The solid phase preparation of a cationic sorbent, which bears hydroxyphosphates derived from esterified soybean hull, is reported. The sorption behaviors of Cu (II) and malachite green (MG) from aqueous solution onto modified soybean hull (MSH) were investigated in a batch system. The removal experiments were performed under various conditions such as different initial pH, MSH dosage, sorbate concentration and contact time. The maximum removal of Cu (II) and MG was obtained at initial solution pH≥3.0 and pH≥6.0, respectively. For 100 mg·L-1 of Cu solution, a removal ratio above 91% could be achieved by 5.0 g·L-1 or more of MSH. Above 95% of a 250 mg·L-1 MG dye solution could be removed by 2.0 g·L-1 or more of MSH. The sorption isotherms of both Cu (II) and MG fit the Langmuir model. The maximum removal capacity (Qm) of MSH was 31.55 mg·g-1 for Cu (II) and and 178.57 mg·g-1 for MG. The sorption equilibrium of Cu (II) was reached within 75 min and could be described by the pseudo-first-order kinetic model, while MG reached equilibrium after 7 h and fit pseudo-second-order kinetics.

One kind of potentially biodegradable cationic sorbent with high sorption capacity of basic dyes was prepared by thermochemically esterifying oxalic acid onto rice straw, and then the esterified rice straw was further loaded with sodium ion for enhancing its cationic sorption capacity. The sorption of two basic dyes, basic blue 9 (BB9) and basic green 4 (BG4), from aqueous solutions onto modified product was investigated. The effects of various experimental parameters (e.g. initial pH, sorbent dosage, dye concentration, ion strength, contact time) were examined and optimal experimental conditions were decided. The BB9 and BG4 removal ratios came up to the maximum value beyond pH 6. The 2.0 g/l or above of sorbent could almost completely remove BB9 and BG4 from 250 mg/l of dye solution. The ratios of BB9 and BG4 sorbed kept above 97% over a range from 50 to 250 mg/l of dye concentration when 2.0 g/l of sorbent was used. Increase in ion strength of solution induced decline of BB9 and BG4 sorption. The isothermal data fitted well to the Langmuir and Freundlich models. The sorption processes could be described by the pseudo-second-order kinetic model. The results in this research confirmed that the OA-modified rice straw was an excellent basic dye sorbent.

In this paper, rice straw was esterified thermochemically with citric acid (CA) to produce potentially biodegradable cationic sorbent. The modified rice straw (MRS) and crude rice straw (CRS) were evaluated for their methylene blue (MB) removal capacity from aqueous solution. The effects of various experimental parameters (e.g., initial pH, sorbent dose, dye concentration, ion strength, and contact time) were examined. The ratio of MB sorbed on CRS increased as the initial pH was increased from pH 2 to 10. For MRS, the MB removal ratio came up to the maximum value beyond pH 3. The 1.5g/l or up of MRS could almost completely remove the dye from 250mg/l of MB solution. The ratio of MB sorbed kept above 98% over a range from 50 to 450mg/l of MB concentration when 2.0g/l of MRS was used. Increase in ion strength of solution induced decline of MB sorption. The isothermal data fitted the Langmuir model. The sorption processes followed the pseudo-first-order rate kinetics. The intraparticle diffusion rate constant (kid) was greatly increased due to modification.

This paper reports the preparation of a phosphorylated cotton chelator (PCC) by solid phase esterification of phosphoric acid (PA) onto defatted cotton fibres using urea as the catalyst. The synthesized PCC was employed for the preconcentration of copper from water samples prior to its determination by flame atomic absorption spectrometry (FAAS). The preconcentration of copper was studied under both batch and column techniques. The pH range for the quantitative preconcentration of copper was 4.0-7.0. The sorption time required for each sample was less than 30 min by the batch method. The copper sorption capacity of the PCC was found to be 15.3 mg/g at the optimum pH value. Elution with 1.0 mol dm-3 hydrochloric acid was found to be quantitative. Feasible flow rates of the copper solution for quantitative sorption onto the column packed with PCC were 0.5-4.0 ml min-1, whereas the optimum flow rate of the hydrochloric acid solution for desorption was less than 1.5 ml min-1. An 80-fold preconcentration factor could be achieved under the optimum column conditions. The tolerance limits for common metal ions on the preconcentration of copper and the number of times of column reuse were investigated. The proposed method was successfully applied for the preconcentration and determination of trace copper in natural and drinking water samples by FAAS.

A cationic adsorbent with carboxyl groups derived from citric acid- esterified wheat straw (EWS) was prepared by the method of solid phase preparation, and a batch experiment was conducted to study the adsorption behaviors of Cu (II) and methylene blue (MB) in aqueous solution on the EWS under conditions of different initial pH, adsorbent dosage, adsorbate concentration, and contact time. The results showed that the maximum adsorption of Cu (II) and MB was obtained when the initial solution pH was > or = 4.0. 96% of Cu (II) in 100 mg x L(-1) Cu solution and 99% of MB in 250 mg x L(-1) dye solution could be removed by > or = 2.0 g x L(-1) of EWS. The adsorption of Cu (II) and MB fitted the Langmuir sorption isothermal model. The maximum removal capacity (Qm) of EWS was 79.37 mg x g(-1) for Cu (II) and 312.50 mg x g(-1) for MB, and the adsorption equilibrium of Cu (II) and MB was reached within 75 min and 5 h, respectively. The adsorption processes of Cu (II) and MB could be described by pseudo-first order and pseudo-second order kinetic functions, respectively.

In this paper, the solid phase preparation method of a cationic sorbent, which bears hydroxyl groups of phosphoric acid derived from esterified soybean hull (ESH), was reported. The sorption kinetics and thermodynamics of two basic dyes, acridine orange (AO) and malachite green (MG), from aqueous solution onto ESH were investigated with a batch system. The isothermal data of dye sorptions followed the Langmuir model better than the Freundlich model. The maximum sorption capacity (Q(m)) of ESH for AO and MG was 238.1 mg/g and 178.57 mg/g, respectively. The dye sorption processes could be described by the pseudo-second-order kinetic model. The thermodynamic study indicated that the dye sorptions were spontaneous and exothermic. Lower temperatures were favorable for the sorption processes.