Preparation of PHB/Chitosan/PEG Biodegradable Composite Films and Evaluation of Their Methyl Orange Adsorption Performance

Methyl orange (MO) is an azo dye widely used in the textile and pharmaceutical industries. Since MO-containing wastewater may cause environmental problems, effective adsorbent materials are needed. Chitosan (CTS) has good adsorption ability but poor water resistance and low mechanical strength. To address these limitations, Polyhydroxybutyrate (PHB) was introduced to improve the composite structural stability, while polyethylene glycol (PEG) was added to improve film flexibility and pore size. As a result, these materials were blended to prepare a biodegradable PHB/CTS/PEG (1:4:1, w/w) adsorbent with improved adsorption properties. CTS and PEG dissolved in 2% acetic acid were added dropwise into boiling glacial acetic acid containing dissolved PHB under continuous stirring. The resulting transparent mixture was cast onto a preheated (~70 °C) Teflon sheet and dried to obtain the PHB/CTS/PEG composite film for MO adsorption. The effect of contact time (1-9h), pH (4,5,7,8,9,10), temperature (25,30,35 °C) and dye concentration (100-400 mg/L) on the adsorption capacity of PHB/CTS/PEG adsorbent was investigated. The MO concentration was measured using a UV–Vis Spectrophotometer at OD463. The results showed that high adsorption occurred in acidic conditions (93.58 mg/g at pH 4). Similarly, Adsorption at 25 °C was higher than that at 30 °C and 35 °C, suggesting that the adsorption process is exothermic. The MO adsorption increased with time, and the maximum adsorption was observed at 6 h (93.87 mg/g) before attaining the equilibrium. Similarly, the adsorption capacity non-linearly increased with MO concentration. It rose sharply between 100-200 mg/L and then plateaued up to 467.99 mg/g at 300 mg/L. In conclusion, PHB/CTS/PEG adsorbent showed efficient removal of MO. In the future, we will examine the adsorption kinetics, isotherms, and thermodynamics of the data. We will also examine the film surface before and after adsorption by SEM.