藻蓝蛋白静态吸附平衡及热力学研究

研究了钝顶螺旋藻中藻蓝蛋白在DEAE-Sephadex A-50离子交换树脂上的静态吸附平衡,考察了无机盐NaCl浓度和聚合物PEG6000质量分数,以及吸附温度对藻蓝蛋白静态吸附平衡的影响,以Langmuir和Freundlich吸附等温方程分别对不同条件下的吸附平衡数据进行拟合,并计算出吸附过程的热力学参数△G,△...     

Palladium,silver, and zinc oxide nanoparticles loaded on activated carbon as adsorbent for removal of bromophenol red from aqueous solution

The adsorption of bromophenol red (BPR) onto three adsorbents including palladium, silver and zinc oxide nanoparticles loaded on activated carbon (Pd-NP-AC, Ag-NP-AC and ZnO-NP-AC) in a batch system has been studied and the influence of various parameters has been optimized. The influence of time on removal of BPR on all adsorbent was investigated and experimental data were analyzed by four kinetic models including pseudo first and second-order, Elovich and the intraparticle diffusion equations. Following fitting the experimental data to these models, the respective parameters of each model such as rate constants, equilibrium adsorption capacities and correlation coefficients for each model were investigated and based on well known criterion their applicability was judged. It was seen that the adsorption of BPR onto all adsorbents sufficiently described by the pseudo second-order equation in addition to interparticle diffusion model. The adsorption of BPR on all adsorbent was investigated at various concentration of dye and the experimental equilibrium data were analyzed and fitted to the Langmuir, Freundlich, Tempkin, Dubinin, and Radushkevich equations. A single stage in batch process was efficient and suitable for all adsorbents using the Langmuir isotherm with maximum adsorption of 143 mg g^?1 for Pd-NP-AC, 250 mg g^?1 for Ag-NP-AC and 200 mg g^?1 for ZnO-NR-AC. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° for Pd-NP-AC adsorbent were calculated.     

Equilibrium and Thermodynamic Studies on the Removal and Recovery of Safranine-T Dye from Industrial Effluents

In this study, deoiled-mustard obtained from local oil mills has been used as an inexpensive and effective adsorbent for the removal of Safranine-T dye from wastewater. The influence of various factors on the adsorption capacity has been studied by batch experiments. The adsorption studies revealed that the ongoing adsorption validates Langmuir adsorption isotherms better than the Freundlich adsorption isotherm at temperatures 40, 50, 60°C. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° for the adsorption process were calculated. Desorption profile revealed that a significant portion (83%) of the dye could be desorbed by using 12% acetic acid solution as an eluting agent. A comparative analysis of the adsorption capacities of various adsorbents reveals the superior performance of the adsorbent under study. The results indicated that deoiled-mustard is a good and low-cost adsorbent from the practical point of view for dyes removal and can be used as an economically viable alternative to commercial activated carbon.     

Removal of Cr(VI) From Aqueous Solution by Turkish Vermiculite: Equilibrium,Thermodynamic and Kinetic Studies

Abstract

The adsorption of Cr(VI) from aqueous solution by Turkish vermiculite were investigated in terms of equilibrium, kinetics, and thermodynamics. Experimental parameters affecting the removal process such as pH of solution, adsorbent dosage, contact time, and temperature were studied. Equilibrium adsorption data were evaluated by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Langmuir model fitted the equilibrium data better than the Freundlich model. The monolayer adsorption capacity of Turkish vermiculite for Cr(VI) was found to be 87.7 mg/g at pH 1.5, 10 g/L adsorbent dosage and 20°C. The mean free energy of adsorption (5.9 kJ/mol) obtained from the D–R isotherm indicated that the type of sorption was essentially physical. The calculated thermodynamic parameters (ΔG ^o , ΔH ^o and ΔS ^o ) showed that the removal of Cr(VI) ions from aqueous solution by the vermiculite was feasible, spontaneous and exothermic at 20–50°C. Equilibrium data were also tested using the adsorption kinetic models and the results showed that the adsorption processes of Cr(VI) onto Turkish vermiculite followed well pseudo-second order kinetics.     

Removal of Sr(II) from Aqueous Solutions by Aminosilane Functionalized MCM-48

In this research, NH₂-MCM-48 adsorbent was synthesized by grafting of aminopropyl on the surface of MCM-48 mesoporous silica material. The synthesized adsorbent was characterized by FT-IR, XRD, thermogravimetric, and surface area techniques. The removal of Sr (II) by the synthesized adsorbent was studied and the effect of initial pH, contact time, cation concentration, and temperature on the Sr²⁺ adsorption was studied and optimized. Under optimized conditions, the removal capacity of 5.95 meq/g was obtained. The experimental data were analyzed using the Langmuir and Freundlich equations. Adsorption data was fitted with the Langmuir isotherm, indicating that the process was monolayer and chemical in nature. The calculated thermodynamic parameters, ΔH°, ΔS°, and ΔG° confirmed that the adsorption process was endothermic and spontaneous. The regeneration of the adsorbent was examined and it was found that 92% of the initial capacity was conserved after five successive regeneration cycles.     

A comparative study of removal of Cu(II) from aqueous solutions by locally low-cost materials: marine macroalgae and agricultural by-products

In this study, adsorption of Cu(II) onto the five locally abundantly low-cost biosorbents (Laminaria japonica, P. yezoensis Ueda, rice bran, wheat bran and walnut hull) was investigated depending on initial solution pH, contact time, adsorbent concentration and reaction temperature. Cu(II) removal was pH-dependent for various biosorbents investigated. For P. yezoensis Ueda, rice bran, wheat bran and walnut hull, the batch equilibrium data were correlated to Langmuir and Freundlich isotherms and the data fitted better to the Langmuir isotherm equation and yielded Langmuir monolayer capacity of 5.04, 10.41, 6.85 and 3.52 mg/g at the temperature of 20°C, respectively. In the case of Laminaria japonica, the equilibrium data obeyed the Hill-der Boer equation for the whole initial concentration ranges of 0–200 mg/L examined, but only to Langmuir and Freundlich equations for the initial concentration less than 120 mg/L at various temperatures. The apparent thermodynamic parameters were calculated for each of the five biosorbents (ΔH = 9.25–40.04 kJ/mol; ΔG = –17.60 to –24.16 kJ/mol and ΔS = 85.81–228 J/mol K). The numerical values obtained showed that Cu(II) adsorption is a spontaneous, entropy-driven and endothermic process. The batch kinetic data were correlated to the pseudo-first order and pseudo-second order models and the data fitted better to the pseudo-second order equation (the pseudo-second order rate constants, k_2,e = 0.1059–0.9453 g/(mg min); the correlation coefficients, r = 0.9816–0.9993).     

Coconut (Cocos nucifera) Shell Based Activated Carbon for the Removal of Malachite Green Dye from Aqueous Solutions

The adsorption of malachite green (MG) dye using coconut shell based activated carbon (CSAC) was investigated. Operational factors such as the effect of pH, initial dye concentration, adsorbent dosage, contact time, and solution temperature on the adsorption process were studied. Solution pH strongly affected the chemistry of both the dye molecule and CSAC in solution. Optimum dye removal was obtained at pH ≥ 8.0. Equilibrium was reached in 120 minutes contact time. The Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models were used to evaluate the adsorption data. The adsorption data fitted the Langmuir model most with maximum adsorption monolayer coverage of 214.63 mg/g. Pseudo-first-order, pseudo second-order, and intraparticle diffusion models were also used to fit the experimental data. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients, for each model were calculated and discussed. Thermodynamic parameters such as ΔG⁰, ΔH⁰, and ΔS⁰ were evaluated and it was found that the sorption process was feasible, spontaneous, and exothermic in nature. The mean free energy obtained from D-R isotherm suggests that the adsorption process follows physiosorption mechanism. The results showed that coconut shells could be employed as a low-cost precursor in activated carbon preparation for the removal of MG dye from wastewaters.     

Removal of Pb(II) from aqueous solution by adsorption using activated tea waste

A basic investigation on the removal of Pb(II) ions from aqueous solutions by using activated tea waste was conducted in batch conditions. An inexpensive and effective adsorbent was developed from waste tea leaves for the uptake of Pb(II) from aqueous solution. The influence of different experimental parameters—shaking time, particle size, adsorbent dose, initial pH, temperature, etc.—on lead uptake was evaluated. Lead is adsorbed by the developed adsorbent up to maximum of 99.7%. The initial Pb(II) concentrations were 5, 10, 15 and 20 mg/l in the experiment. The adsorption was found to be exothermic in nature. The Langmuir, Freundlich and Tempkin isotherm models were tried to represent the equilibrium data of Pb(II) adsorption. The adsorption data was fitted very well to the Langmuir isotherm model in the studied concentration range of Pb(II) adsorption. Isotherms have been used to determine thermodynamic parameters of the process: free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°). Column experiments were performed to study the practical applicability of the system. The kinetics and the factors controlling the adsorption process were also discussed. Activated tea waste is a better adsorbent compared to other adsorbents available in literature.     

Removal of Selected Basic Dyes using Activated Carbon from Tannery Wastes

Activated carbon prepared from tannery leather waste (TLW-AC) has been studied for its efficiency of removal of basic dyes, namely rhodamine B (RB), methylene blue (MB), and malachite green (MG) from aqueous solutions. Factors influencing dye adsorption such as the concentration of dye, pH, contact time, and temperature were investigated. The adsorption was found to be strongly dependent on the pH and temperature. The maximum sorption capacity of RB was obtained at pH 3 and for MB and MG was obtained at pH 11. Various thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated. The kinetic studies reveal that the adsorption process follows the pseudo second-order kinetic model. The equilibrium data have been well-described by the Langmuir and Freundlich models, and the data fitted well in both model equations. The study revealed that wastes from leather industry is an economically viable option for dye removal.     

活性炭纤维对Cu2+的吸附性能研究

活性炭纤维(ACF)作为一种新型活性炭吸附材料已引起了化学家们的极大关注。孔结构分析表明:活性炭纤维的孔径分布窄,孔径比较均匀。本文以活性炭纤维作为去除水中重金属离子Cu2+的吸附剂,吸附实验表明,活性炭纤维对Cu2+的最大吸附量为148.50mg.g-1,吸附平衡时间短,当接触时间为50min时,即可达到吸附平衡,吸附过程符合Langmuir和Freundlich模型。动态吸附结果表明,活性炭纤维对Cu2+的吸附量随着流速的增加而降低。     

Comparison of Basic Dye Crystal Violet Removal from Aqueous Solution by Low-Cost Biosorbents

Abstract

The removal of basic dye crystal violet by low-cost biosorbents was investigated in this study using a batch experimental system. The adsorption of crystal violet onto various adsorbents was solution pH-dependent and the maximum removal occurred at basic pH 10.0. The kinetic experimental data were analyzed using pseudo-first-order and pseudo-second-order equations to examine the adsorption mechanism and the intraparticle diffusion model to identify the potential rate controlling step. These results suggested that the adsorption of crystal violet onto various adsorbents was best represented by the pseudo-second-order equation. The suitability of the Langmuir and Freundich adsorption isotherms to the equilibrium data was also investigated at various temperatures for all four sorbents and the adsorption isotherms exhibited Freundlich behavior. The Freundlich constant K_f was 1.55 for alligator weed, 2.33 for Laminaria japonica, 9.59 for rice bran and 5.38 (mg/g)/(mg/L)^1/n for wheat bran, respectively at adsorbent concentration 5 g/L, pH 10.0 and 20°C. The thermodynamic parameters (ΔH, ΔG, and ΔS) were calculated and the results showed that the adsorption process for various adsorbents was spontaneous, endothermic, with an increased randomness, respectively. The particle size and the reaction temperature exhibited an insignificant impact on the adsorption equilibrium of crystal violet. The adsorbents investigated could serve as low-cost adsorbents for removing the crystal violet from aqueous solution.     

Application of flyash instead of activated carbon for oxalic acid removal

Flyash, a waste product from thermal power plants, has been used as an adsorbent for the removal of oxalic acid. The adsorption process follows first-order kinetics and the equilibrium is attained within 30 min in the concentration range studied (0.01-0.1M). The adsorption obeys both the Freundlich and Langmuir isotherms and the constants have also been reported for flyash and activated carbon. At low concentrations, the increase in pH with flyash is comparatively more than for activated carbon. There seems to be a good scope for the use of flyash in place of activated carbon as an adsorbent for oxalic acid removal.     

Removal of copper from industrial wastewaters by activated carbon prepared from periwinkle shells

The present study aims at the removal of copper from industrial wastewater by using a low-cost adsorbent. Activated periwinkle shell carbon (PSC) was prepared and characterized for various physiochemical properties. To determine copper removal capacity, the performance of PSC was compared with commercial activated carbon (CAC) and a mixture of activated periwinkle shell carbon and commercial activated carbon (PSC:CAC) in a ratio 1:1. The effect of adsorbent dose, contact time, pH, agitation speed and adsorbent particle size was studied for adsorption of copper from wastewater under batch conditions. The result obtained showed that PSC competes favourably with CAC. The maximum adsorption capacity was observed for PSC:CAC with 88.12% removal at an optimal pH of 8. The PSC and CAC had 84.19% removal and 85.15% removal, respectively. The equilibrium data obtained fitted both the Langmuir and the Freundlich models. Good correlation coefficients were obtained for the pseudo-second-order kinetic model.     

Adsorptive removal of cationic dye from aqueous solutions by ZnO/ZnMn2O4 nanocomposite

The ZnO/ZnMn₂O₄ nanocomposite (ZnMn) was used as adsorbent for the removal of cationic dye Basic Yellow 28 (BY28) from aqueous solutions. The adsorbent was characterized by X-ray diffraction, scanning electron microscope, TEM, Fourier transform infrared ray, BET, particle size distribution and zeta potential measurements. The adsorption parameters, such as temperature, pH and initial dye concentration, were studied. Kinetic adsorption data were analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The Langmuir and Freundlich isotherm models were applied to fit the equilibrium data. The maximum adsorption capacity of BY28 was 48.8 mg g^?1. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were calculated.     

Adsorption ability of oxidized multiwalled carbon nanotubes towards aqueous Ce(III) and Sm(III)

The aim of the present work was to investigate the adsorption of Ce(III) and Sm(III) onto multiwalled carbon nanotubes (MWCNTs) oxidized with concentrate nitric acid. The effects of solution pH, adsorbent dosage, and contact time were studied by batch technique. Langmuir, Freundlich and D-R isotherms were used to describe the adsorption behavior of Ce(III) and Sm(III) by oxidized MWCNTs, and the experimental results fitted Freundlich model well. The maximum uptake capacities (q _m ) calculated by applying the Langmuir equation for samarium and cerium ions were found to be 89.28 and 92.59 (mg/g), respectively. A comparison of the kinetic models and the overall experimental data was best fitted by the pseudo second-order kinetic model. The calculated thermodynamic parameters (ΔG^o, ΔH^o, and ΔS^o) showed that the adsorption for Ce(III) and Sm(III) is feasible, spontaneous and exothermic at 30–60 °C. Moreover, more than 70% of Ce(III) and Sm(III) adsorbed onto Oxidized MWCNTs could be desorbed with HNO₃.     

Competitive adsorption of Direct Yellow 12 and Reactive Orange 12 on ZnS:Mn nanoparticles loaded on activated carbon as novel adsorbent

A novel adsorbent (ZnS:Mn nanoparticles loaded on activated carbon) was made. The competitive adsorption of Direct Yellow 12 (DY12) and Reactive Orange 12 (RO12) dyes in binary mixture onto this adsorbent was studied. DY12 and RO12 with severe spectra overlapping were chosen and analyzed simultaneously with high accuracy by first order derivative spectrophotometric method in binary solutions. The effect of multi-solute systems on the adsorption capacity was investigated. Because of the specific characteristics of ZnS:Mn-NP-AC was found to be efficient for the removal of the dyes studied. The adsorption capacities were investigated and described by the mono- and multi-component Langmuir and Freundlich isotherm models for both single and binary dye solutions. The isotherm constants for DY12 and RO12 were calculated. For single solution of DY12 and RO12 dyes, the adsorption capacities of the applied adsorbent were found to be 90.05 mg/g and 94.52 mg/g, respectively. Equilibrium uptake amounts of DY12 and RO12 in binary solution onto the applied adsorbent were found to be considerably decreasing with increasing the concentrations of the other dye. A better agreement between the adsorption equilibrium data and mono-component Langmuir isotherm model was found. However, at concentrations within moderate ranges, the extended Freundlich isotherm model satisfactorily predicted multi-component adsorption equilibrium data. An endothermic and a spontaneous nature for the adsorption of the dyes studied were shown from thermodynamic parameters.     

Anthracene removal from water onto activated carbon derived from vehicular tyre

The present study focuses on adsorptive removal of anthracene by application of activated carbon developed from waste vehicular tyres (VTAC). Different experimental parameters were varied to examine their influence on anthracene adsorption. The results reveal that concentration of anthracene in aqueous phase reduces continuously with enhancement in shaking time. After a period of 75 min, the adsorption of anthracene on VTAC was observed to be in equilibrium. The adsorption of anthracene was >99% in presence of 14–20 mg and an adsorbent dose of 8 mg was used to analyse the effect of other parameters in the present study. As pH of solution is lowered, rise in adsorption capacity of VTAC was observed. The obtained data were applied to Langmuir and Freundlich isotherms for studied PAH adsorption. The second order kinetics was suggested to be better fitted with R² values >0.95. Intra-particle diffusion and Boyd-Reichenberg model were applied for investigating the mechanism of adsorption.     

Adsorption Characteristics of Sulfamethoxazole and Metronidazole on Activated Carbon

In this work, the removal of two pharmaceuticals i.e., an antibiotic drug, sulfamethoxazole and an antiparasitary drug, metronidazole onto activated carbon from aqueous solutions were studied. Batch adsorption studies were carried out at different pH, adsorbent concentrations, and temperatures. Adsorption isotherms have been modeled by Freundlich, Langmuir, and Dubinin-Raduskevitch (D-R) equations. The adsorption of these drugs was better represented by the Langmuir equation. The effect of the solution pH on the adsorbed amount of SM and MN was studied by varying the initial pH under constant process parameters at equilibrium conditions. The increase in pH of the solutions caused to decrease adsorption of SM and MN on AC. The kinetics of adsorption in view of three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model was discussed. The pseudo-second-order kinetic model describes the adsorption of both sulfamethoxazole and metronidazole on activated carbon. Rate constants for adsorption and desorption, and surface coverage have been evaluated with the help of another approach of the kinetic scheme. The effect of temperature was also studied at the range between 293 and 313 K. Thermodynamic parameters were calculated. The negative value of enthalpy change (ΔH°) indicated the exothermic nature of the adsorption process, and the negative values of free energy change (ΔG°) were indicative of spontaneity of the adsorption process. In this work adsorption behaviour of SM and MN on activated carbon was also evaluated by the data obtained from column experiments.     

Isotherms,kinetics, and thermodynamic studies for adsorption of pigments and oxidation products in oil bleaching from catfish waste

Abstract

The aim of this work was to study the bleaching of oil extracted from the heads of the catfish by thermomechanical process through equilibrium, kinetics, and thermodynamics adsorption studies. The condition for the bleaching step was with 1% (w/w) adsorbent composed of 95% activated earth and 5% activated carbon (w/w). The pseudo-first order and pseudo-second order models were the most appropriate to represent the adsorption kinetics. The temperature of 80?°C increased the adsorption capacity of the two adsorbates, and the activation energies values were of 47.47 and 44.82?kJ mol^?1, respectively, for the adsorption of carotenoids and peroxides. The Langmuir model was the most appropriate to describe the bleaching equilibrium curves. The thermodynamic parameters revealed that the processes were endothermic, favorable, and spontaneous and the interaction between adsorbent and adsorbate was physical.