Adsorption And Electrochemical Regeneration Of Ammonia Nitrogen In Aquaculture Wastewater By Artificial Zeolite

Water is the source of life.Water pollution is an issue that people are increasingly concerned about,Water pollution includes industrial pollution and agricultural pollution.Aquaculture wastewater is one of the more serious pollution in agricultural pollution.The turbidity,chemical oxygen demand(COD),and ammonia nitrogen content of aquaculture wastewater are relatively high,resulting in eutrophication of the water and poisoning the fish in the water.Therefore,the treatment of aquaculture wastewater is very necessary.In this paper,flocculant polysilicate aluminum sulphate iron was synthesized from sodium silicate,aluminum sulfate and aluminum sulfate for the pretreatment of aquaculture wastewater.Then the optimal conditions and mechanism for the removal of ammonia nitrogen from wastewater by artificial zeolite were studied.The influencing factors of the electrochemical regeneration of man-made zeolites were discussed,and the performance of man-made zeolites for multiple adsorption regeneration was evaluated.Firstly,the synthesis conditions of the flocculant polyaluminum ferric sulfate aluminum sulfate was studied and the influence of pH value on the turbidity removal rate of the wastewater was investigated.The infrared spectroscopy(IR)and X-ray diffraction(XRD)results showed that the SO42-,Fe3+ and Al3+ in raw materials were all involved in the reaction,and they were complexed with polysilicic acid to form an amorphous polymer.Polymer.In addition,the synthesis condition of aluminum polysilicate ferric sulfate has a great influence on the flocculation process.The best conditions are n(Fe):n(Al)= 2,n(Fe+Al):n(Si)= 8 and the maturation time is 21 hours.When the dosage of flocculant was 30mL/L and the pH value of wastewater was 5,the flocculation effect was the best,and the removal rate of wastewater turbidity was as high as 91.86%.Then,artificially treated zeolite was used to treat the aquaculture wastewater after flocculation,and the best conditions for the removal of ammonia nitrogen from artificial zeolite were studied using ammonium chloride solution as simulated ammonia nitrogen wastewater.The results show that the removal rate of ammonia nitrogen from man-made zeolite overall appears first quick back slow trend,and the adsorption reaches equilibrium at 90 min.Because the adsorption of ammonia nitrogen by zeolite is an exothermic process,the removal rate of ammonia nitrogen decreases with the increase of temperature.When the acidic of wastewater is too strong or too weak,it is not conducive to the adsorption of ammonia nitrogen by the artificial zeolite.Because the H+ in the waste water will compete with the NH4+ when the acidity is too strong,and the ammonia nitrogen will exist in the form of NH3·H2O when the alkali is too strong.In addition,the optimal dosage of artificial zeolite is 120g/L.Under the optimal conditions,the removal rate of ammonia nitrogen in the culture wastewater from artificial zeolite can reach 80.12%.In addition,the adsorption kinetics,adsorption thermodynamics,and ion exchange processes of zeolites on ammonia nitrogen were studied.In terms of adsorption kinetics,the pseudo-first and pseudo-second kinetic models were used to simulate the adsorption process.The results show that the pseudo-second-order kinetics model can better describe the adsorption process of ammonia by zeolite.Then the adsorption process was further simulated using the internal diffusion kinetic model.The results show that the adsorption process of ammonia by zeolite is divided into three steps:liquid film diffusion,internal diffusion process and dynamic equilibrium.In the adsorption thermodynamics study,the Langmuir model,Freundlich model and Tempkin model were used for adsorption isotherm simulation.The results show that the Langmuir model and Freundlich model can better describe the adsorption equilibrium of ammonia by zeolite,and the thermodynamic study also shows that the zeolite on ammonia nitrogen adsorption is an exothermic process.Finally,ion exchange experimental studies show that the ion exchange process of ammonia nitrogen on zeolites is mainly exchanged with Na+,supplemented by the exchange of K+ and Ca2+,and Mg2+ is basically not involved in the exchange process.Finally,the lead oxide electrode was selected to study the influencing factors of the electrochemical regeneration of artificial zeolite,and the multiple adsorption regeneration performance of the man-made zeolite was evaluated.The optimum conditions of the regeneration experiment were verified by the response surface method.The results showed that with the increase of the electrolysis time,the regeneration effect of the artificial zeolite was improved.When the electrolysis time was 40 min,the adsorption and regeneration reached the equilibrium.The regeneration effect of the artificial zeolite was the best at pH of 10.Besides,the NaCl in the electrolyte acts as a conductor and generates chlorine or hypochlorous acid to oxidize ammonia during the electrolysis process,but when the concentration of Na+ is too high,it may have negative effect on the performance.Within the scope of this experiment,the optimum NaCl concentration is 0.1 mol/L.As the desorption of zeolite is an endothermic reaction,the regeneration rate of zeolite increases when the temperature rises.But when the temperature exceeds 50?,it will lead to a reduction in the regeneration rate of the zeolite.Under the optimal conditions above,the regeneration rate of zeolite can reach as high as 97.48%.After artificial zeolite was regenerated by six times of adsorption in the simulated ammonia nitrogen wastewater and actual aquaculture wastewater,the regeneration rate of the artificial zeolite reached more than 84%,indicating that the artificial zeolite has a good regeneration performance.