Method Researching For Nickel And Copper Wastewater From Aluminum Alloy Processing

In this thesis,the treatment of nickel-occurring wastewater originated from aluminum alloy production is focused.Biochar was synthesized for using as a sorbent for nickel adsorption from waste sawdust of pine wood by using pyrolysis under controlling conditions.Post modification of the biochar was conducted using heat treatment of biochar with HMTA under CO₂ atmosphere?BC1?,either CO₂?BC2?or HMTA?BC3?alone.Meanwhile,chemical precipitation of nickel ion was conducted by using acetylene sludge as a precipitating agent.Based on obtained experimental data from modified biochar adsorption and chemical precipitation,a combined process of acetylene sludge precipitation followed by biochar adsorption is proposed for final treatment of nickel-occurring waste water.The resulting modified biochar was characterized by BET,FTIR and Boehm for clarifying its porous structure and surface chemistry.Adsorption performance of modified biochar for nickel and copper ions in the dilute wastewater was measured in bench experiments and the competitive adsorption of both nickel and copper ions in a co-occurring system was carried out on modified biochar.It has been shown that sample BC3 displayed the largest specific surface area among in all modified biochars,and BC2 has the same specific surface area as the unmodified sample,while BC1 possessed the smallest in specific surface area.On the other hand regarding the oxygen functional groups,BC1 displayed the highest oxygen functional group content,BC2 ranked at the second,and BC3 was of the lowest,which plays an important role in the adsorption of nickel and copper ions.Adsorption of nickel and copper ions resulted in96.5% of removals under corresponding optimum conditions of pH4⁷ and 4⁶,contact time of 6 h and 4 h,dosage of 2 g/L,2.5 g/L,3 g/L and 1 g/L,1.5 g/L,2.0 g/L,respectively for nickel and copper ions.Moreover,adsorption of copper is higher than nickel for all samples while BC1 is the best adsorbent among other two.Langmuir isothermal model is adequately to describe the isothermal adsorption data of nickel andcopper and the the pseudo-second-order kinetic model is well agreed with the kinetic data of two ions.In competitive adsorption,mutual inhibition occurred among two ions due to the competently occupying of active sites on modified biochar,while interestingly,the existence of nickel ion tended to enhance the affinity of copper ion on BC3.Chemical precipitation with carbide slag plus acetylene sludge exhibited that by dosing 1.6 g/L carbide slag,the treated water can match the currently used national standard.On the other hand,the heavy metals occurring in the nickel-containing waste water can be removed nearly completely by using the modified biochar,BC1,with a dosage of 2.5 g/L at pH for 6 h.Rough estimation of economic profit using different methods for meeting the current standard of nickel-occurring waste water gave the cost of precipitation at 0.22 yuan/t while adsorption at 24 yuan/t.Consequently,it could only be industrially feasible if a combination of chemical precipitation with carbide slag-acetylene sludge followed by modified biochar adsorption,which the rough estimation of economic prifit using co-treatment will give the cost at 0.66 yuan/t.