Facile synthesis of novel zinc sulfide/chitosan composite for efficient photocatalytic degradation of acid brown 5G and acid black 2BNG dyes

Abstract

In this work, a novel ZnS/chitosan composite was fabricated as an effective catalyst for the photodegradation of Acid Brown 5G and Acid Black 2BNG carcinogenic azo dyes in the presence of ultraviolet irradiations. The as-fabricated ZnS/chitosan composite was investigated using different spectroscopic tools such as FT-IR, XRD, UV–Vis, HR-TEM, and FE-SEM. The successful synthesis of the ZnS/chitosan composite was evidenced through the obvious damage of the crystalline structure of ZnS and the appearance of characteristic XRD peaks of chitosan at 2ɵ=8.99° and 20.30°. Also, the HR-TEM and FE-SEM images of the fabricated ZnS/chitosan composite confirmed the amorphous nature of the composite via the formation of irregular shape. Besides, the estimated energy gap of ZnS/chitosan composite is 3.00 eV. At the optimum experimental conditions (pH = 7.5, irradiation time = 120 min, temperature = 35 °C, concentration of dye = 40 mg/L, volume of dye solution = 40 mL, and dosage of photocatalyst = 40 mg), the fabricated ZnS/chitosan composite showed 97.38 and 99.32% degradation for A-5G and A-2BNG dyes, respectively. The degradation process obeyed pseudo-first-order. The ZnS/chitosan composite was easily regenerated and reutilized for three sequential cycles. The data showed that the ZnS/chitosan composite is regarded as a cost-effective, highly productive, and auspicious photocatalyst.