Coprecipitation Characteristics Of Amphiprotic Heavy Metals In The Process Of CO₂Areation Of Fly Ash Wash Water Lotion

Human will produce large amounts of municipal solid waste worldwide eachyear, so far, incineration is the main method of processing municipal solid waste.However, this method will produce a lot of incineration fly ash which contain avariety of heavy metals (such as Pb, Zn, Cu, Cd), the environmental protection andthe commonly used method processing incineration fly ash is cement solidification.Raw fly ash water must be washed first to remove most of the Cl and large amountsof heavy metals inside of them in order to avoid the leaching of heavy metals incement. Meanwhile, a large number of heavy metals and Cl was located in the fly ashwash water, which also contains a lot of Fe3+, Al3+, Ca2+ions. That also createdconditions to CO2aeration processing fly ash wash water, which also reduce thegreenhouse gas CO2from the atmosphere.Fly ash wash water lotion contains Na+, K+, Ca2+, Mg2+, Fe3+, Mn4+, Cl-, SO42-,Pb2+, Zn2+, Cu2+and Cd2+and other ions. The heavy metal ions Pb2+, Zn2+, Cu2+andCd2+will contaminate groundwater and should reduce as far as possible. Research hasshown that the Fe3+, Al3+ions in the fly ash wash water can form complex Fe(OH)3(s) and Al(OH)3(s), both hydrated oxide has certain adsorption to heavy metals,especially for those which has less molarity than colloid adsorbent itself. When flyash wash water lotion contains dissolved CO2, a large number of Ca2+and CO32-ionswill form sediment CaCO3(s). Studies have shown that calcium carbonate to havecertain adsorption effect of heavy metals.Phreeqc was used to simulate the process which inlet CO2into the fly ash washwater solution. With continuous pass of CO2into the solution, the pH of solutiondecrease gradually, The coprecipitation situation of four kinds of heavy metal Pb2+,Zn2+, Cu2+and Cd2+is as follows: When the pH is in10.6~13.5, the main sedimentof Pb is Pb(OH)2(s), the pH in8~10.5, Pb is mainly adsorbed by calcium carbonateand complex gel, the pH in6~8, Pb is mainly adsorbed by calcium carbonate; Whenthe pH range is11.5~13.5, the main sediment of Zn is Zn(OH)2(s). When the pH range is6~11.5, Zn is mainly adsorbed by calcium carbonate; When the pH rangeis11~12.5, the main sediment of Cu is Cu(OH)2(s). When the pH range is8~11, Cuis mainly adsorbed by calcium carbonate and complex gel adsorption. When the pHrange is6~8, Cu is mainly adsorbed by calcium carbonate; When the pH range is13.3~13.5, the main sediment of Cd is Cd(OH)2(s). When the pH range is6~13.3, Cdis mainly adsorbed by calcium carbonate;...