Weihua Zou

Characterization of modified sawdust, kinetic and equilibrium study about methylene blue adsorption in batch mode

Methylene blue (MB) biosorption by citric acid modified pine sawdust (Pinus tabulaeformis) was studied from aqueous solutions. Batch experiments were conducted to determine the biosorption properties of the biomass. The Langmuir isotherm equation could fit the equilibrium data. The maximal equilibrium quantity of MB from Langmuir model was 111.46 mg g−1 at 293 K. The Elovich model adequately described the kinetic data in comparison to the pseudo-first-order model and pseudo-second-order model; the process involving rate-controlling step is very complex involving both boundary layer and intra-particle diffusion processes. The effective diffusion parameter Di and Df values were estimated at different initial concentration, and the average values were determined to be 5.76×10−8 and 2.12× 10−7 cm2 s−1. Thermodynamic parameters showed that the adsorption of methylene blue onto pine sawdust biomass was feasible, spontaneous and endothermic under studied conditions. The physical and chemical properties of the biosorbent were determined by SEM, TG-DSC, XRD, and the point of zero charge (pHpzc) and the nature of biomass-dye interactions were evaluated by FTIR analysis, which showed the participation of COOH, OH and NH2 groups in the biosorption process. Biosorbents could be regenerated using 0.01 mol L−1 HCl solution at least three cycles, with up to 90% recovery. Thus, the biomass used in this work proved to be effective for the treatment of MB bearing aqueous solutions.

Investigation of synergistic adsorption between methyl orange and Cd(II) from binary mixtures on magnesium hydroxide modified clinoptilolite

The simultaneous removal of Methyl orange (MO) and Cd2+ (mainly from organo-metallic dyes) onto magnesium hydroxide modified clinoptilolite (MHMC) was described and compared to a single adsorbate situation. The adsorption performance was studied by batch experiments. The adsorption mechanism of MO and Cd2+ on MHMC was investigated. Langmuir and Dubinin-Raduskevich (D-R) isotherm successfully predicted the adsorption of MO and Cd2+ in single and binary systems. Maximum adsorption capacity calculated from Langmuir isotherm equation in single solution for MO and Cd2+ was 0.305 and 0.282mmol/g, respectively. In a binary system of MO/Cd2+, the adsorption capacity for both MO and Cd2+ was higher than in single solutions. The results indicated that the adsorption system of MO/Cd2+ presented a synergistic effect, not competitive adsorption, which suggested that MHMC can be used as an adsorbent for removal of dyes and heavy metal in the multi-solute system.

Investigations on the batch performance of cationic dyes adsorption by citric acid modified peanut husk

Abstract A citric acid modified peanut husk (MPH) was used as adsorbent for removal of neutral red (NR) and methylene blue (MB) from aqueous solution. A batch system was applied to study the behavior of NR and MB adsorption in single and binary systems on MPH. Such studies were conducted by varying various parameters such as the initial dye concentration, the pH, the salt concentration, the temperature, and the contact time. Adsorption kinetic data were fitted using pseudo-first-order equation, pseudo-second-order equation, and intraparticle diffusion model. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter D i values estimated in the order of 10−8 cm2/s indicated that the intraparticle diffusion was not the rate-controlling step. The NR adsorption isotherm follows the Langmuir model, while MB adsorption follows the Freundlich isotherm. The thermodynamics parameters of adsorption systems indicated spontaneous and endo...

Use of Oxalic Acid-modified Rice Husk for the Adsorption of Neutral Red from Aqueous Solutions

Rice husk modified with oxalic acid (MRH) was tested as a lowcost adsorbent for the removal of Neutral Red (NR) dye from aqueous solutions employing batch adsorption procedures. Such studies were conducted by varying various parameters such as the pH, the adsorbent dosage, the salt concentration, the contact time, the concentration of the adsorbate and the temperature. The kinetic experimental data were analyzed using three kinetic equations, viz. the pseudo-first-order equation, the pseudo-second-order equation and the intra-particle diffusion model equation, to examine the mechanism of adsorption and the potential rate-controlling step. The mechanism of the process was found to be complex, consisting of both surface adsorption and pore diffusion. The values of the effective diffusion parameter, Deff, were estimated to be of the order of 10−8 cm2/s, indicated that intra-particle diffusion was not the rate-controlling step. The equilibrium adsorption data obtained at various temperatures were analyzed using the Langmuir, Freundlich and Redlich–Peterson isotherm models using non-linear regressive analysis. The equilibrium adsorption results were better fitted by the Langmuir and Redlich–Peterson isotherms relative to the Freundlich model. Calculated thermodynamic parameters showed that the adsorption of NR onto MRH was feasible, spontaneous and endothermic under the studied conditions. The carboxyl groups on the surface of the modified rice husk (MRH) were primarily responsible for the sorption of NR. It is suggested that MRH may be suitable as an adsorbent material for adsorbing NR from aqueous solutions.

Use of Manganese Oxide-Coated Sand for the Adsorption of Uranium(VI) Ions from Aqueous Solution Using a Column Mode

Continuous fixed-bed studies were undertaken to evaluate the performance of manganese oxide-coated sand (MOCS) as an adsorbent for the removal of uranium(VI) ions from aqueous solution under the effect of various process parameters such as the bed depth, the flow rate, the presence of salt and the initial U(VI) ion concentration. The U(VI) ion uptake by MOCS increased with initial U(VI) ion concentration and bed height, but decreased as the flow rate increased. A shorter breakthrough time was observed in the presence of salt. The experimental data obtained from the breakthrough curves were analyzed using the Thomas model. The BDST model was also applied to predict the service times for other flow rates and initial concentrations. The results showed that the Thomas model was suitable for the description of the whole breakthrough curve, while the data were in good agreement with the BDST model. The columns were regenerated by eluting the bound U(VI) ions with 0.5 mol/ℓ HNO3 solution after the adsorption studies. MOCS could be re-used to adsorb U(VI) ions at a comparable capacity. Compared to virgin sand, the removal of U(VI) ions from MOCS proceeded more readily.

Characterization of Manganese Oxide and the Adsorption of Copper(II) and Lead(II) Ions from Aqueous Solutions

The characterization and sorption properties of manganese oxide towards Cu(II) and Pb(II) ions from aqueous solution were investigated. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared (IR) analyses were used to characterize the manganese oxide. Parameters affecting the adsorption of Cu(II) and Pb(II) ions, such as the adsorbent dosage, the ionic strength of the solution, the contact time, the solution pH, the initial metal ion concentration and the temperature, were investigated. The binding of Cu(II) and Pb(II) ions to manganese oxide was highly dependent on the pH of the solution, with the extent of adsorption increasing as the pH of the system increased. The uptake of both Cu(II) and Pb(II) ions was found to increase with temperature. Furthermore, the removal efficiency of Cu(II) and Pb(II) ions from aqueous solution increased with increasing adsorbent dosage and decreased with ionic strength. The adsorption equilibrium and adsorption kinetics of Cu(II) and Pb(II) ions onto manganese oxide were studied. The adsorption process was spontaneous and exothermic, with the order of affinity being Pb(II) > Cu(II). The same behaviour was observed during competitive adsorption, viz. adsorption from a binary solution of the ions concerned.

A Novel Pinus Tabulaeformis Based Adsorbent for the Removal of Malachite Green

Pyrolytic char treated with muffle furnace (TPC), a novel adsorbent, were investigated to enhance its adsorption capacity of malachite green (MG) dye. In addition, the dye adsorption behavior of the TPC in aqueous solution was investigated. The treatment temperature, treatment time, and the particle size of PC had a positive effect on the dye adsorption capacity of TPC. Equilibrium data was fitted well with Langmuir and Redlich-Peterson models with maximum adsorption capacity of 91.24, 111.27, and 119.01 mg g−1 at 293, 303, and 313 K, respectively. The kinetic of adsorption was found to confirm to the Elovich equation with good correlation and the overall rate of MG uptake was found to be controlled by film diffusion, pore diffusion and particle diffusion. The Boyd plot confirmed that the external mass transfer was the rate-limiting step in the adsorption process. Different thermodynamic parameters have also been evaluated and it was found that the adsorption was spontaneous, feasible, and endothermic in nature. Adsorbents could be regenerated using 0.1 mol L−1 NaOH solution at least three cycles, with up to 90% recovery. The TPC used in this work proved to be an effective material for the treatment of MG bearing aqueous solutions.