Synergism of CuS and tartaric acid in the reduction of Cr(VI) under an irradiation of simulated solar light

ABSTRACT

The synergism of CuS and tartaric acid (TA) in the reduction of Cr(VI) with an irradiation of simulated solar light was investigated through observing the effects of solution pH, temperature, CuS loading and TA concentration on the removal efficiency of Cr(VI). Approximately 32% and 54% of the initial Cr(VI) (100 µmol/L) were reduced within 180 min by TA and CuS with light, respectively. Under the same condition, however, almost a complete removal of the initial Cr(VI) was achieved within 130 min in the coexistence of CuS and TA. In the case, it is considered that Cr(VI) was rapidly reduced in two main pathways. One is that H₂S produced from the dissolution of CuS in weak acidic solution directly reduced Cr(VI) to Cr(III). The other is that Cu(II) released from CuS reacted with TA to form complexes with photochemical activity, producing Cu(I) through ligand-to-metal electron transfer, and then the reduction of Cr(VI) was coupled with a conversion of Cu(I) to Cu(II). Thus, a cycle catalytic system was established for the reduction of Cr(VI). Moreover, it is observed that the reaction could be divided into two stages: the initial chemical reduction of Cr(VI) by H₂S and the later photochemical reduction of Cr(VI) by Cu(II)–TA complexes.

KEYWORDS:

• Cr(VI)
• CuS
• tartaric acid
• reduction
• simulated solar light

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [Grant No. 21607076] and the Fundamental Research Funds for the Central Universities of China [Grant Nos. KYZ201542 and KJQN201722].