Removal Of Manganese And Sulfate From The Polluted Water In Manganese Mine Area

Water pollution in Guangxi manganese mine was a serious threat to the safety water of the residents living around the mining area, the conventional process is difficult to remove manganese in high concentration, sulfate and other pollutants. The purpose of this paper is to find a simple and effective treatment method to remove manganese and sulfate of surface water in mining area. Potassium permanganate preoxidation experiments were conducted in synthetic water and the optimal reaction parameters are that the oxidation time is 2 minutes which followed by coagulation with five minute and then seven minutes for flocculation, and 3KMn O4/2Mn2+(Mn2+=10mg/L) molar ratio is 0.75, 99% of Mn removed were obtained at this condition. According to the reaction stoichiometry, part of Mn2 + was removed by absorbed on Mn O2 formed in-situ. The pH value and the initial turbidity did not have obvious effect on Mn removal. When the initial concentration of manganese ranging from 4mg/L to 14mg/L, Mn concentration of treated waters were less than 0.100mg/L at the optimal condition.Results revealed that potassium permanganate had very good effect of manganese removal when 3KMn O4/2Mn2+(Mn2+=15.120mg/L) molar ratio ranged from 70% to 86%. The average removal efficiency of Mn2+in settled water was up to 99.6% and the residual concentrations of Mn2+ and Ni2+were both below 0.020mg/L. Metal ions can effectively remove without coagulant situation since 324.5mg/L of Ca2+ could enhance the polymerization of Mn O2 formed in-situ. When the pH of solution was above 8, 84.4% Ni removal can be achieved with 84.0% of the molar ratio of 3KMn O4/2Mn2+. pH significantly affected the removal of Ni2+. Ni2+ and Cd2+ were electrostatic adsorbed by Mn O2 since Mn O2 presented a negative surface charge at this pH. The variation of Cd2+ concentration has not effect on the removal of Ni2+, which proved that adsorption sites of Ni2+ and Cd2+ on Mn O2 were difference.Manganese, nickel, cadmium, sulfate and hardness of polluted water sample of a mine area in Guangxi(2015.11-2016.03) exceeded the standard by 45-151, 3.55-6.4, 1.4-3, 2.4-3.3 and 1.7-2.3 times. The removal of manganese, nickel and chromium could be removed efficiently by potassium permanganate pre-oxidation efficient, but sulfate and hardness could not be removed by permanganate pre-oxidation. Sodium metaaluminate and lime milk were dosed to contaminated water(SO42-=606.0mg/L, Ca2+=236.4mg/L, Mg2+= 36.85mg/L)for sulfate, Ca2+ and Mg2+ removing. When Ca(OH) 2 is 284.0mg/L, and Na Al O2 is 3.5m M, and pH ranging from 11.0 to 12.1, and the stirring time was 1h followed by precipitation with 30 min, and adjusted pH back to below 8, and then the final supernatant was precipitated by flocculation, 55.4% of SO42-,and 50.0% of Ca2+,and 99.9% Mg2+ were removed when the Al O2-/SO42-molar ratio was 0.58 at 20?, and the residual concentrations of Mn2+?Al3+?Ni2+?Cd2+?SO42-?Cl-and Na+ were below 0.100?0.200?0.020?0.005?250?250 and 250mg/L, respectively. Part of Ca2 + reacts with with Al O2- and formed aluminum calcium precipitation. pH significantly affected the removal of sulfate, and the highest removal of sulfate was achieved when the initial pH was 12.1. The residual aluminum concentration was also very high at this situation, which could promote the following process of flocculation-precipitation with a pH adjustion.