Adsorption/photodegradation of methylene blue using a sulfur-1,3-diisopropenylbenzene copolymer†

This study aims to utilize sulfur-1,3-diisopropenylbenzene (S-DIB) to develop a more cost-effective treatment method for dye-contaminated wastewater. The behavior and mechanisms of adsorption and photodegradation on the removal of methylene blue (MB) by S-DIB in water were studied systematically, including three isotherm model fitting tests, kinetics and thermodynamic analysis. With the optimization of the adsorption experimental conditions, the results revealed that S-DIB achieved a 96.53% removal percentage of MB at pH 11, initial dye concentration of 8 mg L⁻¹, adsorbent dose of 20 mg, temperature of 293 K and contact time of 180 min. The adsorption data fitted well with the Langmuir isotherm and pseudo-second order models, with regression coefficients (R²) of 0.9990 and 0.9993, respectively. Thermodynamic studies showed that the adsorption of MB by S-DIB was exothermic and spontaneous. Furthermore, S-DIB exhibited a unique photodegradation property in visible light regions with the removal of MB from water, offering a dual mechanism of adsorption and photodegradation, with a degradation efficiency is 94%. This work enhances the possibilities and potential for the application of sulfur-rich copolymers in wastewater treatments.