Zeolitic imidazolate framework-67 in chitosan-grafted hydrogel as an effective catalyst for peroxymonosulfate activation to degrade antibiotics and dyes

Abstract

Zeolitic imidazolate framework-67 (ZIF-67) was synthesized in situ in the hydrogel of chitosan-grafted poly(acrylic acid) (chitosan-g-PAA) to activate peroxymonosulfate (PMS) and degrade tetracycline (TC). The catalytic performance of the composite hydrogel for TC degradation was evaluated under different conditions. The results showed rapid degradation, with enhanced degradation efficiency as the catalyst dosage, PMS dosage, and temperature increased. TC was degraded entirely within 30 min for catalyst and PMS dosages of 1 and 1 g per L, respectively. The composite hydrogel was effective across a broad pH range. A scavenging study and electron paramagnetic resonance experiments indicated that SO₄˙⁻, HO˙, O₂˙⁻ and ¹O₂ were involved in the degradation process. The antibacterial test against E. coli showed that the products of the TC degradation were nontoxic. Additionally, the composite hydrogel was evaluated in the presence of anions and in real water samples. The reusability study showed that the composite hydrogel could be recovered through filtration and effectively used for five consecutive cycles. Moreover, the composite hydrogel could degrade 82% ciprofloxacin and 86% norfloxacin, while it could completely degrade rhodamine B, reactive red 141, and methylene blue dyes within 30 min.