Research On Resource Recovery Of Stainless Steel Hydrochloric Acid Wastewater

In this paper,the components in the stainless steel hydrochloric acid pickling wastewater are analyzed and determined.The acid concentration is 1.82mol/L,the fluoride ion content is 0.62mol/L,and the content of Fe2+,Fe3+,Ni2+ and Cr3+ are 0.7mol/L,0.1mol/L,0.002mol/L and 0.16mol/L.The traditional neutralization precipitation method to treat stainless steel pickling wastewater will produce high-salt wastewater,and the content of metal ions and fluoride ions is still high,which not only harms the environment,but also causes a waste of resources.Therefore,it is necessary to study an efficient,economical and green stainless steel pickling wastewater treatment process.In the process of measuring the acid concentration of stainless steel hydrochloric acid wastewater,if phenolphthalein is directly used as an indicator for acid-base titration,the non-ferrous metal ions in the wastewater will interfere with it.Therefore,through calculation,a new direct indicator method is established:Fe2+in the waste acid was used as an indicator,and sodium hydroxide solution was used for titration.The conical flask must be shaken constantly during the titration process.When the solution produces green Fe(OH)2 precipitation,and then quickly turns yellow-brown Fe(OH)3 precipitation,the end of the titration is reached.Combined with the standard recovery method,the relative error is 0.23%.This method has a wide application range and is suitable for the determination of acid concentration in many kinds of steel pickling wastewater.The simulation study of the separation of metal ions and acid is carried out by the acid retardation method.Explore the effects of changing the amount of peracid,the elution volume of distilled water,and the number of elutions on the adsorption and elution process of pressurized low-bed acid recovery resin columns with different height-to-diameter ratios.The following rules are drawn:The height-to-diameter ratio of the resin column is greater than 4/10 or less than 3/6,which is not conducive to resin adsorption and single elution rate;when the resin column is short and wide,the cumulative elution rate of the resin is the best;the Fe2+in the acid solution Existence will affect the acid recovery rate.The higher the Fe2+content,the lower the acid recovery rate and the better the separation effect of acid and metal ions.The resin column with a height-to-diameter ratio of 4/6 has the best single resin adsorption rate and elution rate.In the recycling process,using the optimal parameters of adsorption and elution obtained in the experiment,the resin elution rate can reach 100%,the acid recovery rate is more than 75%.The maximum separation rate of Fe2+ and acid is 88%.The stainless steel hydrochloric acid wastewater has been defluorinated,using the coordination effect of different defluorinating agents and fluorine to carry out defluorinating experiments under different conditions.As the molar ratio of silicon to fluorine in the solution,the reaction temperature,the reaction time and the amount of defluorination aid increase,the defluorination effect tends to increase first and then decrease.When the temperature is 30℃,the molar ratio of silicon to fluorine is 4:6,the defluorination time is 30min,and the defluorination aid is 2mL of saturated KCl,the gas phase method SiO2 has a better defluorination effect,and the defluorination rate is as high as 95.1%.Using the adsorption method to analyze the feasibility of Ni2+,Cr3+ adsorption and recovery,through the preparation of cellulose-chitosan membrane,explore the effect of changing the amount of adsorbent,adsorption time and solution pH on its adsorption performance.With the increase of the amount of adsorbent,the adsorption effect of Ni2+ and Cr3+ becomes worse.With the increase of adsorption time,the adsorption capacity of adsorbent gradually reaches saturation.Under acidic conditions,the adsorption effect of adsorbent on nickel and chromium ions is better.When the amount of adsorption material is 0.01g,the pH is 3,and the adsorption time is 8 hours,the cellulose-chitosan film has a better adsorption effect on nickel ions,and the adsorption amount reaches 67.2mg/g;when the amount of adsorption material is 0.05g,When the pH is 3 and the adsorption time is 6h,the cellulose-chitosan film has a better adsorption effect on chromium ions,and the adsorption capacity is 0.46mg/g.Through the step-by-step recovery experiment of stainless steel hydrochloric acid wastewater,the acid retardation method and the adsorption method cannot fully recover the acid and metal ions in the acid solution.Therefore,the resource recovery of pickling wastewater by the phosphoric acid distillation method is explored.The acid recovery rate of this method is 86%.The obtained distillation residue can be washed into the organic phase by adding ethanol to the remaining acid,water and organic additives to obtain almost Phosphate without water and acid.Combined with infrared spectroscopy analysis,most of the organic additives can be recovered.The separated phosphate is prepared by solid-phase method like lithium iron phosphate cathode material,combined with charge and discharge test,AC impedance analysis and cyclic voltammetry test,the phosphate formed by metal ions such as iron,chromium and nickel in the waste acid has The possibility of preparing lithium iron phosphate-like electrode materials.