Adsorption Of Phenol By Alum Sludge From Waterworks

Alum sludge is a by-product of drinking water treatment processes,which is formed as a result of addition of aluminum or iron salts to raw water to remove a veriety of inpurities/contaminants.Phenol is one of the hardly degradable organics,having high toxicity and being widely used in industry.Till now,alum sludge has been proved with ability to adsorb many pollutants such as phosphorus,nitrogen,and some heavy metals,but studies on its efficiency in adsorbing phenol are still lacking.In this study,the main purpose is reusing the alum sludge to remove phenol from the waste water.Through static and dynamic experiments combined analyzing the composition and structure of alum sludge,the capability of alum sludge for adsorbing phenol was evaluated.The major results achieved are listed below.The mineral composition,surface micro topography characteristics,surface oxygen-containing functional groups and other physicochemical properties of alum sludge were analysed by using SEM、XRF、XRD and FTIR methods,respectively.The results showed that the surface of sludge is rough and porous,the mian composition includes SiO2,Al2O3,and Fe2O3,the main functional group is hydroxyl（-OH）,and the specific surface area of alum sludge is 10.623 m²·g^-1obtained by BET method.The static adsorption test reveals that the alum sludge can effectively immobilize phenol and the removal rate was over 99%in the following conditions:1)the initial concentration of phenol is 100mg/L;2)particle size of alum sludge is under 0.075mm;3)the dosage of sludge is 1.8g and 4)the pH is 8.The batch equilibrium data fitted well to the Langmuir and Freundlich than to Timkin and D-R isotherms.The maximum adsorption capacity of alum sludge for phenol is 18.21mg/g.Based on dynamic adsorption tests,the effects of initial phenol concentration and flow rate were explored.The experimental results showed that the breakthrough time was 120 days under the condition of 100 mg/L phenol concentration and flow rate of0.06 mL/min.When the initial phenol concentration is 500 mg/L,the Thomas and Yoon-Nelson models were both fitted well for the adsorption of phenol（R²=0.92）.By comparing the SEM,XRF,XRD and FTIR results of alum sludge before and after adsorption,it can be concluded that the phenol adsorption on alum sludge was mainly a physical adsorption.The supposed adsorption mechanism was showed in a diagram.