Research On Low-cost Treatment Process Of High-concentration Chromium, Copper And Sulfur Wastewater

This article briefly introduces the environmental hazards and treatment status of heavy metals and sulfur-containing wastewater,and systematically describes the current chemical treatment technology and industrial examples,and then conducts low-cost treatment research work for high-concentration wastewater containing chromium,copper,and sulfur.The details are as follows:First,the chemical reduction-alkali sedimentation process was used to treat high-concentration Cr（Ⅵ）passivation wastewater,and the influencing factors were systematically investigated.The experimental results show that the new liquid reducing agent can efficiently reduce Cr（Ⅵ）,and the free acidity,reaction time,the amount of reducing agent added,and the type of alkali have significant effects on the removal rate of Cr（Ⅵ）.When the volume concentration of the new reducing agent is3‰,the total acidity is 0.03mol/L,and the reaction time is 40min,the reduction rate of Cr（Ⅵ）in the wastewater can reach more than 99.5%.However,the use of lime milk to adjust alkali sedimentation can wrap Cu（Ⅱ）and Cr（Ⅲ）for adsorption and sedimentation,and will not cause precipitation alkali dissolution and Cr（Ⅲ）re-oxidation.Compared with barium salt precipitation method,ion resin exchange method and other commonly used reducing agents,it has certain advantages in terms of cost and process operation.Secondly,the Fenton-micro electrolytic sedimentation combined process was used to treat the high-concentration complexed heavy metal membrane washing wastewater,and the influencing factors were studied.The experimental results show that the first Fenton sedimentation can remove most of the COD_Cr,but the removal rate of copper and nickel ions is not high,suggesting that hydroxyl radicals preferentially remove free organics;the second Fenton sedimentation can break the Cu（Ⅱ）complex by adjusting the acid settlement.Ni（Ⅱ）has strong complexing ability in acidic environment,so the recapture agent is used to settle the complex in weak alkaline environment.The data show that the p H,time,and dosage of Fenton reaction reagent have a greater impact on the removal rate of pollutants,while the p H has a greater impact on the effect of the recapture reaction.This process removes heavy metals in a strong complex state at low cost,and can avoid the accumulation of pollutants in the process of reclaimed water reuse.Finally,the high-concentration ammonium sulfide wastewater is treated by aeration catalytic oxidation process.During the aeration,a large amount of S^2-escapes in the form of H₂S and is absorbed by the caustic soda solution,while the transition metal hydroxide can absorb more oxygen to increase the oxidation rate of sulfide ions.The absorbed H₂S can be further catalyzed and oxidized to S₂O₃^2-,and then oxidized to sulfate a second time,which can be directly incorporated into the current treatment system or treated by struvite method to discharge standards.Studies have shown that temperature has little effect on the sulfide ion oxidation rate within a certain range,while the aeration volume and catalyst have obvious effects.Compared with the iron salt precipitation method,this process does not produce secondary pollution,and there is no need to modify the current treatment process.