Study On The Removal Of Heavy Metals From Wastewater By Aluminum Carbon Micro Electrolysis

Based on the current research status of micro electrolysis in water treatment,aluminum-carbon micro electrolysis was adopted to study the removal efficiency of six kinds of common heavy metal ions(Cr???,Cu???,Pb???,Ni???,Cd???,Zn???by taking aluminum scraps and saturated activated carbon particles as the experimental materials.The influences of settling time,the mass ratio of aluminum?iron?and carbon?Al/C or Fe/C mass ratio?,initial pH,oscillation speed and oscillation time on the micro electrolysis of Al/C and Fe/C were investigated by single factor experiment.The order of the influencing factors and the optimal reaction conditions of aluminum carbon micro electrolysis were determined by orthogonal experiment.Based on the analysis of the surface morphology and material composition of aluminum chips and activated carbon before and after the reaction,the mechanism of aluminum carbon micro electrolysis treatment of different heavy metal ions was studied,and the removal ways of different heavy metal ions were described.The research contents and results are as follows:?1?The results of single-factor experiments show that,according to the metal activity sequence and the redox potential,the removal rate of Cu???,Cr???,Pb???,Ni???,Cd???and Zn???by aluminum carbon micro electrolysis decreases in order.With the increase of settling time,the removal rate of all metal ions increased,and gradually stabilized after 40-60min.the oscillating effect can greatly improve the removal rate,shorten the settling time of aluminum carbon micro electrolysis,promote the surface renewal of aluminum carbon,and alleviate the aging of aluminum carbon.The initial pH value mainly affects the electrode reaction of the primary battery,under acid condition,the electrode reaction of primary battery is violent,and gradually decreases with increasing pH.However,due to the fact that aluminum is amphoteric,it still has certain activity under neutral and alkalescent conditions.In addition,the pH will affect the production of metal ion hydroxide precipitation.Depending on the solubility product of the metal hydroxide,the difficulty of precipitation of the resulting hydroxide varies.The change of Al/C mass ratio mainly affects the number of primary batteries.When the Al/C mass ratio was 2:1,the quantity of primary batteries reaches the maximum,and the removal rate of metal ions is the best.The appropriate oscillation speed makes the aluminum chips,activated carbon and the simulated heavy metal water sample to be treated fully contact,thus improving the removal rate.Therefore,the optimal oscillation speed of several heavy metal ions is 100-150r/min.?2?Under the same conditions,different heavy metal wastewater was treated by iron-carbon micro electrolysis.The aluminum-carbon micro electrolysis and iron-carbon micro electrolysis were compared to treat the same heavy metal simulated water sample.The aluminum-carbon micro electrolysis has better removal effect,and the pH range of aluminum-carbon micro electrolysis is wider.It was proved that the removal efficiency of heavy metal ions could be greatly improved by using aluminium-carbon micro electrolysis instead of direct reduction of aluminium or iron-carbon micro electrolysis.?3?The results of orthogonal experiment show that the influence order of each factor on different heavy metals is different,and the optimal treatment conditions are also different.Under the optimum conditions,the removal efficiency of Cr???,Cu???,Pb???,Ni???,Cd???and Zn???by aluminum-carbon micro electrolysis can reach the highest value of 95.40%,99.81%,99.16%,97.48%,96.06%and 88.04%.Compared with the single factor experiment,the orthogonal experiment greatly improves the removal rate of heavy metal ions,making aluminum-carbon micro electrolysis as a pretreatment method plays an important role in the treatment of heavy metal wastewater.?4?Scanning Electron Microscope?SEM?,Energy Dispersive X-ray Spectrometer?EDS?and X-ray Photoelectron Spectroscopy?XPS?were used to analyzed the variations in surface physical morphology and composition of aluminum scraps-activated carbon particles before and after the operations.Combined with the principle of corrosion metals and the characteristics of heavy metal ions,and to study the mechanism of the removal of heavy metal ions by aluminum-carbon micro electrolysis.The mechanism including the reaction of primary batteries,the reduction of zero valent aluminum,replacement,Neutralization and the adsorption and coprecipitation of Al?OH?₃ colloidal flocculant.It is inferred that aluminum scraps is the main place for redox reactions,activated carbon is the main site for flocculation and coprecipitation.