Abstract: Through the tests on the As³⁺ wastewater treatment for As(Ⅲ) removal by magnesium hydroxide, the effects of reaction time, magnesium dosage, pH value and temperature on As(Ⅲ) removal were explored.The experimental results showed that magnesium hydroxide had an excellent performance in the removal of As(Ⅲ) ions from As³⁺ wastewater with easy operation and a high removal efficiency（up to 99% above).Its absorption isotherm mode matches well with Langmuir adsorption isotherm function,and its maximum adsorption capacity is 4.04 mg/L.

Key words: Magnesium hydroxide, As(Ⅲ), Adsorption, Water treatment