Study On Removal Of Phosphorus In Wastewater With Red Soil In Southern District

Eutrophication is a serious pollution problem our society are facing. Most researchsindicated the dominant factor of eutrophication is phosphorus.As the national importantmineral resources,the application of clay minerals for phosphorus removal in wastewateris becoming the focus of pollution prevetion against phosphorus in recent years,anddeveloping a sort of clay mineral adsorption which is efficient,safe and cheap is the keyof this technique.In this article we applied the red soil distributed in most areas insouthern China to studies on phosphorus removal effect and mechanism,in order to finda new sort promising adsorbent for phosphorus removal.There are some studies on influencing factor, thermodynamics and kinetics forphosphorus removal by red soil,purified red soil and the modified, evaluating the actualapplication and feasibility of phosphorus removal by all sorts of red soil.The results areas follows:The content of Al2O3is key to phosphorus removal for clay minerals by quantifyingchemical composition,while both Al2O3and Fe2O3in red soil are beneficial to theadsorption of phosphorus. Red soil is more effective to phosphorus removal than otherminerals.The adsorption on red soil in two hours in the two simulated phosphoruswastewater is1.7times more than other minerals at least,with the removal rateincreasing more than34.4percentage.The purification can improve the effect ofphosphorus removal on red soil,with the adsorption increased by9.6percentage. Theadvantage of purification is more remarkable under higher pH value or less dosequantity condition.Red soil is able to adapt to the wide range of pH value in thesolution,and the value of effluent varies from4.72to7.79.Both modified red soil by hydrochloride and soil by heated can increase theadsorption capacity,yet heating process is better than hydrochloridetechnique,especially in the simplicity and in removal effect.The larger concentration ofacid may lower the adsorption capacity.In the simulated wastewater with initialconcentration of35mg/L,the effluent concentration of phosphorus on modified red soilby heating for2hours at200degree Celsius is below0.5mg/L in two hours,whichreaches level1standard of the comprehensive emission standard;it can also get a goodeffect in the simulated wastewater with initial concentration of50mg/L.The modified red soil by heating has more potential in the adsorption quantity increase than themodified after purified.Red soil and the modified soil fitted best to Langmuir isotherms equation, thepurification leads to greater removal effects in the solution with higher initialconcentrations of phosphorus.The fitting results show that modified red soil is suitablefor Feundlich isotherms equation because of mechanism change on phosphorusadsorption,and more molecular absorption phenomenon seems to appear.The kineticscharacteristics for red soil and the modified is the most suitable for the pseudo second-orderkinetics.The thermodynamic datas of both red soil and the modified soil indicates theadsorption reaction of phosphorus is endothermic,entropy increased andspontaneous.The modified soil by heating is sensitive to the variation of temperature.Red soil and the modified soil can be used to remove the concentrations ofphosphate,total phosphorus and COD in wastewater from livestock farm,rather thanammonia nitrogen and nitrate.Only one time treatment can’t reach the comprehensiveemission standard,in practice there need to be some assistant processes or many timestreatments.After the treatments all kinds of red soil can be produced to compoundfertilizer for farm improvment.The conclution shows that red soil and the modified is a new sort of phosphorusadsorbent with good prospects.