Four magnetic anion exchange resins (MAERs) were used as adsorbents to purify drinking water. The effect of water quality (pH, temperature, ionic strength, etc.) on the performance of MAER for the removal of dissolved organic matter (DOM) was also investigated. Among the four studied MAERs, the strong base resin named NDMP-1 with high water content and enhanced exchange capacity exhibited the highest removal rate of dissolved organic carbon (DOC) (48.9% removal rate) and UV-absorbing substances (82.4% removal rate) with a resin dose of 10 mL/L after 30 min of contact time. The MAERs could also effectively remove inorganic matter such as sulfate, nitrate and fluoride. Because of the higher specific UV absorbance (SUVA) value, the DOM in the raw water was found to be removed more effectively than that in the clarified water by NDMP resin. The temperature showed a weak influence on the removal of DOC from 6 to 26°C, while a relatively strong one at 36°C. The removal of DOM by NDMP was also affected to some extent by the pH value. Moreover, increasing the sulfate concentration in the raw water could decrease the removal rates of DOC and UV-absorbing substances.
A series of biodegradable amphoteric chitosan-based flocculants(3-chloro-2-hydroxypropyl trimethyl ammonium chloride(CTA) modified carboxymethyl chitosan,denoted as CMC-CTA) with different substitution degrees of CTA were prepared successfully.The content of carboxymethyl groups in each CMC-CTA sample was kept almost constant.The solubility of the various flocculants showed that,higher cationic content of flocculants caused a better solubility.The flocculation experiments using kaolin suspension as synthetic water at the laboratory scale indicated that the substitution degree of CTA was one of the key factors for the flocculation properties.With the increase of cationic content,the flocculants were demonstrated better flocculation performance and lower dosage requirement.Flocculation kinetics model of particles collisions combining zeta potential and turbidity measurements was employed to investigate the effects of the cationic content of the flocculants on the flocculation properties from the viewpoint of flocculation mechanism in detail.Furthermore,flocculation performance using raw water from Zhenjiang part of Yangtze River at the pilot scale showed the similar effects to those at the laboratory scale.
