Starch as novel water soluble biopolymer in removal mixtures heavy metal ions via polymer enhanced ultrafiltration

Abstract

Four heavy metals Zn (II), Pb (II), Cr (III) and Cr (VI) were selected in this work was tested through a Polymer Enhanced Ultrafiltration (PEUF) system. The effects of pH, polymer concentration and metal ions feed concentration were the main focus and influenced the performance of PEUF system. A conventional water-soluble polymers was selected, namely polyethylene glycol (PEG), and an unmodified starch as biopolymer is proposed as an alternative binding reagent for four selected metal ions used for heavy metals removal from wastewater. Speciation profiles of Zn (II), Pb (II), Cr (III) and Cr (VI) species were obtained using available software to identify the soluble complexes of Zn (II), Pb (II),Cr (III) and Cr (VI) ions and hydroxides ions (OH-) present in various charged ions, either as anions or cations, at certain pH range. Investigation through experimental works was done using ultrafiltration systems obtained by laboratory ultrafiltration bench scale equipped with 10 kDa polysulfone hollow fiber membrane. The main operating parameter, namely the effects of pH, polymer composition and metal ions concentrations, were significantly affected by the rejection coefficient conducted at constant pressure and flowrate. Unmodified starch and PEG as binding polymers performed complexation interactions due to physical attraction of metal ions to the polymer on the molecular surface with high possibility of chemical occurrence. Rejection values were high at pH 7 for Zn (II) and Cr (III) ions corresponding to higher rejections with unmodified starch. Pb (II) ions obtained high rejections when tested with PEG whenever carried out in mixed metal ions solutions. The rejection of these metal ions by starch in this study is found to be influenced by granule structure that generally behaved in a non-ionic manner.