Comparing the Efficacy Rates of Lime and Poly Aluminum Chloride Coagulants in Cadmium Removal from the Landfill Leachate by Chemical Precipitation

Aims Chemical precipitation is a simple, efficient, and cost-effective method for eliminatingheavy metals found in landfill leachate. The aim of the present study was to compare theefficacy rates of cadmium removal with the coagulants like poly aluminum chloride and limeusing chemical precipitation method.Materials & Methods In this experimental study, the raw studied samples were collectedfrom the landfill located in Kahrizak, Iran, in May 2014. The elimination rates of cadmiumat 1000, 1500 and 2000mg/l concentrations of lime; at 100, 150 200mg/l concentrations ofpoly aluminum chloride; at 7, 9, 11 pH levels; and during 20, 40 and 60min of the reactiontime were studied. Data were analyzed in SPSS 16 software using ANOVA, independent T andrepeated measurement tests.Findings The maximum elimination rate of cadmium in both lime and poly aluminumchloride were seen at pH=11. The maximum rates of cadmium removal occurred at minute40 in 2000mg/l concentration of lime (99.4%) and 200mg/l concentration of poly aluminumchloride (98%).Conclusion Both lime and poly aluminum chloride have the best cadmium removal rate fromleachate at pH=11 after 40 minutes of precipitation process. Being more inexpensive andeasily available than poly aluminum chloride, lime is considered as an appropriate coagulant.

Keywords:

Cadmium , Calcium Hydroxide , Aluminum Compounds , Chemical Precipitation