title: Alginate beads containing water treatment residuals for arsenic removal from water-formation and adsorption studies.
abstract: Water treatment residuals (WTRs) produced in large quantities during deironing and demanganization of infiltration water, due to high content of iron and manganese oxides, exhibit excellent sorptive properties toward arsenate and arsenite. Nonetheless, since they consist of microparticles, their practical use as an adsorbent is limited by difficulties with separation from treated solutions. The aim of this study was entrapment of chemically pretreated WTR into calcium alginate polymer and examination of sorptive properties of the obtained composite sorbent toward As(III) and As(V). Different products were formed varying in WTR content as well as in density of alginate matrix. In order to determine the key parameters of the adsorption process, both equilibrium and kinetic studies were conducted. The best properties were exhibited by a sorbent containing 5 % residuals, formed in alginate solution with a concentration of 1 %. In slightly acidic conditions (pH 4.5), its maximum sorption capacity was 3.4 and 2.9 mg g-1for As(III) and As(V), respectively. At neutral pH, the adsorption effectiveness decreased to 3.3 mg As g-1for arsenites and to 0.7 mg As g-1for arsenates. The presence of carboxylic groups in polymer chains impeded in neutral conditions the diffusion of anions into sorbent beads; therefore, the main rate-limiting step of the adsorption, mainly in the case of arsenates, was intraparticle diffusion. The optimal condition for simultaneous removal of arsenates and arsenites from water by means of the obtained composite sorbent is slightly acidic pH, ensuring similar adsorption effectiveness for both arsenic species.
authors.affiliation: Department of Industrial Chemistry, Wroclaw University of Economics, ul. Komandorska 118/120, 53-345, Wrocław, Poland. daniel.ocinski@ue.wroc.pl.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ociński
authors.affiliation: Department of Industrial Chemistry, Wroclaw University of Economics, ul. Komandorska 118/120, 53-345, Wrocław, Poland.
authors.forename: Irena
authors.initials: I
authors.lastname: Jacukowicz-Sobala
authors.affiliation: Department of Industrial Chemistry, Wroclaw University of Economics, ul. Komandorska 118/120, 53-345, Wrocław, Poland.
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Kociołek-Balawejder
mesh_terms: D000327:Adsorption; D000464:Alginates / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry* / Q000302:isolation & purification; D005618:Fresh Water / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D017895:Manganese Compounds / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000302:isolation & purification; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*; D014881:Water Supply
chemical_list: D000464:Alginates; D017895:Manganese Compounds; D010087:Oxides; D014874:Water Pollutants, Chemical; C027424:manganese oxide; D007501:Iron; D001151:Arsenic
keywords: Arsenic adsorption; Calcium alginate; Hybrid polymer; Metal oxides; Water treatment residuals