Synthesis Of Efficient And Low-cost Adsorbent For The Removal Of Heavy Metal Ions From Electroplating Wastewater

With the quick development of economy and society,environmental problem is receiving increasing attention.During past decade,heavy metal pollutants derived from the wastewater of electroplating industry have emerged as one of the most serious issue that need to be resolved in China.Although the tremendous progress has been made in the field of heavy metal treatment,the development of high efficiency and low cost techniques is still a significant challenge to meet the increasingly strict emission standards.To provide a new and potential technique,this work focuses on the low-cost inorganic absorbent materials aimed at the practical electroplating wastewater.The major results have been summarized as follow:(1)New inorganic absorbent was successfully synthesized by a facile hydration reaction of Portland cement.Its high adsorption capacities for Cu.U and Ni21 mainly originate from three aspects:(a)the chemical reaction between the cement-derived calcium silicate hydrate(i.e.,the major ingredient of the as-obtained inorganic absorbent)and heavy metal ions,(b)the negatively charged surface,(c)the physical absorption.(2)By optimizing the technical parameters,such as the weight ratio of the absorbent to heavy metal ions,pH value of wastewater,particle size of absorbent,and adsorption time,the as-obtained absorbent has shown a bright prospect in the removal of Cu2+ and Ni2+ from the acidic electroplating wastewater.(3)When used as an adsorbent for the electroless nickel plating wastewater,the as-obtained absorbent not only exhibited high capacity of Ni2+ removal,Dut also has a certain treating effect on total phosphorus,chemical oxygen demand,and ammonia nitrogen.In addition,the introduction of a small amount of NaCIO during the adsorption process would help to ensure that the treated wastewater can meet the emission standard([Ni2+]<0.1 mg/L).(4)To meet the emission standard for Cu2+([Cu2+]<0.3 mg/L)in the terminal wastewater or integrated wastewater,the adsorption capacity of the as-obtained absorbent can be further improved by adjusting pH and introducing Fe3+ in the adsorption process.Based on this strategy,the as-obtained absorbent also can be applied in the treatment of non-cyanide copper plating wastewater.(5)Without using any adsorbent,a Fe3+/sunlight system was further developed to treat the citrate-containing non-cyanide copper plating wastewater.The Fe2+ and free radical generated by the photodegradation of the Fe3+-citrate coordination compound can efficiently drive the reduction of Cu2+ to Cu2O and Cu,resulting in high removal capacity for Cu2+.