[Coagulation performance and mechanism of Al(b) species in treating simulative dye wastewater].

Al(b) species was obtained from polyaluminum chloride (PAC) using ethanol-acetone mixed precipitation method. Al(b) and PAC were comparatively investigated in terms of color removal and zeta potential under different coagulant dosage and solution pH in the treatment of dispersive yellow and direct purple simulative dyeing wastewater. The changes of floc size of Al(b) and PAC were analyzed with PDA2000 and Mastersizer2000, and the coagulation mechanisms were also investigated. Compared with PAC, Al(b) species can work within a wider pH range and the flocs formed by Al(b) showed a more compact structure, a better settle ability and regrowth ability.

Characterization of floc size, strength and structure in various aluminum coagulants treatment.

Flocs generated in various aluminum coagulants treatment exhibit difference in size, strength and structure. The formation, breakage and re-formation of flocs were investigated by using a laser diffraction instrument (Malvern Mastersizer 2000, Malvern, UK). Different Al coagulants--conventional Al salt (AlCl(3)), polyaluminum chloride (PAC-1) and the purified polyaluminum chloride (PAC-2)--were investigated for the coagulation of humic acid (HA). The results showed the properties of HA flocs depend on which species of aluminum used. The monomeric and dimeric aluminum species (denoted as Al(mono)) formed the largest and strongest HA flocs with longest growth time. The HA flocs formed by Al(13)O(4)(OH)(24)(7+) (Al(13) for short) is the smallest and weakest. The properties of HA flocs made it possible to investigate the relationship between the flocs growth process and aluminum species.

Preparation and characteristics of quaternary amino anion exchanger from wheat residue.

Quaternary amino anion exchanger (QE) was prepared from wheat residue (WR) after reaction with epichlorohydrin and triethylamine in the presence of N,N-dimethylformamide and catalyst. The single influential factor experiments and orthogonal tests were carried out in order to obtain the optimal conditions for the preparation of wheat residue quaternary amino anion exchanger (WR-QE). The parameters of the influential factors, which included the types of catalysts, the amounts of WR and triethylamine, and experimental temperatures (activating temperature, catalytic temperature and reacting temperature) were also defined. The results indicated that pyridine was a suitable catalyst, and the catalytic temperature was a key factor of experimental temperatures. The optimal synthesis reaction parameters of dosages were WR:epichlorohydrin:pyridine:triethylamine=2g:20ml:15ml:30ml. Optimal experimental temperature was 100 degrees C. Under these conditions, the nitrogen content of WR-QE was 6.0%, compared with WR of 0.4%. The yield was 556.3%. Nitrate removal was 89.1%; this was higher than the nitrate removal of wheat residue tertiary amino anion exchangers (WR-TE) of 6% -10%.

[Adsorption kinetics of phosphate from aqueous solutions onto modified corn residue].

The adsorption kinetics of phosphate from aqueous solutions onto modified corn residue was studied in a hatch reactor. The influence of initial pH, concentration and temperature to adsorption effect were investigated. In addition, the kinetic data were fitted by pseudo-first-order equation, pseudo-second-order equation, modified pseudo-first-order equation and intra-particle diffusion model, and the respective characteristic rate constants were presented. The results showed that the adsorption data fitted Freundlich isotherm model, and the maximum adsorption capacity of phosphate would decrease with the temperature increasing. Furthermore, the adsorption process could reached equilibrium in 30 minutes, and the pseudo-second-order equation and intra-particle diffusion model generated the best agreement with the experimental data for the adsorption systems. The intra-particle diffusion was the main rate-controlling step. With increasing initial concentration, the rate constant of pseudo-second-order equation decreases and that of intra-particle diffusion model increases. The adsorption kinetic analyses could be of a great practical value for the technological applications of phosphate removal from aqueous solutions.

[Coagulation performance and mechanism of Alb species in polyaluminum chloride in removing humic acid].

Alb species [Al12 AlO4 (OH)24(7+)] is multinuclear hydroxyl compound formed in PAC hydrolysis-polymerization process, with properties of small particle sizes, much positive charge, high aggregation degree and large molecular weight. Alb species was purified from PAC containing high concentration of Alb species using ethanol-acetone mixed precipitation method. The influence of dosage, pH and inorganic ions on humic acid removal from simulative water was studied by measuring zeta potential and UV254. The PDA output (FI curve) was analyzed and the relationship between the parameters (S1, S2, H1, H2) of FI curve and coagulation mechanism were studied at different Alb dosage and pH. When the dosage was 4.3 to 6.3 mg x L(-1) and pH was 3.0 to 6.0, the highest humic acid removal efficiency was obtained. The existence of NH4+, SiO3(2-) and H2PO(-) inhibits the coagulation performance. The results of coagulation kinetics and Zeta potential studies revealed that Alb acted mainly by charge neutralization as well as adsorption bridge building in water treatment.