Chnoong Kheng Lee

Removal of Cu and Pb by tartaric acid modified rice husk from aqueous solutions

A study on the modification of rice husk by various carboxylic acids showed that tartaric acid modified rice husk (TARH) had the highest binding capacities for Cu and Pb. The carboxyl groups on the surface of the modified rice husk were primarily responsible for the sorption of metal ions. A series of batch experiments using TARH as the sorbent for the removal of Cu and Pb showed that the sorption process was pH dependent, rapid and exothermic. The sorption process conformed to the Langmuir isotherm with maximum sorption capacities of 29 and 108 mg/g at 27 +/- 2 degrees C for Cu and Pb, respectively. The uptake increased with agitation rate. Decrease in sorbent particle size led to an increase in the sorption of metal ions and this could be explained by an increase in surface area and hence binding sites. Metal uptake was reduced in the presence of competitive cations and chelators. The affinity of TARH for Pb is greater than Cu.

SORPTION OF CADMIUM AND LEAD FROM AQUEOUS SOLUTIONS BY SPENT GRAIN

The sorption of cadmium and lead from aqueous solutions by spent grain, a by-product of the brewing process, was investigated. The effects of solution pH, ionic strength, initial concentration, ligands and temperature were studied in batch experiments. The equilibrium process was described well by the Langmuir isotherm model with maximum sorption capacities of 17.3 and 35.5 mg/g of cadmium and lead on spent grain, respectively. The enthalpy of sorption was endothermic and the increase in Pb uptake was larger than that of Cd over the same rise in temperature. The initial uptake was rapid and equilibrium was established in less than 120 min. Good correlation coefficients were obtained for the pseudo second-order kinetic model. Equimolar concentrations of Cd and Pb to ethylenediamine tetraacetic acid and nitrilotriacetic acid almost completely suppressed the uptake of metals. Sorption capacities of spent grain for cadmium and lead were compared with some low-cost biological materials.

QUATERNIZED RICE HUSK AS SORBENT FOR REACTIVE DYES

A study on the sorption of hydrolyzed Reactive Blue 2 by quaternized rice husk showed that the binding capacity of the sorbent was not suppressed by dyebath conditions of high concentration of electrolytes. Its sorption capacity decreased with increasing concentration of NaOH. Complete regeneration of dye-coated quaternized rice husk was not possible under base treatment, suggesting chemisorption of dye molecules on the sorbent material. The physical stability of the quaternized rice husk was examined by treating it with various concentrations of NaOH solution. Results showed that no dissolution of sorbent occurred, even in 1 M NaOH solution.

Removal of Cu and Pb from electroplating wastewater using tartaric acid modified rice husk

The potential of using tartaric acid modified rice husk (TARH) as a sorbent for the removal of Cu and Pb from semiconductor electroplating wastewater was investigated. Application of Langmuir isotherm indicated that there was no difference in the sorption capacity of TARH for Cu and Pb in synthetic solution and wastewater. A series of column studies were carried out. Increase in column bed depth yielded longer service time while increase in influent concentration and flow rate resulted in faster breakthrough. The sorption capacities of the TARH column for Cu and Pb agreed closely with the levels obtained from batch equilibrium studies. Theoretical breakthrough curves at different bed heights and flow rates generated using a two-parameter model agreed closely with experimental values in the treatment of semiconductor wastewater. In the regeneration study, Cu and Pb could be recovered almost quantitatively by eluting the column with 0.1 M HCl and the column could be used repeatedly for at least five cycles.

Stoichiometry and stability of bismuth vanadate, Bi4V2O11, solid solutions

The phase reported in the literature as Bi4V2O11 is a solid solution phase whose composition covers the range ∼66.7 to 70.4% Bi2O3. The phase diagram of the Bi2O3V2O5 system in the region of this phase has been determined and electrical properties of the Bi4V2O11 solid solutions measured. The high temperature γ polymorph is an excellent oxide ion conductor, whose conductivity decreases gradually with increasing Bi2O3 content. The low temperature α polymorph is a ferroelectric whose permittivity appears to increase to a maximum at the α→β transition temperature.

Column study on the sorption of Cr(VI) using quaternized rice hulls

The potential of quaternized rice hulls in removing Cr(VI) from synthetic solution, chrome electroplating waste and wood preservative waste was investigated in column experiments. Increase in column bed depth resulted in a longer service time at CtCo = 0.5 breakthrough. The presence of SO2−4, which is commonly present in the wastes, interfered with the sorption process and resulted in earlier breakthrough. The sorption process was flow-rate independent within the scope of this study. In the regeneration study, Cr(VI) could be recovered almost quantitatively by eluting with a 0.5 M NaOH solution and the column could be used repeatedly for at least five cycles.

Quaternized wood as sorbent for reactive dyes.

Various species of local wood modified with N-(3-chloro-2-hydroxypropyl)-trimethylammonium chloride showed sorption enhancement for hydrolyzed Reactive Blue 2 (HRB) compared to the untreated samples. The enthalpy of sorption of HRB on Simpoh (Dillenia suffruticosa) was found to be endothermic. Maximum sorption capacity calculated from the Langmuir isotherm was 250.0 mg/g. Under continuous flow conditions HRB could be successfully removed. Dye removal was a function of bed depth and flow rate. However, the bed depth service time model of Bohart and Adams was not applicable in the HRB-quaternized wood system. The modified wood was applied to a sample of industrial textile effluent, and it was found to be able to remove the color successfully under batch conditions.

Sorption of Cr(VI) and Cu(II) in aqueous solution by ethylenediamine modified rce hull

Abstract The sorption characteristics of Cr(VI) and Cu(II) by ethylenediamine modified rice hull from single and binary metal ion solutions were evaluated under various experimental conditions. Optimal Cr(VI) and Cu(II) removal from single metal ion solutions occurred at pH 2.0 and 5.5, respectively. Simultaneous removal of Cr(VI) and Cu(II) occurred at pH greater than 3.0. The sorption kinetics of Cr(VI) and Cu(II) from single and binary metal ion solutions were studied with reference to metal concentration, agitation rate and particle size. Sorption of Cr(VI) was more rapid than Cu(II). The kinetics of metal ion sorption fitted a pseudo‐second order expression. The variation in the initial uptake rates was very small at an agitation rate beyond 150 rpm and sorption was generally independent of particle size. Equilibrium sorption data could be fitted into the Langmuir isotherm equation. Maximum sorption capacities of ethylenediamine modified rice hull for Cr(VI) at pH 2 and Cu(II) at pH 4 in single metal solutions were 0.45 and 0.06 mmol g−1, respectively. This corresponds to an enhancement factor of 2.6 and 3 fold for Cr(VI) and Cu(II), respectively, compared to natural rice hull. A synergistic effect was observed for sorption of these ions in binary metal solutions.

Removal of some organic dyes by hexane-extracted spent bleaching earth

The removal of some organic dyes from aqueous solution by hexane-extracted spent bleaching earth, a waste material from the palm oil industry, was investigated. It was noted that the material had better affinity for basic than acid dyes. Various parameters affecting the removal process were studied. These were pH, initial dye concentration, sorbent dosage, temperature and agitation rate in the batch process. Experimental data show that both the boundary layer and intraparticle diffusion effect play important roles in the rate of dye removal. Maximum sorption capacities for some basic and acid dyes studied compare favourably with those reported using other low-cost sorbents.

Removal of Arsenic(V) from Aqueous Solution by Quaternized Rice Husk

The potential of using quaternized rice husk (QRH) as a sorbent for the removal of As(V) from aqueous solution was investigated. Both batch and column studies were carried out. Results of batch studies indicate that sorption was pH and temperature dependent. Equilibrium was attained within 20 minutes and sorption appeared to be essentially an ion exchange process. Experimental data could be fitted into the Langmuir isotherm with a maximum sorption capacity of 18.98 mg g−1 at pH 7.5 and 28±2°C. Anions such as SO4 2− and CrO4 2− interfere with the uptake of As(V) by QRH. In the column studies, results show that breakthrough depends on bed depth but not on flow rate as sorption was very rapid. In addition, service time at 50% breakthrough was inversely proportional to influent concentration and had a linear relationship with bed-depth.