Enhanced uptake of gold ions from wastewater due to covalent functionalization of organotriphosphonic acid on japonica shells

In the present work, the facile covalent functionalization of organotriphosphonic acid on japonica shells (OTPA-JS) has been developed and they were used for enhanced uptake of gold ions from wastewater. The theoretical calculations of the cellulose with organotriphosphonic acid group have been carried out at the B3LYP/6-31+G(d) level to design the bioabsorbent material OTPA-JS. The studies on the adsorption properties of japonica shells JS and OTPA-JS for Au(III), Hg(II), Cu(II), Pb(II), Ni(II), Co(II), Zn(II), Cr(III) and Cd(II) have revealed that OTPA-JS displayed excellent enhanced adsorption for gold ions compared to JS. Furthermore, the adsorption selectivity results showed that OTPA-JS had strong affinity for gold ions in the aqueous solutions and even exhibited 100% selectivity for Au(III) ions in the presence of Co(II), Zn(II), Cr(III) and Cd(II). The relevant adsorption behaviors of OTPA-JS and JS for gold ions, such as the effect of pH value, the adsorption kinetics, and thermodynamics as well, have also been investigated. The results indicated the maximum adsorption capacities of OTPA-JS at 35°C could reach 523.56 mg/g, the activation energy value for Au(III) onto OTPA-JS was –38.82 kJ/mol, and the adsorption thermodynamic parameters ∆G, ∆H and ∆S were –103.03 kJ·mol–1, 96.87 kJ·mol–1, and 334.82 J· K–1·mol–1, respectively. Moreover, the adsorption mechanism for gold ions adsorption was also investigated, which were based on the results of FTIR, XPS, SEM, and XPS of the sample after gold ions adsorption (OTPA-JS-Au). Moreover, this modified adsorbent was utilized to uptake gold ions in the gold-plating wastewater samples. Therefore, the prepared adsorbent OTPA-JS is expected to be a new biomass material for the uptake and recovery of gold from contaminated water.