Research On Purification Technology Of Drinking Water Polluted By Thallium

Thallium is accumulative toxicant. Thallium may enter into human body through the breath, drinking water and food chain and other ways, which cause human body acute or chronic intoxication.With the accumulation toxicity of thallium,thallium poisoning can cause permanent lesion to patients. Due to mis-operation or mismanagement and other reasons, some cities in our country also often appear some sudden water pollution incident. The sudden water pollution incident often affect the safety of drinking water.Therefore, the most urgent key project for us to study is to solve how to use purification technology, to meet national drinking water standards and guarantee the safety of drinking water.In this paper, adsorption and oxidation-flocculation methods were used to remove thallium from drinking water.(1) A composite adsorbent was prepared by carboxymethyl chitosan and bentonite, and was used to adsorb thallium in water. The effect of adsorption time, pH and temperature on the adsorption properties of the composite adsorbent to thallium was investigated. The results indicated the adsorptive capacity of carboxymethyl chitosan-bentonite compound adsorbent for thallium in water was enhanced with the increase of pH. The adsorption process was influenced by temperature, when the temperature lower than50℃, it being of benefit to the adsorption with the temperature increase, but when the temperature higher than50℃, it being opposite of the adsorption with the temperature. Adsorption capacity for thallium was bound up with the concentration of thallium. When the initial concentration of thallium was100mg/L, its equilibrium concentration was48.54mg/L, and adsorption capacity was15.43mg/g. The purpose of controlling thallium concentration in yielding water was achieved by changing the amount of adsorbent.(2) Oxidation-flocculation was a new technology based upon recombining current process:oxidation-flocculation-sedimentation-Filtration-disinfection. In water environment,there are mainly Tl+and TI3+. Tl+can form stable complexes, difficult to deposit.But Tl3+is quite the contrary. So it was an effective way of removing Thallium by oxidation.Experimental results indicate that the removal efficiency of thallium can be above90%in four processes. They are NaCIO-PFS, NaC10-PAC,Bleach-PFS and Bleach-PAC. When50mL solution contained3.03mg/L thallium concentration, bleach dosage was0.6mg and PAC dosage was2mL,at pH value of10. Under these conditions, the thallium levels fall to0.05μg/L and the removal rate was99.998%, reaching the National standard of drinking water.