Study On Coagulating Precipitation For Dressing Wastewater Of Multi-metals Ore

Abstract:Dressing wastewater has significant properties, such as high content of suspended substances and many species of pollutants. It is very important to cleanup the dressing wastewater for both reducing the pollution for receiving waters and improving the quality of water environment. In this study, polysilicate-aluminum-ferric-sulfate (PSAFS) and organic polymer flocculant was prepared to evaluate the coagulation capacity for dressing wastewater of multi-metals ore. The results were mainly as follows:The optimized components of PSAFS for multi-metals dressing wastewater were w(SiO2)=2.0%, n(Fe+Al)/n(Si)=2:1and n(Fe)/n(Al)=1:1. Using the improved Ferron timed ncomplex colorimettic method, the content of Al and Fe in inorganic polymer flocculant PSAFS can be measured synchronously, the distributions of [(Fe, Al)](a) and [(Fe, Al)](b) were accounted for45.7%and48.6%, respectively, and the activity of activated silicic acid had significantly been increased with the addition of aluminum and iron in PSAFS according to SEM and XRD analysis. Treating with60.75mg/L of PSAFS optimized (accounted with the content of Al) in dressing wastewater of multi-metals ore, the residual quanlity of turbidity was71NTU, the concentrations of COD in wastewater cleaned was73.6mg/L, and those of As, Be and Pb were only33.9,0.2and13.2μg/L after15-18min, respectively, and can meet the National Integrated Wastewater Discharge Standard (GB8978-1996).The floc precipitation can be significantly enhanced by flocculant of PSAFS-MC. The optimal combination conditions for PSAFS-MC are pH value of2.2, the concentration rate of MC to PSAFS of0.04, and combined reaction time of8h. When the pH of dressing wastewater is6, the stirring speed of200r/min for1min, treated dressing wastewater with20.24mg/L of PASAFS-MC optimized, the concentrations of turbidity and COD in wastewater cleaned are only46NTU and60.3mg/L, and those of As, Be and Pb in wastewater are only12.7,2.4and1.8μg/L after7-9min, and more, those of Al and Fe in wastewater cleaned are only0.4and1.1mg/L, respectively. Dressing wastewater cleaned can meet the National Integrated Wastewater Discharge Standard (GB8978-1996).The speciation of heavy metals in flocs was analyzed according to the BCR continuous extraction program. The forms of As and Be in floc by PSAFS were mainly existed in reducible, that of Pb was mainly in acid soluble. At the same time, form of As in floc by PSAFS-MC was mainly existed in oxidizable, that of Be was mainly in residual and that of Pb was mainly reducible, respectively. Based on the results from TCLP method, the leaching toxicity of leachates from the flocs by both PSAFS and PSAFS-MC flocculant can meet the National Integrated Wastewater Discharge Standard (GB8978-1996). Heavy metals in the floc can meet the Identification Standards for Hazardous Wastes-Identification for extraction toxicity (GB5085.3-2007). The flocs were stable and safe for heaps.39figures,14tables and111references were included.