Adsorption Of Phosphorus From Aqueous Solution By Natural And Modified Adsorbents

In recent years,because of excessive emissions of nutrients in the water such as nitrogen and phosphorus,algal blooms and red tides in varying degrees have occurred in many rivers,lakes and oceans in our country.In view of the increasingly serious problem of water eutrophication,this paper used natural heulandite,faujasite,volcanic stone and medical stone in Lingshou of Hebei province as adsorbent,and chosed the four methods such as roasting,impregnants of NaOH,AlCl₃ and FeCl₃ to modify the four natural ores.The adsorption effect of natural and modified adsorbent on phosphate in wastewater was investigated in the paper,choose the best adsorbent and modification method,optimize the modified conditions by the single factor and orthogonal experiments,and compared the phosphate adsorption capacity of natural and modified adsorbent by static adsorption experiment.Structures of the natural and modified adsorbent were characterized by SEM,XRD,BET,XRF and FTIR.The phosphorus removal mechanism was analyzed by adsorption isotherm,adsorption thermodynamics and kinetic model.The phosphate saturated modified adsorbent was regenerated by different regeneration methods.Then treated the simulated wastewater with phosphorus by dynamic adsorption test.The research results are as follows:1)The adsorption capacity of phosphate in wastewater was significantly different after natural heulandite,faujasite,volcanic stone and medical stone were modified by different methods,and the phosphate removal effect of faujasite modified by FeCl₃ solution was the best.2)The optimal modification conditions of faujasite modified by FeCl₃ solution:the particle size of faujasite was 30⁵0 mesh,the concentration of FeCl₃ solution was 1mol/L,the modification time was 6h,the modified and drying temperature was 25?and 80?,respectively,and the modified dosage was 800 g/L.The order of four influential factors on the effect of modification:concentration of FeCl₃ solution>reaction time>reaction temperature>drying temperature.3)The removal rate of phosphate by faujasite was improved significantly after modification by FeCl₃ solution.When the dosage was 50 g/L,the reaction time was 8h,the temperature was 25?,pH value was 4⁹,and the initial concentration of phosphate was 50mg/L,the removal rates of natural and modified faujasite were 24.30%and 99.26%,respectively.The order of four influential factors on the adsorption efficiency of modified faujasite:dosage>reaction temperature>reaction time>pH.4)The crystal structure of faujasite did not change significantly after the modification of faujasite.However,the content of Si and Fe increased,and Fe₂O₃·H₂O adhered to faujasite surface.Anionic adsorption of faujasite was more apt to electrostatic attraction.It also blocks the pore structure,and reduces the specific surface area,pore size and pore volume.5)The temperature of 288³18K,the Langmuir and Freundlich model could well described the adsorption process of phosphate by modified faujasite,the maximum adsorption capacity was 5.21mg/g.The thermodynamic parameters show that the adsorption of phosphate by modified faujasite was spontaneously endothermic reaction.The pseudo-second-order kinetics were useful since the adsorption rate data fitted well.6)The optimal regeneration methods for phosphate saturated faujasite was FeCl₃solution.The removal rate of phosphorus in wastewater can still reach 94.6%after nine times of repeated regeneration.In dynamic adsorption experiment,the adsorption equilibrium of natural and modified faujasite for phosphate taked 47h and 90h,respectively.