Experimental Study On Treatment Of Nickel Tartrate Wastewater By Alkaline Soil Metal Precipitation

Heavy metal pollution has become one of the most serious environmental problems.Due to the toxicity and cumulative effect of heavy metals in the environment,the recovery of heavy metals has attracted special attention.The treatment of complex heavy metals is a difficult and important point in the treatment of heavy metals.In recent years,various methods for removal of complex heavy metal wastewater have been extensively studied.These technologies include chemical precipitation method,ion exchange method,Fenton method,ferrite method,membrane filtration method,flotation method and electrochemical method,as well as the combination process of various treatment methods.Ion exchange,adsorption and membrane filtration are widely studied in the treatment of heavy metal wastewater.However,chemical precipitation is the most widely used method in the field of industrial wastewater treatment.Based on the chemical precipitation method,this paper proposes a new process for treating complex nickel wastewater by replacement precipitation of alkaline earth metals.The removal efficiency of Ni²⁺by the process combined with ultrafiltration was also studied.Finally,according to the different stability of nickel and cadmium to tartaric acid,a method of treating cadmium and nickel waste by step precipitation was proposed.The results are as follows:1.Tartaric acid complex nickel was removed from wastewater by alkaline earth metal replacement precipitation method.The effects of the dosage of displacement agent,initial pH value of solution,reaction time,reaction temperature,molar ratio of tartaric acid to nickel ion and the kinds and concentration of other coexisting ions in solution on nickel removal were studied.The experimental results show that the removal rate of copper complexes in wastewater from nickel tartrate removal by alkaline earth metal replacement precipitation method can reach more than 90%.When the reaction temperature and time are about 30 C and 30 min respectively,the removal rate can reach94.97%by controlling the pH value of 12 and the molar ratio of Ca?NO₃?₂ to Ni²⁺of 5%.The removal rate of Ni²⁺can reach 80%and 70%respectively when the molar concentration of CO₃^2-and EDTA is 20%of Ni²⁺in solution.2.Alkaline earth metal replacement precipitation ultrafiltration technology was used to treat nickel tartrate wastewater.According to the previous part of the study,it was found that natural sedimentation could not make the sediment clean.After treatment,the turbidity can even reach about 200.It is found that the diameter of particles in water is less than 100 nm by laser particle size analyzer,which belongs to colloidal substance and is difficult to settle naturally.Ultrafiltration process was adopted to further treat wastewater.Similarly,the effects of dosage of displacer,initial pH value of solution,reaction time,reaction temperature,molar ratio of tartaric acid to nickel ion,types and concentration of other coexisting ions in solution on nickel removal were studied.Ni2+removal rate can reach more than 95%under various conditions.When the pH value reaches 12,the removal rate of Ni²⁺can reach more than 99%.3.A method of treating nickel-cadmium wastes by step precipitation was studied.This is a method of separating and recovering nickel and cadmium from the complexes formed by nickel and cadmium ions and tartaric acid with different stabilities.The effect of this method on the recovery of nickel-cadmium batteries was also studied.The crushed waste particles were dissolved and filtered by HCL,then tartaric acid was added to make the molar ratio of tartaric acid and metal?cadmium+nickel?in acid solution reach 1:1,and the mixed solution of metal ions was obtained.NaOH was added to the mixture and then stirred and filtered to obtain a relatively pure solution of cadmium tartrate and nickel tartrate.Then Ca?NO₃?₂ replacement agent was added to the filtrate,and alkali was added to the neutral condition.Calcium tartrate was removed by filtration,and then Ni?OH?₂ precipitation was obtained by adding alkali.The recovery of nickel and cadmium can reach 93.14%and 99.21%respectively.