Continuous purification of simulated wastewater based on rice straw composites for oil/water separation and removal of heavy metal ions

An efficient continuous purification strategy based on rice straw (RS) composites for oil/water separation and removal of heavy metal ions is reported. Superhydrophobic octadecanoyl bonded and polystyrene grafted RS (C18-RS-g-PS) and aminated poly(styrene-co-acrylonitrile) grafted RS (RS-g-APSAN) were prepared by surface-initiated ATRP for the treatment of heavy metal ions contained oil/water mixtures. The efficiency of oil/water separation and subsequent adsorption behaviors of heavy metal ions including contact time, pH effect, adsorption kinetics and adsorption isotherms were evaluated systematically. The results showed that C18-RS-g-PS possessed high superhydrophobicity with water contact angle of 154 degrees and demonstrated good separation efficiency of above 98%. Regarding above separated water with contaminated heavy metal ions, RS-g-APSAN displayed high adsorption capacity towards Pb2+, Cu2+, Zn2+, and Ni2+ with adsorption capacities of 662.9, 248.8, 110.1, and 94.9 mg/g, respectively. The superior comprehensive performance of RS composites makes them potential ideal candidates for continuous purification of oily wastewater.