The Removal Of Arsenic From Drinking Water By Nanofitration Membrane

Arsenic (As) is widespread in the nature, which is first in the list of 19 carcinogens determined by The World Health Organization (WHO). "Living and Drinking Water Hygiene Standards"(GB5749-2006) made MCL of 0.01mg/L of arsenic lower than original 0.05 mg/L. The strict standard requires higher drinking water arsenic removal techniques.Nanofitration (NF) has some advantages different from reverse osmosis (RO) and ultrafiltration (UF). NF can reject organic matter and multivalent ions, and allow monovalent ions through it. NF is one of safe drinking water technologies.The removal of arsenic (As (Ⅴ), As(Ⅲ)) from synthetic water by low-pressure nanofiltration (NF90, NF270, HL) membranes is discussed in the paper. Different operating conditions that affect rejection are studied, such as feed concentration, pH, temperature and operating pressure. To exam the effect of monovalent ions and divalent ions on natural dissolved organic matter (DOM), sodium chloride (NaCl) and magnesium sulfate (MgSO4) are chosen as typical inorganic ions. Humic acid (HA) is used as alternative of DOM. A comprehensive analysis on the mechanism of arsenic removal by nanofiltration membranes is explored as well.The result shows that nanofiltration membrane alone can not get a satisfied removal efficiency to As, expecailly toAs(Ⅲ), so that manganese sand filter is used to combine with NF. Manganese sand can oxidize As(Ⅲ) to As (Ⅴ) , which is much easier to be removed. The concentration of As in effluent is less than 0.01mg/L.