Study On Phosphorus Removal Characteristics Of Three Kinds Of Adsorbents Chemically Enhanced By Iron Salt

Eggshell,clinoptilolite and fly ash were selected as adsorbents to remove phosphorus from wastewater which was modified by iron salt.The adsorption kinetics,thermodynamic and adsorption isotherm model are used to investigate the adsorption characteristics and mechanisms of these three materials.The influence of original concentration of phosphorus,pH,particle size and dosage are studied,which can provide theoretical basis of similar experiments.The results as follows:(1)The phosphate ions can be adsorbed by original eggshell,zeolite and fly ash,the removal rate of these materials is namely 33%,37%,19.3%.The effects of various factors on the adsorption of natural materials were analyzed by single factor experiments,the result shows:the removal rate of original eggshell,zeolite and fly ash increase with the phosphorus concentration.Effect of pH on phosphorus removal efficiency is the most significant.Weak alkalinity conducive to natural eggshell adsorption,but the natural zeolite and fly ash are suitable for neutrality.The smaller natural particle size,the higher the adsorption capacity.With the increase of natural adsorbent dosage,the removal rate of phosphorus was increased,but the adsorption capacity was reduced.(2)The adsorption performance of modified eggshell is the best when the concentration of FeCl3 is 0.3%.Pseudo-sencond order kinetics and Freundlich were fitted to describe the process of phosphorus of eggshell.The "fast adsorption and slow equilibrium" characteristics of adsorption process was conformed to the modified eggshell,which reaction process is spontaneous endothermic.(3)The phosphorus removal efficiency reached 93.93%when the concentration of FeCl3 solution was 0.5%.The adsorption effect is less affected by temperature and particle size,which is greatly influenced by pH and dosage.The adsorption capacity was 4.9mg/g When pH=6,the dosage is 1g/100mL under the condition of 45 C.Phosphorus adsorption was good fitting to Langmuir and Freundlich,R2>0.99,which shows that the adsorption process occurs to heterogeneous layer.Physical adsorption dominates the adsorption process when?H=13.19KJ/mo<20KJ/mol.(4)The adsorption effect of modified fly ash is greatly affected by initial phosphorus concentration,pH and dosage.Natural fly ash has better adsorption effect under alkaline condition,while modified fly ash is suitable for neutral condition.After modification,the phosphorus removal efficiency of fly ash increased from 37%to 77.97%,and the adsorption capacity increased from 0.98 mg/g to 2.32 mg/g,When the temperature is 25? and the dosage is 1g/100mL.After modification,the adsorption effect of high concentration sewage is not good.(5)The dynamic experimental results show that:under the condition of the flow rate was 5 mL/min and the dosage was 10cm,the breakthrough time of eggshell was 4h,zeolite was 1.5h,and the composite fillers brokenthrough time was 5h.