Study On The Adsorption Of Low Concentration Ammonia Nitrogen By Vermiculite And Adsorption Of Low Concentration Humic Acid By Palygorskite

The pollution of groundwater has become a serious problem which was concerned in recent years.Ammonia nitrogen（NH₃-N） and humic acid（HA） have become the main contaminants of water and have great influence on the living of human beings.Many researchers have studied on the removal of pollutants from groundwater.Permeable reactive barrier（PRB） is a kind of technology for the in situ removal of groundwater contaminants,which have the advantage of sustainability and economic practicality.The material of PRB is an important part of the study.Natural mineral materials have become the ideal materials in the removal of water contaminants because of inexpensive,accessible,no secondary pollution.In this paper,in order to remove the low concentration of ammonia nitrogen and low concentration of humic acid of groundwater in Shenyang,vermiculite and polygorskite are selected as active materials.In this paper,the X-ray diffraction of vermiculite,the cation exchange capacity, the maximum adsorption of ammonia nitrogen and permeability were measured.The effects of vermiculite adsorption time,particle size,the dosage of vermiculite,pH and temperature on the adsorption of NH₃-N at low concentrations were investigated. According to measure the X-ray diffraction,TG-DTA and FTIR analyses of the raw vermiculite and NH₃-N adsorbed vermiculite,and the change in cation concentrations in the solution,the adsorption mechanism was discussed.In this paper,the X-ray diffraction of ploygorskite,the scanning electron microscope,surface area,the maximum adsorption of HA and permeability were measured.The effects of ploygorskite adsorption time,particle size,the dosage of ploygorskite,pH,ion strength,temperature on the adsorption of HA at low concentrations were investigated.According to measure the X-ray diffraction, TG-DTA and FIIR analyses of the raw ploygorskite and HA adsorbed ploygorskite, the adsorption mechanism was discussed.The results of adsorption of NH₃-N by vermiculite show that the cation exchange capacity of vermiculite was 0.9mmol/g.The sorption capacity of NH₃-N on vermiculite with a particle size of 1.5mm was 18mg/g after 5 hours of equilibration and fitted the Langmuir adsorption better.The optimal sorption was at pH 6-7 and 60℃,which is different from that of at high NH₃-N concentrations.The smaller the particle size of vermiculite,the more the NH₃-N adsorbed.As the dosage of vermiculite increased,the removal of NH₃-N was from 10mg/L to 1.1mg/L.The X-ray diffraction,DTA-TG,and FTIR analyses of the raw vermiculite and NH₃-N adsorbed vermiculite,and the change in cation concentrations in the solution indicated that cation exchange was the mechanism for NH₃-N uptake from low concentration solution.The results of adsorption of HA by polygorskite show that the maximum adsorption of HA on palygorskite was 17mg/g at 20℃and 0.074 mm,the adsorption equilibrium time was 2h at pH 6-7 and fitted pseudo-second-order sorption models. The sorption of HA on palygorskite increased at low pH,high ion strength and smaller particle sizes.As the dosage of palygorskite increased,the removal of HA was from 20mg/L to 2.6 mg/L.The X-ray diffraction,DTA-TG,and FTIR analyses of the raw palygorskite and HA adsorbed palygorskite indicated that electrostatic interaction was the mechanism for HA uptake from low concentration solution.