title: Effect of low molecular weight organic acids on phosphorus adsorption by ferric-alum water treatment residuals.
abstract: Effects of low molecular weight organic acids (LMWOAs; citric acid, oxalic acid and tartaric acid) on phosphorus (P) adsorption by ferric-alum water treatment residuals (FARs) were studied. Both batch and column experiments indicated that the effects of LMWOAs on P adsorption were closely related to adsorption time. Initially, all acids presented inhibitory function on P adsorption. The inhibition became weaker with time, eventually promoting P adsorption for citric acid and tartaric acid. In the column experiment with a 61-day duration, high P adsorption rates (>55%) were observed for the test groups containing citric acid and tartaric acid. Interestingly, higher pH likely enhanced P adsorption with the effects of LMWOAs and a distinct relationship between LMWOAs' effects on P adsorption and their concentrations was not observed. Moreover, fractionation of the adsorbed P from the FARs demonstrated that oxalic acid reduced P adsorption capacity, while citric acid and tartaric acid increased. Based on the forms of Fe and Al existing in the FARs and Fourier transform infrared spectroscopy analyses, LMWOAs can promote P adsorption through activating crystalline Fe/Al and preventing crystallization of amorphous Fe/Al to increase P adsorption sites, and can also inhibit P adsorption by competition with adsorption sites.
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, School of Environment, Beijing Normal University, Beijing, PR China.
authors.forename: Changhui
authors.initials: C
authors.lastname: Wang
authors.forename: Ziyuan
authors.initials: Z
authors.lastname: Wang
authors.forename: Lu
authors.initials: L
authors.lastname: Lin
authors.forename: Binghui
authors.initials: B
authors.lastname: Tian
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Pei
mesh_terms: D000143:Acids / Q000737:chemistry*; D000327:Adsorption; D000534:Alum Compounds / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D010758:Phosphorus / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000143:Acids; D000534:Alum Compounds; D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; D010758:Phosphorus