Experimental Study On Treatment Chromium-containing Wastewater By Calcium Polysulfide-Fly Ash Synthetic Zeolite Combination

In recent years,the rapid development of industry has led to the increasing pollution problem,especially the pollution of water resources,which has already posed a serious threat to human living environment and health.Among the many pollutants,chromium due to high carcinogenicity,by the world as a key pollutant remediation object.In contaminated water,chromium is usually in the form of Cr(?)and Cr(?),the toxicity Cr(?)is greater than trivalent chromium,but under certain conditions,the two can be transformed between each other.Therefore,it is of great practical significance to explore a new approach to remove them at the same time.The paper for the problem of chromium-containing wastewater treatment,taking the mixed wastewater of electroplating wastewater and acid wastewater discharged from an electroplating factory as the research object,using theoretical analysis and laboratory experiments combined,static experiments and dynamic experiments combined,chemical reduction and physical adsorption combined with the research methods,based on the basic theory of water engineering and indoor experimental monitoring data as the basis for research.First,through the indoor static single factor test,the effects of reaction time,dosage,solution pH and initial solution concentration on Cr(?)and Cr(?)treatment were investigated,to obtain the best reaction conditions of agent and adsorbent.Then,based on the single factor test results,experimental study on treatment of acidic electroplating wastewater by reactive agent-adsorbent by response surface method,get the best reaction conditions.Finally,using the dynamic test method,the effects of adsorbent type,adsorbent filling amount and hydraulic retention time on Cr(?)and total chromium penetration curves were investigated,analysis of the dynamic conditions to achieve the best results of the process conditions,to provide experimental guidance and theoretical basis for the practical engineering of wastewater containing chromium.Specific test results are as follows:(1)The effects of several reducing agents on the removal of Cr(?)in chromium wastewater were compared,CaSx reaction speed,pH adaptability,high removal rate,no pollution,identified as the best reducing agent.The results showed that increasing the dosage of the agent,increasing the reaction time,reducing the pH of the solution,and diluting the chromium-containing wastewater are beneficial to the reduction of Cr(?)in the chromium-containing wastewater by CaS_x.(2)Compared with a variety of adsorbents,the adsorption effect of zeolite on Cr(?)was better than that of other adsorbents.Under optimal conditions,the treated waste chromium content meet the emission standards.The adsorption kinetic test results show that the adsorbed Cr(?)by zeolite synthesis can be described by Langmuir adsorption isothermal model and quasi-second order kinetic equation.In structure,fly ash synthetic zeolite has a rough surface and larger specific surface area,which is favorable for the adsorption of Cr(?).In terms of removal effect,under the same conditions as the adsorbent,the fly ash synthetic zeolite has a high removal rate for Cr(?).Based on the above analysis,the adsorbent used fly ash synthetic zeolite.(3)On the basis of single factor test,experimental study on BBD response surface method for CaS_x and fly ash synthetic zeolite combined with chromium wastewater test.The experimental results show that the model is reasonable and reliable.Under this condition that CaS_x dosage is 1.8 times the theoretical dosage,synthetic zeolite dosage of about 15g/200mL plating chromium wastewater and pH=3.87,the removal rate of Cr(?)was 99.98%and the total chromium removal rate was 99.94%,which was consistent with the predicted value.(4)CaS_x and fly ash synthetic zeolite treatment of chromium-containing wastewater dynamic test results show that the factors such as the type of adsorbent,the height of the adsorbent layer and the influent flow rate have a significant effect on the penetration curve of total chromium.Under the same conditions,the adsorption time of natural fly ash is shorter and the adsorption effect of synthetic zeolite is better.With the synthesis of zeolite as adsorbent,the adsorption layer height is inversely proportional to its penetration time.The greater the flow rate of the inlet,the shorter the permeation time.And these factors have little effect on the removal of Cr(?).