Chemical modification of sodium alginate with thiosemicarbazide for the removal of Pb(II) and Cd(II) from aqueous solutions

Abstract

A new material (Alg_Ox-TSC), based on alginate (Alg) chemically modified with thiosemicarbazide (TSC), has been synthesized and tested as an effective biomaterial to remove Pb(II) and Cd(II) ions in aqueous solutions. The synthesis was carried out by controlling the following steps, i/partial oxidation process of alginate in NaIO₄ to obtain AlgOx, ii/reacting of AlgOx, at 40-45 °C, with TSC in NaBH₄. Alg_Ox-TSC has been characterized by Field Emission Scanning Electron Microscopy (FESEM/EDS), Fourier Transform Infrared Spectroscopy (ATR-IR), solid state ¹³C NMR spectroscopy and Point of Zero Charge (pH_PZC) measuremenmts. In order to enhance the sorption process, the effect of contact time, sorbent dosage, initial concentration and reusability of the novel sorbent were investigated becoming the Alg_Ox-TSC a promising material capable of removing high concentrations of heavy metal ions such as Pb(II) (up to 950 mg/g at pH 3) and Cd(II) (up to 300 mg/g at pH 7) in aqueous solutions.

Keywords: Alginate; Cd(II); Chemical modification; Pb(II); Thiosemicarbazide.