Study On The Analysis And Treatment Of Pollutants In Environmental Samples

Environmental pollution is a severe fact that the human faces in the process of development and subsistence. Water pollution and organism contamination are two primary aspects of environmental pollution. It is an important problem that the analysis and treatment of pollutants and heavy metals in particular are studied. This work is divided into two parts: one is concerning sewage treatment and recovery of cadmium( II) from water; another is about the analytical methods of Hg, As, Pb, Cu in traditional Chinese medicines and biological samples.Chitosan as a flocculant used to dispose organic wastewater containing Cu( II), comparison of flocculating effect between chitosan and A12(SO4)3 , synthesis of porous chitosan and cross-linked chitosan gel beads for removal of Cd( II ) from water, as well as sorption performance and mechanism of gel beads for adsorption Cd( II) were investigated in the upper part of this work. The details are as follows:1. Chitosan, a flocculant, was used to dispose organic wastewater containing Cu( II). The factors that effected results of flocculation were the amount of chitosan and pH of organic liquid waste. The flocculating result had no concern with stirring time. The range of suitable pH was from 5.5 to 6.5. The amount of chitosan varied with COD and turbidity of wasted water. Chitosan could chelated, adsorb and remove large quantities of copper. The results of decreasing turbidity and Cu2+ were satisfactory. The precipitate lowered quickly. The turbid concentration of wastewater was reduced over 98%. A little COD was depressed because there were amounts of dissoluble organic matter in water. A12(SO4)3, a conventional flocculatingagent, was investigated to treat waster liquids. The experiment indicated that the best favorable pH was 5.70-6.50, the turbidity was decreased obviously when A12(SO4)3 was used. The contrast test showed that A12(SO4)3 could not decrease the concentration of noxious heavy metal copper. Chitosan brought about a better flocculating effect than A12(SO4)3. The precipitates of chitosan were formed among which dispersed phase was mixed after flocculation. We can draw a conclusion that the mechanism of chitosan flocculating organic wastewater is electrostatic force and chitosan is a efficient positive ionic flocculating agent.2. The dissociation constants of chitosan in aqueous solutions have been investigated by potentiometric titration. The potentionmetric behavior is well described by the Katchalsky s equation. The pKa. varies with the ionic strength and is dependent of the added salts, the corresponding value is 6.170, 6.382 (O.lmol/LNaCl), 6.390 (O.lmol/L KC1), 6.592 (0.5 mol/L NaCl), 6.725 (0.5mol/L KC1) respectively. The above values of pKa explained salt effect of metal adsorption on chitosan.3. Porous chitosan gel beads have been prepared and have shown enhanced sorption performance in batch systems. In well-mixed batch adsorption experiments, sorption capacity of 1.6mm diameter beads could reach 258mg/g. The sorption rate was fast enough to reach adsorption equilibrium in 4h. When KC1 existed in CdCl2 solution, the saturation capacity for adsorption of Cd( II) on chitosan increased with increasing concentration of KC1. The NH2 group in chitosan combined Cd( II) in the form of CdCl2. The compositions and bonding energies of elements C, O and N in the surfaces of chitosan and Cd( II )-chitosan complexes were determined by X-ray photoelectron spectrometry. The interaction mechanism of chitosan and cadmium ion was investigated. The chemical shifts of the nitrogen atoms showed that the amine groups of glucosamine residues were the active sites of interaction with the cadmium ions. The calculated value of the N/Cd ratio from XPS and chemical analysis was 1.6. Both physical adsorption and chemical adsorption occur between Cd( II)and -NH2 on the surfaces of chitosan. Two ligand atoms of N are attached to a metal ion of Cd( II) in the chemisorption. Equilibrium isotherm for adsorption Cd( II) on chitosan were measured. The experimental data...