Study on the Physical Chemistry,Equilibrium, and Kinetic Mechanism of Azure A Biosorption by Zea Mays Biomass

The mechanism of Azure A (AA) biosorption by Zea mays biomass (ZMB) was studied. Surface chemistry and morphology were characterized by potentiometric titration, pH of zero charge, FTIR, and microscope analysis. The equilibrium data was modeled by Langmuir, Freundlich, Redlich-Peterson, Temkin, and multilayer models. AA biosorption was mainly limited by chemisorption, but the role of intraparticle diffusion could not be neglected. The integrative analysis of surface chemistry/biosorption studies showed that chemisorption, ion exchange, complexation, and/or electrostatic attraction were involved during AA biosorption. The maximum biosorption capacity of ZMB (q 5.84 mg/g) was registered at pH 7.6.      

Adsorption of Cd(II) Ions onto Activated Carbon Prepared from Hazelnut Husks

In this study, a batch adsorption of Cd(II) ions onto activated carbon (AC) produced from hazelnut husks were investigated. The factors controlling the adsorption process such as initial pH, agitation time, dosage and initial concentration have been examined. The AC was showed a high affinity to Cd(II) ions at pH values between 5.0 and 7.0. The equilibrium time was found to be 300 minutes. Cd(II) adsorption equilibrium was analyzed with both Langmuir and Freundlich isotherm equations and it was found that Langmuir equations fitted well with the experimental data. Maximum Cd(II) adsorption capacity of AC was calculated to be 20.9 mg g^?1. Cd(II) adsorption kinetics described well with the pseudo second order model. The activated carbon prepared from hazelnut husks is efficient sorbent material for the removal of Cd(II) ions from aqueous solutions.     

Removal of copper(II) from aqueous solution with rape stalk modified by citric acid

In this paper, rape stalk was modified with citric acid (CA) to prepare copper ion biosorbent. The modified rape stalk (MRS) was characterized by Fourier transforms infrared (FTIR), zeta potential, and thermogravimetric analysis (TGA). The effects of various parameters like initial Cu²⁺ concentration, contact time, initial pH, and temperature on adsorption capacity were studied. The adsorption capacity of MRS at 298 K was 69.84 mg/g, far higher than 18.24 mg/g for native rape stalk (NRS). The adsorption mechanism was also evaluated in terms of kinetics and thermodynamics. The adsorption equilibrium data was well described by the Langmuir isotherm model. The adsorption process followed the pseudo-second-order rate kinetics. Thermodynamic study showed spontaneous and endothermic nature of the adsorption process. The ion exchange of the adsorption mechanism was affirmed. MRS could be a potentially low-cost and green adsorbent for removal of Cu²⁺ from aqueous solution.     

Adsorptive Removal of Thorium(IV) from Aqueous Solutions Using Synthesized Polyamidoxime Chelating Resin: Equilibrium,Kinetic, and Thermodynamic Studies

In this study, an amidoximated chelating ion exchange resin was prepared by poly-acrylonitrile (PAN) grafted potato starch. The adsorbent characterizations such as specific surface area, pore volume, average pore radius, and Fourier transform infrared (FTIR) spectrum of the resin were measured. The effects of pH, adsorbent dosage, contact time, initial concentration of thorium ion, and temperature on adsorption of thorium ion from aqueous solutions were investigated. Four isotherm models including Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin were applied to analyze the equilibrium isotherm data. The results showed that Langmuir and Temkin models had a good agreement with experimental data. The maximum capacity of the adsorbent using the Langmuir isotherm model was 227.27 mg · g^?1. The kinetic models like pseudo-first-order, pseudo-second-order, Elovich, and intraparticle were examined to describe the adsorption process. The kinetics of the adsorption process was found to follow the pseudo-second-order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) were also calculated using equilibrium constant values at various temperatures (25, 35, 45, 55°C) and the positive value for ΔH° showed an endothermic adsorption process. The study suggests that the prepared adsorbent has promising potential for the removal of thorium from wastewaters.      

Manganese Biosorption from Aqueous Solution by Penicillium camemberti Biomass in the Batch and Fix Bed Reactors: A Kinetic Study

Biosorption of manganese(II) using suspended and immobilized cells of fungal Penicillium camemberti (biomass) and nano-P. camemberti (nano-biomass) was studied by evaluating the physicochemical parameters of the solution such as initial manganese ion concentration, pH, temperature, dosage, and contact time in both batch system and fixed bed column. The maximum biosorption obtained from the batch process was 91.54 and 71.08 % for nano-biomass and biomass in initial concentration of 5 ppm, respectively. The Langmuir, Freundlich, Temkin, and BET isotherms isotherm models were used in the equilibrium modeling. The correlation coefficient of more than 0.90 turned out that the adsorption process of Mn(II) on biomass and nano-biomass were in accordance with both Langmuir and Freundlich isotherms. The sorption process followed a second-order rate kinetics indicating the process to be diffusion controlled. The results also demonstrate that an intra-particle diffusion mechanism plays a significant role in the sorption process. The structure of P. camemberti was characterized by FT-IR spectrums.     

Evaluation of Pomegranate (Punica Granatum L.) Pulps for the Removal of Copper(II) Ions: Kinetic,Equilibrium, and Desorption Studies

Pomegranate pulp has been used as novel adsorbent for removing Cu(II) ions from aqueous solution. The optimum conditions for removal of Cu(II) ions were found to be pH 5.32, biosorbent dose 0.1 g, contact time 120 minutes, initial concentration 50 mg/L, and temperature 30°C. The kinetic data were well fitted to the pseudo-second-order model. The biosorption process agreed with the Langmuir isotherm model. Maximum monolayer biosorption capacity was 7.30 mg/g. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic. Desorption studies were carried out with different desorbing agents.      

Removal of methylene blue by seed-watermelon pulp-based low-cost adsorbent: Study of adsorption isotherms and kinetic models

Based on the abundance of seed-watermelon pulp (SWP) in Xinjiang, China, SWP was employed to prepare low-cost adsorbent toward the removal of methylene blue (MB). The effects of contact time at different initial concentration were studied. The widely used adsorption isotherm models including Langmuir, Freundlich, and Temkin isotherms were employed to depict the adsorption process. The Langmuir isotherm was best fitted to the experimental data. Batch kinetic studies showed that an equilibrium time of 300 minutes was needed for the adsorption. The adsorption properties can be well described by pseudo-second-order kinetic model and the MB uptake was not controlled by intraparticle diffusion mechanism.     

Waste-activated sludge (WAS) as Cr(III) sorbent biosolid from wastewater effluent

A biological sludge – waste-activated sludge (WAS) – from a dairy filtering station was investigated for the removal of trivalent chromium from aqueous solution. Kinetic results revealed that chromium adsorption was instantaneous. The removal rate increases up to pH 4 for contact times beyond 20 min. The equilibrium state is attained in 30 min in all the considered systems. The reaction orders as well as the diffusion rate constant were determined. Values adsorption isotherms measured at pH 3 generally followed the Langmuir model. The maximum uptake capacity was 25.64 mg/g. Values of thermodynamic parameters show that chromium (III) sorption on WAS is an exothermic process.This study provides an opportunity for the removal of heavy metals such as chromium from aqueous solutions using a low-cost biosolid as adsorbent support.     

Kinetic and isotherm studies of Cu(II) adsorption onto H3PO4-activated rubber wood sawdust

Adsorption of Cu(II) from aqueous solution onto H(3)PO(4)-activated carbon using rubber wood sawdust (RSAC) was investigated in a batch system. Kinetic and isotherm studies were carried out by considering the effects of various parameters, such as initial concentration, contact time, pH, and temperature. The optimal pH value for Cu(II) adsorption onto RSAC was found to be 6.0. Thermodynamic parameters such as standard Gibbs free energy (DeltaG(0)), standard enthalpy (DeltaH(0)), and standard entropy (DeltaS(0)) were evaluated by applying the Van't Hoff equation. The thermodynamics of Cu(II) adsorption onto RSAC indicates its spontaneous and exothermic nature. Langmuir, Freundlich, and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The Langmuir isotherm fits the experimental data significantly better than the other isotherms. Adsorption kinetics data were tested using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The initial sorption rate, pseudo-first-order, pseudo-second-order, and intraparticle diffusion rate constants for different initial concentrations were evaluated and discussed. Adsorption mechanism studies revealed that the process was complex and followed both surface adsorption and particle diffusion. The rate-controlling parameter and effective diffusion coefficient were determined using the Reichenberg plot. It was found that the adsorption occurs through film diffusion at low concentrations and at higher concentration the particle diffusion becomes the rate-determining step.     

Equilibrium,kinetic and thermodynamic biosorption studies of Hg(II) on red algal biomass of Porphyridium cruentum

Among a variety of microbial materials employed for biosorption, algae have added advantages of non-toxic and autotrophic nature. In this study, biosorption of Hg(II) was studied with red algal biomass of Porphyridium cruentum. The parameters affecting biosorption such as dosage of biosorbent, pH, contact time, initial metal concentration, temperature and effect of foreign metal cations in binary system were evaluated. Kinetic data were described with the help of pseudo-first-order and pseudo-second-order kinetic models. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models were applied to adsorption equilibrium data. According to the results, the maximum removal capacity (q_max) was 2.62?mg/g observed at pH 7 with 0.25?g/L of biosorbent dosage for Hg(II) solution containing 10?mg/L of metal ions. The Langmuir isotherm model fits best to the adsorption data while the kinetic data followed the pseudo-second-order model. Thermodynamics studies showed that the biosorption process of Hg(II) on P. cruentum was exothermic in nature.     

树脂吸附法豆腐柴叶果胶提取液脱色的研究(□)D3520树脂对色素的吸附性能

以大孔吸附树脂D3520对豆腐柴叶色素的吸附行为为研究对象,对色素的吸附平衡和吸附动力学进行研究,以Langmuir公式拟合25□下的吸附等温线,结果表明:D3520树脂对色素吸附规律较好的符合Langmuir吸附等温式.     

Dynamic and Rheological Properties of Span 80 at Liquid–Liquid Interfaces

The adsorption characteristics of Span 80 at liquid/liquid interfaces were investigated. The equilibrium interfacial tension values were successfully fitted with a Langmuir isotherm resulting in the determination of a mean molecular area from 25 to 35 Å²/mol. The measured interfacial tension values and deduced adsorption parameters depend on the experimental technique used to obtain them, either Du Noüy ring or profile analysis tensiometry. Two possible explanations to such phenomenon are provided. Adsorption kinetics of Span 80 at liquid/liquid interfaces were studied, and it was concluded that the diffusion of Span 80 molecules from the bulk is the rate determining step of the adsorption. Finally the interfacial rheology properties were investigated and compared to the Lucassen–van den Tempel model. A good match was obtained when the isotherm parameters determined by profile analysis tensiometry were used.      

Adsorption of toxic metals by natural and modified clinoptilolite

The chromium, cobalt and lead removal from aqueous solution by natural and modified zeolites was examined by using a batch-type method. Clinoptilolite samples used in this study were supplied from Bigadi?, Turkey. All samples were modified with HNO3 or NaOH to improve the adsorption capacity for heavy metals. The removal efficiencies and kinetics of heavy metals such as chromium, cobalt and lead on natural and modified zeolites were determined. The effects of the initial metal concentration on the removal percentage of heavy metal ions were studied. Freundlich and Langmuir isotherm constants and correlation coefficients were found and the equilibrium process was described by the Freundlich isotherm. The adsorption kinetic was tested and then it indicates the process to be diffusion controlled.     

Adsorption of Bismarck Brown by Iron Oxide Nanosphere and Its Modified Form

In the present study, adsorption of Bismarck Brown (BB) dye onto iron oxide nanospheres (IONs) and modified IONs by HCl from aqueous solution was investigated. The IONs was synthesized by solvothermal method and then modified by HCl. The high magnetic properties of both adsorbents lead to facial separation from aqueous solution by an external magnet. The results show that the modification of adsorbent cause higher adsorption capacity for removal of BB from aqueous solution. The prepared adsorbents were characterized by SEM, XRD, FTIR, and ATR-IR techniques. The adsorption kinetic and equilibrium data were fitted with different models. The results show that the equilibrium and kinetic data were best fitted with Langmuir–Freundlich isotherm and fractal-like pseudo-second-order kinetic model, respectively. The effects of pH and temperature have also been investigated.     

Optimization of Copper and Lead Removal by a Novel Biosorbent: Cucumber (Cucumis Sativus) Peels—Kinetic,Equilibrium, and Desorption Studies

Cucumber peels biosorption efficiency for copper(II) and lead(II) was studied in batch mode. The optimum conditions for removal of Cu(II) and Pb(II) ions were found to be pH 5.0, biosorbent dose of 0.1 g, contact time of 60 and 85 minutes, and initial concentration of 100 and 150 mg/L, respectively. The kinetic data were best described by pseudo-second order model. The biosorption process followed by the Langmuir isotherm model. Maximum monolayer biosorption capacities were 88.50 and 147.06 mg/g for Cu(II) and Pb(II) ions, respectively. Thermodynamic parameters suggest that the biosorption process is spontaneous and endothermic. Desorption studies were carried out with different desorbing agents.     

How does mechanism of biosorption determine the differences between the initial and equilibrium adsorption states?

The analysis of various models assumed to represent the influence of pH on heavy metals biosorption equilibrium is presented. It shows that all of them lead to the same mathematical expressions (e.g. the Langmuir or the Flory adsorption isotherm equations) when the pH effects are neglected. Even if considering the pH effects, some of them (competitive adsorption and ion-exchange models, for instance) still lead to analogical expressions for sorption isotherm equations. The accepted mechanism of biosorption may, however, influence strongly the differences between the initial and equilibrium states of biosorption system.     

Kinetics and equilibrium studies of adsorption of chromium(VI) ion from industrial wastewater using Chrysophyllum albidum (Sapotaceae) seed shells

A new biosorbent has been prepared by coating Chrysophyllum albidum (Sapotaceae) seed shells with chitosan and/or oxidizing agents such as sulfuric acid. This study investigated the technical feasibility of activated and modified activated C. albidum seed shells carbons for the adsorption of chromium(VI) from aqueous solution. The sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration and particle size on adsorption was also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The pseudo-first-order rate equation by Lagergren and pseudo-second-order rate equation were tested on the kinetic data, the adsorption process followed pseudo-second-order rate kinetics, also, isotherm data was analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms, the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 84.31, 76.23 and 59.63 mg Cr(VI)/g at initial pH of 3.0 at 30 °C for the particle size of 1.00–1.25 mm with the use of 12.5, 16.5 and 2.1 g/L of CACASC, CCASC and ACASC adsorbent mass, respectively. This readily available adsorbent is efficient in the uptake of Cr(VI) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater.     

Removal of chromium from water using pea waste – a green approach

Abstract

Agro-waste materials have carboxylic and phenolic groups that play the main role in metal adsorption. The advantages of these materials include easy availability, low cost, and reasonable metal removal capacity. One of the materials (usually considered as waste) is pea waste (pods). Present work comprises adsorption of chromium from aqueous solution using powder of pods of garden peas (Pisum sativum) in batch. Important parameters like adsorbent dose, pH, contact time, and agitation speed were studied. Adsorption equilibrium was explained by Langmuir, Freundlich, and Temkin isotherms. Maximum chromium uptake (q _m) was 3.56 mg/g of adsorbent. Heat of adsorption, as evaluated by Temkin isotherm was 1.96 kJ/mol. It is proposed that pea pods can be an effective and environmentally benign (green) adsorbents for removal of chromium from industrial effluents and waste waters.     

Equilibrium and kinetic studies of adsorption of phosphate onto ZnCl2 activated coir pith carbon

Phosphate removal from aqueous solution was investigated using ZnCl₂-activated carbon developed from coir pith, an agricultural solid waste. Studies were conducted to delineate the effect of contact time, adsorbent dose, phosphate concentration, pH, and temperature. The adsorption equilibrium data followed both Langmuir and Freundlich isotherms. Langmuir adsorption capacity was found to be 5.1 mg/g. Adsorption followed second-order kinetics. The removal was maximum in the pH range 3–10. pH effect and desorption studies showed that adsorption occurred by both ion exchange and chemisorption mechanisms. Adsorption was found to be spontaneous and endothermic. Effect of foreign ions on adsorption shows that perchlorate, sulfate, and selenite decreased the percent removal of phosphate.