Study On Removal Of Lead And Cadmium In Acid Mine Wastewater By Sepiolite

The discharge of waste water generated by mining of our annual of total emission of waste water of the country's industrial over10%and processing rate less than5%.Its greatest damage is acid waste water generated by mining. The mining acid waste has low pH and contain multiple heavy metal ions of sub-standard.If discharge directly will heavily pollute the mine surrounding water,soil ecological environment and harm to human health. Absorption method has advantages of simple operation, good treatment effect, low operating costs, quite applicable for economically underdeveloped and farway regions in a number of metal ions processing. Sepiolite is a natural mineral resources,more produce in jiangxi leping, hunan liuyang and other places in our contry,and has high specific surface area and great absorption capacity.Screening experiments carry on to remove Pb2+and Cd2+by Selecting Fe, attapulgite clay, Sepiolite,zeolite and zero-valent iron as adsorbent.The results indicate that the five adsorbents are all effect obviously to removel heavy metal ions under acidic conditions. The adsorption removal rate of Pb2+is:sepiolite> zero-valent iron> zeolite> attapulgite clay> Fe; The adsorption removal rate of Cd2+is:sepiolite> attapulgite clay> zeolite> Fe> zero-valent iron.Sepiolite amount, adsorption time, initial concentration of heavy ions, concentration of salt solution and mixed heavy metal ions are the major factors to effect the adsorption effect of Pb2+and Cd2+When the sepiolite amout arise from0.2g to1.0g, the adsorption removal rate can be obtained from81.5%to97.7%. The removal rate rises as time increases and while it is1.5h reached equilibrium state. Sepiolite amount, adsorption time and initial concentration and pH of heavy metal ions are the major factors to effect the adsorption effect of Cd2+. After reaction5min, the removal rate of Cd2+is98.3%when dosage of sepiolite is8g,while the removal rate of Cd2+is43.0%when dosage of sepiolite is1g in the200mL and lmg/L cadmium solution.pH of solution range from2to7, the affect of adsorption effect of Cd2+is not a single linear relationship.The best range of pH of the removal of Cd2+by sepiolite is4to5.Investigate removal effect of salt solution on the adsorption of heavy metal ions. Four salt ions Na+,K+,Mg2+and Ca2+on the removal of the rate of Pb2+and Cd2+increases as the initial salt concentration rises. Strength of relationship about the four salt ions on removal rate of Pb2+is:K+> Ca2+> Na+> Mg2+. Strength of relationship about the four salt ions on removal rate of Cd2+is:K+> Ca2+> Na+> Mg2+.The mixed heavy metal ions Cu2+,Zn2+,Mn2+and Ni2+adsorption experiment on activated sludge showed that the remove rate of Cd2+is decrased from98.8%to26.7%and the affect on Pb2+is negligible.compare with mixed heavy metal ions and SO~2-that the content of all metal ions reduces and will be helpful to the adsorption.