Study On Modified Ultra-fine Coal Fly Ash And Its Adsorption Capacity

The coal fly ash was a particle poss some activation, its also had some absorption capacity.The utilization rate of coal fly ash to treat wastewater was increased in recent years, we have achieved some achievements during the course of utilization of coal fly ash, the utilization of coal fly ash to treat wastewater have engendered a recycle of making use of waste to dispose waste.Because of the limitation of absorption, the coal fly ash should have to be modified to improve its absorption.In this paper, coal fly ashes obtained from Xijiao and Baqiao thermoelectricity plants were ultra-fined and then modified by alkali and microwave irradiation, which would improve the adsorption capacity.The adsorption capacity of methyl orange and chromium (VI) from aqueous solution were determined by reaction time, temperature, pH, dosage of adsorbent. Reprocess test of absorbent is also researched. The main achievements were as followed:(1) By contrast with the adsorption capacity of methyl orange and chromium (VI) from aqueous solution on raw coal fly ash and ultra-fine coal fly ash, it showed that ultra-fine coal fly ash had better adsorption capacity, and the Baqiao coal fly ash which was smaller in size had better adsorption capacity, so the adsorption capacity of coal fly ash was greatly relied on its diameter and specific surface area, the coal fly ash which was smaller in size had better adsorption capacity.(2) Optimum adsorption condition of methyl orange from aqueous solution on modified coal fly ash was obtained. For alkali-modified coal fly ash: the dosage of adsorbent was 0.5g, the concentration of methyl orange was 100mg/l,the volume of the solution was 50ml, pH of adsorption was 5, the reaction time was 120 minutes, the temperature was 25℃, the adsorption capacity was 6.93mg/g and 6.23mg/g respectively. For microwave irradiation modified coal fly ash: the dosage of adsorbent was 0.5g, the concentration of methyl orange was 100mg/l,the volume of the solution was 50ml, pH of adsorption was 6, the reaction time was 90 minutes, the temperature was 25℃, the adsorption capacity was 7.82mg/g and 7.17mg/g respectively.(3) Optimum adsorption condition of chromium (VI) from aqueous solution on modified coal fly ash was obtained. For alkali-modified coal fly ash: the dosage of adsorbent was 1.5g, the concentration of chromium(VI) solution was 100mg/l,the volume of the solution was 50ml, pH of adsorption was 6, the reaction time was 90 minutes, the temperature was 25℃, the adsorption capacity was 4.60mg/g and 4.44mg/g respectively;For microwave irradiation modified coal fly ash: the dosage of adsorbent was 0.7g, the concentration of chromium(VI) solution was 100mg/l,the volume of the solution was 50ml, pH of adsorption was 8, the reaction time was 60 minutes, the temperature was 25℃, the adsorption capacity was 3.88mg/g and 3.61mg/g respectively.(4) The adsorption isotherm model, kinetics model and thermodynamic parameters of methyl orange and chromium(VI) from aqueous solution on raw coal fly ash, ultra-fined coal fly ash and modified coal fly ash were studied. The result showed that adsorption of methyl orange fitted Frendlich isotherm model, adsorption of chromium(VI) fitted Langmuir isotherm model;the adsorption process of methyl orange and chromium(VI) from aqueous solution conform to the second-order kinetic model; the adsorption process of methyl orange and chromium(VI) from aqueous solution were proved to be exothermic.(5) The absorbent that has been used can be regenerated, and the regenerated one has good performance in the adsorption also.The adsorption experiment result showed that the optimum regeneration condition was ultrasonic power 160W, ultrasonic time 20min, the adsorption capacity on methyl orange was 4.33mg/g and 4.03mg/g respectively, the adsorption capacity on chromium(VI) was 3.06mg/g and 2.91mg/g respectively.