Study on arsenic removal in aqueous chloride solution with lead oxide

摘要

A new method to remove arsenic from aqueous chloride solution by using lead oxide was proposed, and the effects of the lead(II)/arsenic(V) molar ratio (n(Pb(II)):n(As(V))), initial pH of solution, initial concentrations of chloride ion (Cl-) and arsenic(V) on arsenic removal were investigated. The results showed that n(Pb(II)):n(As(V)), initial pH and initial Cl- concentration had great influence on arsenic removal. The suitable conditions of arsenic removal were initial pH of 1.8-2.4 and initial Cl- concentration of 0.52-2.00 g L-1 for 200 mg L-1 As(V) solution. Initial As(V) concentration had little influence on arsenic removal when the appropriate n(As(V)):nCl- was controlled in the solution at n(Pb(II)):n(As(V)) of 1.52. Based on these conditions, As(V) removal efficiency reached up to 99.99% and As(V) concentration decreased from 200 mg L-1 to less than 0.01 mg L-1 at initial pH of 1.8 with n(Pb(II)):n(As(V)) of 2.12. Various characterizations confirm that the formed precipitate was mimetite (Pb-5(AsO4)(3)Cl) and had better thermal stability within 500 degrees C. For the prevalent problem of lead dissolution by forming mimetite, Pb residual concentration reduced from 337.6 to 0.07 mg L-1 using sodium sulfide in the solution after arsenic removal. Therefore, lead oxide could be used as an effective reagent of arsenic removal to remove As(V) from aqueous chloride solution.