling molecules. This study reveals that the natural rice husk (unmodified) could be employed as a low-cost and effective sorbent for wastewater treatment, supporting current issues in the Sustainable Development Goals (SDGs).

Enhanced Adsorption of Methylene Blue Using Phosphoric Acid-Activated Hydrothermal Carbon Microspheres Synthesized from a Variety of Palm-Based Biowastes

In the present study, the ability for novel carbon microspheres (CMs) derived from date palm (Phoenix dactylifera) biomass using a hydrothermal carbonization (HTC) process and activated using phosphoric acid to remove methylene blue dye was investigated. Three types of palm-based wastes (seeds, leaflet, and inedible crystallized date palm molasses) were used and converted to CMs via the HTC process. The prepared samples were then activated using phosphoric acid via the incipient wetness impregnation method. The CMs samples before and after activation were analyzed using scanning electron microscopy (SEM), elemental analysis and scanning (CHNS), and the Fourier transform infrared (FTIR) and Brunauer–Emmet–Teller (BET) methods. The samples exhibited high BET surface areas after activation (1584 m2/g). The methylene blue adsorption results showed good fitting to the Langmuir, Fruendlich, and Temkin isotherm models for all activated samples. The maximum adsorption capacity achieved was 409.84 mg/g for activated CM obtained from the palm date molasses, indicating its high potential for application as a dye-based adsorption material.

The application of Rumex abyssinicus based activated carbon for Brilliant Blue Reactive dye adsorption from aqueous solution

The environmental pollution and human health impacts associated with the discharge of massive dye-containing effluents necessitate a search for cost-effective treatment technology. Therefore, this research work is conducted with the objective of investigating the potential of Rumex abyssinicus-derived activated carbon (RAAC) for the adsorption of Brilliant Blue Reactive (BBR) dye from aqueous solutions. Chemical activation with H3PO4 followed by pyrolysis was used to prepare the adsorbent. Characterization of the developed adsorbent was done using proximate analysis, pH point of zero charge (pHpzc), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), Brunauer, Emmett, and Teller (BET), and X-ray diffraction (XRD). The experimental design and the effect of independent variables including pH (2, 6, and 10), initial dye concentration (50, 100, and 150 mg/L), adsorbent dosage (0.05, 0.1, and 0.15 g/100 mL), and contact time (20, 50, and 80 min) were optimized using the response surface methodology (RSM) coupled with Box Behnken design (BBD). The analysis results revealed the exitance of high specific surface area of 524 m2/g, morphological cracks, and the presence of multiple functional groups like –OH, C=C, alkene, and amorphous structure. Maximum removal efficiency of 99.98% was attained at optimum working conditions of pH 2, contact time of 50 min, dye concentration of 100 mg/L, and adsorbent dosage of 0.15 mg/100 mL, reducing the pollutant concentration from 100 to 0.02 mg/L. Evaluation of the experimental data was done using Langmuir, Freundlich, Temkin, and Sips isotherm models, in which the Langmuir model was found to be the best fit with the experimental data at R2 0.986. This shows that the adsorbent surface is homogeneous and mono-layered. Furthermore, the kinetic study confirmed that the pseudo second-order model best describes the experimental data with R2 = 0.999. In general, the research work showed that the low cost, environmental friendliness and high adsorption capabilities of the activated carbon derived from Rumex abyssinicus could be taken as an effective nt for the removal of BBR dye from aqueous solutions.