title: Effect of pH on the coagulation performance of Al-based coagulants and residual aluminum speciation during the treatment of humic acid-kaolin synthetic water.
abstract: The fractionation and measurement of residual aluminum was conducted during the treatment of humic (HA)-kaolin synthetic water with Al(2)(SO(4))(3), AlCl(3) and polyaluminum chloride (PAC) in order to investigate the effect of pH on the coagulation performance as well as residual aluminum speciation. Experimental results suggested that turbidity removal performance varied according to the following order: AlCl(3)>PAC>Al(2)(SO(4))(3). HA removal performance of PAC was better than that of AlCl(3) under acidic condition. The optimum pH range for AlCl(3) and Al(2)(SO(4))(3) was between 6.0 and 7.0 while PAC showed stable HA and UV(254) removal capacity with broader pH variation (5.0-8.0). For the three coagulants, majority of residual aluminum existed in the form of total dissolved Al (60-80%), which existed mostly in oligomers or complexes formed between Al and natural organic matter or polymeric colloidal materials. PAC exhibited the least concentration for each kind of residual aluminum species as well as their percentage in total residual aluminum, followed by AlCl(3) and Al(2)(SO(4))(3) (in increasing order). Moreover, PAC could effectively reduce the concentration of dissolved monomeric Al and its residual aluminum ratio was the least among the three coagulants and varied little at an initial pH between 7.0 and 9.0.
authors.affiliation: Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Ji'nan 250100, China.
authors.forename: Zhong Lian
authors.initials: ZL
authors.lastname: Yang
authors.forename: Bao Yu
authors.initials: BY
authors.lastname: Gao
authors.forename: Qin Yan
authors.initials: QY
authors.lastname: Yue
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000534:Alum Compounds / Q000737:chemistry; D000535:Aluminum / Q000737:chemistry*; D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007616:Kaolin / Q000737:chemistry*; D016014:Linear Models; D013056:Spectrophotometry, Ultraviolet; D018508:Water Purification / Q000379:methods*
chemical_list: D000534:Alum Compounds; D017607:Aluminum Compounds; D002712:Chlorides; D006812:Humic Substances; D007616:Kaolin; C041524:aluminum sulfate; D000077410:Aluminum Chloride; D000535:Aluminum