Comparison of Removal Efficiency of Phosphorus and Ammonium in Solutions by Five Substrates

Both phosphorus(P) and ammonium(NH+4-N) adsorption capacities of fly ash,alumina,activated carbon,burnt stone and vermiculite with physical and chemical characteristics were examined for the potential use as substrate in removing P and N in polluted water.Results showed that: Among the 5 substrates,fly ash was alkaline with the highest Fe,Ca and active Fe,Ca contents,while alumina was acid with highest Al and active Al contents.There was 21.6% of Mg found in vermiculite.Activated carbon had the largest specific area.Adsorption characteristics of P and NH+4-N by these 5 substrates were well fitted by Langmuir adsorption isotherms.The highest P adsorption capacity was found in fly ash with 10.37 mg/g,and the highest NH+4-N adsorption capacity was noted in vermiculite with 7.1 mg/g.In P combined with NH+4-N solutions,the P or NH+4-N adsorption capacity of all substrates were lower than those in P or NH+4-N solutions.Fly ash,with high adsorption capacity both in P and NH+4-N,was recommend as an ideal substrate in removing P and N in polluted water.