Recycling Polyethylene Terephthalate Waste to Magnetic Carbon/Iron Nanoadsorbent for Application in Adsorption of Diclofenac Using Statistical Experimental Design

A novel magnetic nanoadsorbent comprising carbon/iron composite was prepared from polyethylene terephthalate waste. The magnetic nanoadsorbent was characterized and applied in the adsorption of diclofenac from water. Batch adsorption experiments were conducted according to a three-factor three-level Box–Behnken design including temperature (°C), pH and adsorbent dose (g L-1) as the process parameters. A polynomial regression model was used to predict and optimize the parameters for maximum adsorption capacity (mg g-1) of the nanoadsorbent using response surface modeling. The magnetic nanoadsorbent exhibited a surface area of 288.88 m2 g-1 and a saturation magnetization of 35.4 emu g-1. Transmission electron microscopy of the nanoadsorbent depicted particle size range within 10–40 nm. The maximum adsorption capacity of the nanoadsorbent for diclofenac was 15.31 mg g-1 under optimized conditions of 42.65 oC, 5.74 pH and 1.04 g L-1 dose. High regression coefficient values (R2 = 0.987) in the design experiments suggested considerable goodness of fit for the response surface model. Statistical analysis showed adsorption of diclofenac by the nanoadsorbent was significantly influenced by solution pH. FTIR analysis of the diclofenac loaded nanoadsorbent confirmed the adsorption of diclofenac by the emergence of new diagnostic peaks. The diclofenac loaded nanoadsorbent could be desorbed up to 69.88% by NaOH stripping, suggesting its reuse potential.