Study Of Removing Ammonia Nitrogen With Natural And Modified Zeolite From Water

In recent years,the water pollution incidents have occurred and those incidents which arecaused by the ammonia wastewater. Therefore,the treatment of ammonia wastewater hasbecome an important task.The research object of this test is the treatment of simulated ammonia wastewater.This testwhich chooses the zeolites of baiyin as adsorbent material is a static shock absorption test.Thenatural zeolites are characterized by Scanning Electron Microscopy(SEM) and EnergyDispersive Spectroscopy(EDS). The Cation Exchange Capacity (CEC) of the natural andNaCl modified zeolites are also determined. The modified zeolites are prepared by heatingcalcination,acid modified and NaCl modified methods and the suitable modified method andconditions are determined.Such as particle size,reaction temperature,shaking time,pH,zeolitedosage,coexisting substance, and initial concentration of ammonia, Those different factors,areanalysised for the natural and NaCl modified zeolites removaling ammonia nitrogen inwater.According to the ammonia adsorption properties of natural and NaCl modifiedzeolites,The Langmuir and Freundlich isotherm are draw for the ammonia adsorption ofnatural and NaCl modified zeolites.The thermodynamics and kinetics are alsostudied. Theresults are as follows:(1) The SEM pictures shows the rough surface and developed cavities structure of naturalzeolites; According to BET and EDS,the specific surface area are measured about9.29m2/g.The Al and Fe contentare11.36%and14.55%. Using a pH meter indicating potentiometrictitration,The cation exchange capacity of natural and NaCl modified zeolites are measuredabout80mmo1/100g and87.5mmo1/100g.(2)Those methods about high temperature calcination modified,acid (HCl,H2SO4) modifiedand NaOH modified are not suitable for modifying the natural zeolites of baiyin; while NaClmodified can significantly improve the performance of ammonia adsorption capacity; Theorthogonal experimental analysis shows that NaCl concentration is the main modified factor,followed by solid-liquid ratio,modified time, modified temperature;The optimal conditions ofNaCl modified zeolites are about NaCl solution at a concentration of8%, modified time6h,solid-liquid ratio of4g/100mL, modified temperature35℃.(3) The factors about the zeolite size,reaction temperature, time,pH,coexisting substances,ammonia initial concentration,zeolite dosage are analysised as followed: Within the particlesize range of6to30mesh, the particle size is smaller and the absorption is better; if the sizeis greater than30mesh and it trends gentle;The initial ammonia concentration is higher andthe adsorption capacity of natural and modified zeolites is greater,but to flatten in the end;Themaximum adsorption amount of NaCl modified and natural zeolites is up to10.11mg/g and 8.1mg/g, it improves2.01mg/g;Whether the natural zeolites or modified zeolites,the overimprovement dosage can’t raise the ammonia removal,therefore;In order to avoid unnecessarywaste, the dosage must be to determine correctly;The ammonia adsorption of natural andmodified zeolites has the feature about " rapid adsorption, slow post-balance",The ammoniaadsorption equilibrium time of natural and modified zeolites was about90min and180min;The suitable pH range for the ammonia adsorption of natural and NaCl modified zeolites isabout4-9and4-8;The reaction temperature to adsorption effect from25℃to35℃is notvery different;The effect of coexist substances with chlorine cation is: K+>Na+>Ca2+and theeffect coexistsubstances with sodium anion is:SO42->NO3->Cl->H2PO4-.(4) The correlation coefficient of Langmuir adsorption isotherm was higher than theFreundlich adsorption isotherm,indicating that the adsorption is basically a monolayeradsorption;The adsorption process is an endothermic reaction;The second-order kinetic model(R2=0.99)is better than the first-order kinetic(R2=0.96) to describe the dynamic behavior ofammonia adsorption of zeolite;The process is not just controlled by the inter-particlediffusion adsorption process but multi-step control.