The Recycle Of Salt Mud And Its Application Research In Dye Wastewater Treatment

Salt mud is the mud that discharged by the caustic soda enterprises in the brine refining process, which belongs to industrial solid waste, and the treatment of salt mud is an urgent problem. The resource utilization of salt mud can reduce waste salt mud pollution to the environment, and make waste profitable, which will get environmental benefits, social benefits and economic benefits in the near future.In this paper, the discharged brine sludge of caustic soda plant was used as raw material, which chemical components was analysized, and a comprehensive utilization program for resource recovery was designed. The recycling products were characterized by the X-ray diffraction (XRD), infrared (FT-IR), scanning electron microscope (SEM), thermogravimetric (TGA) and so on. Its application in dye wastewater was also studied. The main contents and conclusions are as follows:(1) The salt mud component measurement results showed that:magnesium hydroxide, calcium carbonate, sodium chloride, iron hydroxide and the insoluble soil impurities, contents of each component determined by EDTA and ICP-OES were:8.70%,78.45%,11.30%,0.95%, and 0.60%.(2) The leaching tests of calcium and magnesium of salt mud were studied. The magnesium hydroxide and calcium carbonate products were separated through stepwise precipitation, and the effects of pH on its purity and yield were also studied. The obtained optimum leaching conditions of calcium and magnesium was:temperature of 70℃, acidity of 2.0 mol/L, stirring speed at 300 r/min, and liquid to solid ratio of 4:1. The optimum pH of secondary impurity of iron hydroxide was 9.2-9.4, the optimum pH for the precipitation of magnesium hydroxide was 10.6, and the pH for the precipitation of calcium carbonate completely was around 9.0.(3) The resulting products were characterized. It showed that magnesium hydroxide product was higher than the known HG/T3607-2007 industrial standard, calcium carbonate product higher than the excellence in goods of HG/T2226-2010 standard. The obtained products have high purity, good thermal stability, small particle size, and a certain morphology.(4) The production capacity of 20 Wt/a caustic soda discharged near 10000 tons of salt mud, assessing its industrialization resource utilization feasibility of 10000 tons of salt mud, and analysing its technical and economic. The resualts showed that the comprehensive utilization of caustic soda salt mud industrialization is feasible.(5) The salt mud was dried after desaulted with salt to absorb Rhodamine B wasterwater. It showed that the removal rate of Rhodanmine B could reach more than 93% when Rhodamine B initial concentration was 10 mg·L-1, and the adsorbent dosage was 20 g·L-1, the initial of pH value was 4.3, the adsorption reaction temperature was 25℃.The salt mud can effectively absorb the Rhodamine B simulate organnic pollutant, according with the Langmuir isotherm equation. The adsorption capacity of Rhodamine B for salt mud was 0.33 mg/g, and the adsorption equilibrium constant was 2.26 L/mg. After Rhodamine B was adsorbed by salt mud, Rhodamine B can be effectively removed from salt mud when calcined at 400℃.