Removal Of Thallium During Enhanced Coagulation And Filtration By Nanoscale Manganese Dioxide

In recent years, heavy metal pollution events in water frequently happenthroughout our country, and thallium pollution has become increasingly serious.Because of its toxicity and bioaccumulation, thallium attracts people’s moreattention. Manganese oxides are widespread in the natural environment, playing animportant role in the process of migration and transformation of many organic andinorganic components. Manganese dioxide (MnO2) can not only oxidatesulfonamides, bromine phenol and other organic substances, but also remove heavymetal ions in water efficiently with a good adsorption performance. Nanoscaleadsorbent has a larger specific surface area, which has stronger adsorption capacity.In this paper, nano manganese dioxide is used to enhance the process of bothcoagulation and filtration during the conventional water treatment. Analysis andcomparison on the removal efficiency of thallium are listed.In order to facilitate the separation and analysis, we use the particle-MnO2,which is generated by the reduction of potassium permanganate by manganesechloride, for the adsorption experiments.-MnO2adsorption of Tl (I) can becompleted in5minutes with an adsorption capacity of up to769mgTl/gMn.Compared to low pH conditions, MnO2under neutral or alkaline condition is moreconductive to Tl adsorption as a result of more negative surface charge. Thecompetitive adsorptions of Na+and Ca2+lead to their inhibitions on the removal ofthallium. The increase of Mn leakage proves that Tl(I) is oxidized by MnO2underacidic condition. Natural organic matter has no obvious limitation on the removal ofthallium, while inorganic complex anions promote thallium removal.Nano MnO2obtained with sodium thiosulfate reduction of potassiumpermanganate has excellent properties, such as small size, good dispersion andadsorption ability. For nano MnO2enhanced coagulation, the removal efficiency ofTl(III) is slightly higher than that of Tl(I), meaning that pre-oxidation may be takeninto consideration in actual water treatment. Increasing pH value is in favor ofthallium removal, while Ca2+has an inhibition. HA can greatly reduce the removalrate of thallium. Compared with the Mopanshan water, Songhua River has a lowerthallium removal rate, which confirms that natural organic matter is the main factor in coagulation.This study also discusses the effect of nano MnO2in the filtration. Nano MnO2is advantageous to the quartz sand filter, and the effect is proportional to theconcentration of MnO2. The addition of nano MnO2has no significant influence onmanganese which has metal oxide on its surface. In a certain extent, Ca2+reduces theremoval of thallium in the filtration, while HA greatly increases the concentration ofthallium and manganese in the effluent of quartz sand filtration, indicating that HAhas a strong complexing ability of heavy metals.