Study On Removal And Recovery Of Chormium In Tannery Wasterwater

China is a major country in leather production.The annual discharge of tannery wastewater reaches 2×10⁸ t,and the average chromium content in tannery wastewater is over 30 mg/L,far greater than the discharge standard of wastewater.With the raising of the concept of"zero discharge"and the gradual improvement of environmental regulations,the reuse of chromium-containing wastewater has become a major problem that must be solved in the construction of ecological civilization and sustainable development in leather industry.Therefore,it is of great significance to utilization of chromium from chromium-containing wastewater and protection of the environment.The study on the utilization of chromium from chromium-containing wastewater by using the combined technology of heavy metal capture agent and flocculants.This experiment mainly investigates the effect of capture agent type,dosage,pH value,temperature,the dosage of PAM,the coagulant dosage,and the sedimentation time on the removal efficiency of chromium from chromium-containing wastewater.The experiment shows that the capture agent of LX-Y803 had the best removal efficiency when the pH was 9,the reaction temperature was 50?,added 90 mg/L capture agent,and reaction for 15 minutes.And then added PAM and PAC,the dosage of addition was 2.5 mg/L and 0.2 mg/L,filtered after a certain time.The total chromium dechroming rate of tanning wastewater reached 98.27%,the total chromium concentration in the wastewater was reduced from 56.14 mg/L to 0.97 mg/L,reached the standards of discharging standard of water pollutants for leather and fur making industry?GB30486-2013?.The total chromium content in the chromium mud is53778.5 mg/kg,and the chromium mainly in the form of Fe-Mn oxides binding state and organic binding state.The chromium of dissolved state in the wastewater was removed first when precipitated chromium by heavy metal capture agent.The study on the utilization of chromium from high concentration chromium-containing wastewater by using the combined technology of heavy metal capture agent and flocculants.This experiment mainly investigates the effect of pH,capture agent type and dosage,temperature,and flocculant dosage on the removal efficiency of chromium from high concentration chromium-containing wastewater.The experiment shows that the capture agent of RS-200 had the best removal efficiency when the pH was 9,the reaction temperature was 90?,added 400 mg/L capture agent,after reaction for 30 minutes.And then added PAM and PAC,the dosage of addition was 3 mg/L and 1 mg/L,filtered after a certain time.The total removal rate of chromium reached 81.42%,the total chromium concentration in the wastewater was reduced from 359.7 mg/L to 62.25 mg/L.The total chromium content in the chromium mud is 34468.98 mg/kg,and the chromium mainly in the form of Fe-Mn oxides binding state and organic binding state.The concentrated chromium wastewater,which is not competely removal,could be continue concentrated in the membrane device.The chemical reaction was carried out with heavy metal capture agent LX-Y803,Rs-200 and Cr?III?,?RS-200?-Cr and?LX-Y803?-Cr were obtained,and detection and analysis by infrared,SEM,EDS and TG.Rs-200 and Cr?III?have a chemical reaction to form a more stable composition,and the molecular formula might is(C₁₀₀N₁₄O₅S₂₀Cr₂₁)·30H₂O.LX-Y803 belongs to the inorganic heavy metal capture agent.The principle of complexation is the reaction of S^2-with Cr?III?,and the stable Cr₂S₃ is obtained.The effect of the concentration of sulfuric acid,the amount of addition,the temperature and the reaction time on the leaching efficiency of chromium in the chromium mud was studied.The optimum leaching temperature of tannery chromic sludge is 45?,added 6 mol/L sulfuric acid at the solid-liquid ratio was 1:20,and reacted 30 min,the rate of acid leaching reached 95.18%.The optimum leaching temperature of chromic sludge precipitated by concentrated chromium solution is60?,added 4 mol/L sulfuric acid at the solid-liquid ratio was 1:20,and reacted 60min,the rate of acid leaching reached 90.49%.The two groups of leaching solution was adjusted pH to 9 through sodium hydroxide solution to obtain the chromium powder,which the content of the power was 13.1%and11.4%,respectively.The process of the combined use of removing chromium by heavy metal capture agent and recovering chromium by acid leaching is a good application in the recycling of chromium-containing wastewater.