Study On The Compound Modification Of Natural Mineral Adsorbents To Remove Nitrogen And Phosphorus

Excessive nitrogen and phosphorus are the key causes of water quality deterioration.A large amount of wastewater containing nitrogen and phosphorus in production and life is discharged into natural water,which not only causes serious pollution,but also poses a great threat to human health and sustainable development.Natural mineral materials are abundant in source,with unique crystal structure,large specific surface area,good ion exchange and adsorption performance,which have certain removal effect on on nitrogen and phosphorus,but the restricted adsorption amount limits their application in water pollution treatment.In this paper,the denitrification and dephosphorization effects of natural mineral materials widely existed in nature were enhanced by thermal modification and thermal/chemical composite modification.The main contents and conclusions are as follows:?1?Through the nitrogen and phosphorus release amount experiments and the adsorption experiment of seven natural mineral materials,such as zeolite,plagioclase zeolite,kaolinite,montmorillonite,quartz sand,volcanic stone and medical stone.Zeolite and kaolinite were selected as the best raw materials for removing ammonia nitrogen and total phosphorus respectively.?2?Research results show that the adsorption process of ammonia nitrogen by zeolite is rapid.However,the equilibrium process is slow.The adsorption process accords with pseudo-second order model and has a high fitting degree with the Langmuir isotherm adsorption model.The maximum adsorption capacity is 1.32 mg/g.The adsorption process of PO₄^3-by kaolinite accords with pseudo-first order kinetic model.The Freundlich isotherm adsorption model has better matching effect,this indicates that PO₄^3-was chemically adsorbed by kaolinite and the adsorption reaction was spontaneous.?3?The thermal modification treatment has an effects on removing interlayer impurities of zeolite and kaolinite material,dredging the channels,increasing the specific surface area and the pore diameter.After thermal modification of zeolite at 200?for four hours,the adsorbing capacity to ammonia nitrogen reached 1.32 mg/g.After the natural kaolinite was thermally modified at 400?for one hour,the adsorption amount of PO₄^3-reached 0.63mg/g.?4?The results of composite modification of zeolite with sodium chloride and sodium citrate showed that the effect of sodium citrate was better than that of sodium chloride,the adsorption amount of ammonia nitrogen was 2.50 mg/g.The composite modification of natural kaolinite by aluminum chloride and ferric chloride showed that the modified effect of ferric chloride was poor,and the adsorption capacity of kaolinite on phosphate ions reached 0.76mg/g after the composite modification of aluminum chloride with the concentration of 0.05mol/l.