The Adsorption Properties And Surface Charge Characteristics Of Zeolite/hydrous Metal Oxide Composite Synthesized From Coal Fly Ash

Zeolites are aluminosilicate minerals with many excellent properties such as high adsorption capacity and high stability because of zeolites'special stuctures.Use of coal fly ash?CFA?as raw material to synthesize zeolite?ZFA?is a good way to recycle waste solid.Although the preparation and application of ZFA had been intensively investigated to recycle the solid waste,problems arising from limited adsorption capacity of ZFA for some targeted pollutants and the waste alkaline solution remain due to the use of large amount of alkaline solution during the synthesis process.We have recently initiated a novel method to synthesize ZFA/hydrous metal oxide hybrid material by introducing a reaction step involving the neutralizing of the waste alkaline solution with soluble metal salts into the traditional ZFA synthesis route.We studied the electric charge characteristics of those two ZFA/hydrous metal oxide materials:zeolite/ferrihydrite?ZFA/HIO?and zeolite/zirconium oxide?ZFA/HZ?and their adsorption capaticy.We found that the newly developed material had higher cation exchange capacity,specific surface area and phosphate immobilization capacity than corresponding ZFA.In the research of ZFA/HIO and ZFA/HZ as adsorbents to remove methylene blue?MB?,the maxium adsorption capacity of MB at pH=11.0 were 156.25mg/g and 222.76mg/g for ZFA/HIO and ZFA/HZ respectively,which were much larger than ZFA?79.36 mg/g?.The adsorption capacity increased with the rise of pH values and the dosage of the adsorbent.Also,ZFA/HZ showed a great capacity for the removal of phosphate.The Langmuir maximum phosphate adsorption capacity of ZFA/HZ was22.62mg/g.The adsorption of phosphate by ZFA/HZ decreased with the increase of pH,and the common coexisting anions of Cl^-and NO₃^-in water had no obvious effect on its adsorption while HCO₃^-reduced the adsorption significantly via elevating pH value.