NaOH Modification of Persimmon Powder-formaldehyde Resin to Enhance Cu2+ and Pb2+ Removal from Aqueous Solution

Abstract

An adsorption resin (persimmon powder-formaldehyde resin, PPFR) was developed by immobilizing persimmon powder (extracted from persimmon residual) with formaldehyde in our previous work1, and it exhibited outstanding selective adsorption capacity towards Au3+ from aqueous solutions and harsh industrial acidic conditions1,2. However, its adsorption behaviour of heavy metal ions was not so good compared with the adsorption of Au3+, and it need modification to enhance its adsorption behaviour of heavy metal ions. In this study, a novel adsorbent, named “NPPFR”, was prepared by treating PPFR with NaOH, and its adsorption behaviours of Cu2+ and Pb2+ from aqueous solutions was investigated. The effects of solution pH, adsorption time, metal ion concentration and coexisting metal ions on adsorption were studied in batch experiments. The adsorption capacity of Cu2+ and Pb2+ on NPPFR was much higher than that of PPFR, which increased by 323% and 186% at 303K, respectively. The adsorption of Cu2+ and Pb2+ onto PPFR and NPPFR was highly affected by pH, and the optimal pH range was 5.0-6.0. Both adsorption kinetics of Cu2+ and Pb2+ proceeded rapidly and could be well described by pesudo-second-order equation (R2>0.99), and the adsorption capacities calculated by the model were close to those determined by experiments. The adsorption isotherms of Cu2+ and Pb2+ on PPFR and NPPFR could be well described by Langmuir equation (R2>0.99), and the maximum Langmuir adsorption capacities for Cu2+ and Pb2+ removal by NPPFR reached up to 116.28 and 384.62mg/g (303K), respectively. Coexisting metal ions (Fe3+, Pb2+, Cu2+, Cd2+, Zn2+, Mn2+, Mg2+ and Ca2+) had no obvious influence on the adsorption of Cu2+ and Pb2+ on PPFR and NPPFR. Moreover, most of metal ions coexisting in solutions could simultaneity removed by NPPFR when the adsorbent dose was 1.0g/L, while the adsorption of Mg2+ and Ca2+ on PPFR were not satisfactory at the same adsorbent dose. The results indicate that NPPFR could be employed as an effective low-cost adsorbent for adsorption of heavy metal ions from wastewater.