GLOBAL POLLUTION PROBLEMS, TRENDS IN DETECTION AND PROTECTION Alginate beads containing water treatment residuals for arsenic removal from water—formation and adsorption studies Daniel Ociński 1 & Irena Jacukowicz-Sobala 1 & Elżbieta Kociołek-Balawejder 1 Received: 30 January 2016 /Accepted: 26 April 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract Water treatment residuals (WTRs) produced in large quantities during deironing and demanganization of in- filtration 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 -1 for As(III) and As(V), respectively. At neutral pH, the adsorption effectiveness decreased to 3.3 mg As g -1 for arsenites and to 0.7 mg As g -1 for arsenates. The presence of carboxylic groups in polymer chains impeded in neutral conditions the diffusion of anions into sorbent beads; there- fore, 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. Keywords Calcium alginate . Arsenic adsorption . Water treatment residuals . Metal oxides . Hybrid polymer Introduction Arsenic is considered as one of the most toxic and carcino- genic naturally occurring contaminants of drinking water sup- plies. Since the long-term ingestion of water or food contain- ing even small quantities of arsenic causes a variety of dis- eases, in many countries, its maximum contaminant level in drinking water has been revised from 0.05 to 0.01 mg L -1 in accordance with WHO recommendations. The problem of elevated concentrations of arsenic compounds in water intended for human consumption concerns many regions of the world including rural areas in Bangladesh and India, some European countries, and the USA (Karagas et al. 2015). Therefore, development of efficient and cost-effective tech- nologies for arsenic removal from water is a subject of inten- sive research. Among different techniques used for this pur- pose the most promising is adsorption, which is highly valu- able for the removal of contaminants present in water at low concentrations, simultaneously enabling their reduction to sig- nificantly lower, recommended levels of several μgL -1 . For arsenic removal from water, different adsorbents have been used such as reactive polymers, activated carbon, and various biosorbents obtained from living or dead waste bio- mass (Mohan and Pittman 2007; Pandey et al. 2009). However, the most effective and selective toward arsenic spe- cies are adsorbents based on metal oxides including ferric oxides, aluminum oxides, manganese oxides, and cupric ox- ides (Giles et al. 2011; Hua et al. 2012; Manning et al. 2002; Responsible editor: Angeles Blanco * Daniel Ociński daniel.ocinski@ue.wroc.pl 1 Department of Industrial Chemistry, Wroclaw University of Economics, ul. Komandorska 118/120, 53-345 Wrocław, Poland Environ Sci Pollut Res DOI 10.1007/s11356-016-6768-0