Efficient adsorption/photodegradation of organic pollutants from aqueous systems using Cu2O nanocrystals as a novel integrated photocatalytic adsorbent

Abstract

In this work, novel uniform Cu₂O nanocrystals (NCs) with a size of 4 nm were synthesized by a remarkably simple and facile route via a synproportionation reaction of Cu²⁺ with metal copper powder at room temperature. The obtained Cu₂O NCs as an integrated photocatalytic adsorbent (IPCA) exhibited high adsorption affinity combined with superior photocatalytic activity for the removal of various organic pollutants (humic acid (HA), Congo red (CR), methyl orange (MO) and tetracycline (TC)) in our experiments. The results show that the Langmuir isotherms were applicable to describe the adsorption processes and the adsorption kinetics followed the pseudo-second-order mode. The adsorption mechanism that is responsible for superior adsorption capacity occurs mainly via surface complexation as well as coagulation on the surface of Cu₂O NCs. A remarkable maximum adsorption capacity toward HA (405.5 mg g⁻¹) was achieved on Cu₂O NCs, which is higher than any currently reported adsorbents. On the basis of the batch adsorption experiments, the as-prepared Cu₂O NCs as IPCA were further applied to photodegradation experiments. More than 99.5% HA molecules could be degraded within 2 h, and the photocatalytic efficiency of Cu₂O NCs did not decrease obviously after five cycles, indicating that our Cu₂O NCs are stable IPCAs. Moreover, the Cu₂O NCs also exhibit excellent degradation efficiency for other organic pollutants (99% for CR, 90% for MO, and 75% TC, respectively). In addition, more than 94% of natural organic matter (NOM) was eliminated by Cu₂O NCs from real wastewater, which is served as drinking water in Togtoh County, Inner Mongolia, China. Therefore, obtained Cu₂O NCs can be used as a novel IPCA material for the efficient purification of NOM of contaminated ground water.