Removal of Hexavalent Chromium and Turbidity in Drinking Water by Chitosan

The threat of heavy metal pollution in water sources becomes increasingly serious. Toxic hexavalent chromium is harmful for health. Chitosan is a non-toxic and pollution-free substance, it is a cationic coagulant after protonated in diluted acid solution, it also can complex for many heavy metal ion. The study on removal of Cr (VI) and turbidity in drinking water by chitosan in this paper was performed. The results showed that the removal efficiency of Cr (VI) decreased with increasing pH, the removal rate of Cr (VI) was as high as 100% at pH4 using the chitosan concentration of 1.0g/L, but in these conditions, the turbidity was not removed. The removal efficiency of Cr (VI) bore relationship to stirring time of slow mixing step and initial concentration of Cr (VI). The best stirring time was 4 hours. To attain a good removal efficiency of Cr (VI), the dosage of chitosan must increase with the initial concentration of Cr (VI) increasing. At pH7, low chitosan dosage had good turbidity removal.