Experimental Study On Internal Electrolysis Treating Chromium-containing Heavy Metal Wastewater Enhanced By Ultrasonic

With the development of industry,the pollution of heavy metal wastewater in our country is becoming more and more serious,which brought great harm to ecological security.The chromium containing wastewater has a large amount of discharge and high toxicity,so it had attracted the attention of quite a few people to make a proper way to dispose this heavy contamination.It researched on three ways to treat the water with chromium?Cr?VI??in this paper,which were iron treatment technology,iron-carbon internal electrolysis and iron-carbon internal electrolysis combined with ultrasonic.The main content of this research contains the single factor experiments and response surface methodology.In the meanwhile,materials concentration during in reaction,the surface morphology of iron scrap,the reuse of iron and carbon and kinetics of iron-carbon internal electrolysis were also studied.The results of experiments showed the best reaction conditions of each method.The optimum conditions of iron treatment were that pH value was 2,rotating speed was160rpm,reaction time was 90min,concentration of iron scrap was 30g/L,the size of iron scrap was between 0.5 to 2.0mm.The optimum conditions of iron-carbon internal electrolysis were that pH value was 2,rotating speed was 160rpm,reaction time was 60min,concentration of iron scrap was 30g/L,the size of iron scrap was between 0.5 to 2.0mm.The optimum conditions of ultrasound/iron-carbon internal electrolysis were that pH value was2.5,ultrasonic power was 100W,reaction time was 40min,concentration of iron scrap was30g/L,the size of iron scrap was between 0.5 to 2.0mm.All the three methods can remove Cr?VI?to 90%above,but only ultrasound/iron-carbon internal electrolysis can remove Cr?VI?with short reaction time,mild pH condition and long range of iron size.During the process of iron-carbon internal electrolysis,the iron release amount of Fe²⁺,and then be oxidized to Fe³⁺,in the final it turned into precipitation of hydroxide on the surface of iron scraps.The Cr?VI?in the wastewater was restored to Cr?III?,and turned into sediments at last.The iron scraps and carbon scraps can be reused in the process of internal electrolysis.The process of Cr?VI?removed by iron-carbon internal electrolysis followed the first-order kinetics.