FTIR, Raman, and XPS analysis during phosphate, nitrate and Cr(VI) removal by amine cross-linking biosorbent

This study explores the potential use of amine cross-linked reed (ACR) for removing nitrate, phosphate and Cr(VI) from aqueous in a fixed-bed column. Characteristics (surface area, pore structure, FTIR, Raman spectra, XPS, zeta potential and solid NMR) of ACR as well as anions laden samples were intensively investigated. Results indicated that FTIR, Raman and XPS of nitrate and phosphate laden ACR were quite different from those of Cr(VI) laden samples, which corresponded well to their adsorption properties. Tertiary amine group played the main role in uptake of nitrate and phosphate by electrostatic attraction. Characteristics of Cr(VI) laden samples indicated that a reduction of Cr(VI) to Cr(III) occurred on surface of ACR (this was also proved by the zeta potential analysis). However, the main adsorption mechanism for Cr(VI) onto ACR was still based on electrostatic attraction. The maximum dynamic adsorption capacity of ACR for nitrate, phosphate and Cr(VI) was estimated to be 118.9 mg/g, 103.1mg/g and 135.3mg/g. The nitrate/phosphate adsorption capacities of spent ACR after 3 cycles of adsorption-desorption were recovered with 97.3-98.4%. In contrast, only 49.2% of Cr(VI) recovery was achieved, partially due to the destruction of the functional groups on surface of ACR during the Cr(VI) adsorption.