A novel polymer coated magnetic activated biochar-zeolite composite for adsorption of polystyrene microplastics: Synthesis, characterization, adsorption and regeneration performance

A magnetic activated biochar-zeolite composite (MACZ) was produced and coated with polyethyleneglycol (PEG) and polyethylenimine (PEI) to produce (PMACZ) and enhance its electrostatic properties for the adsorption of 2 µm and 15 µm microplastics. Produced adsorbents were characterized with scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), Brunauer-Emmett-Teller (BET), zeta sizer, vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Equilibrium and kinetic laboratory tests were conducted to evaluate the adsorption behaviour. A response surface analysis (RSM) was conducted on a central composite design to evaluate the effects of pH and temperature on adsorption. Zeta potential results showed PEG/PEI can induce positive charges on adsorbents. Adsorption kinetic followed a pseudo-second-order model with R2 of 99 %. The results of isotherm studies indicated a correlation with the Temkin model with a maximum R2 of 98 %. The results showed a maximum adsorption capacity of 736 mg/g and 769 mg/g for PMACZ on 2 µm and 15 µm microplastic, respectively. Optimization results indicated a pH of 4 and a temperature of 28 and 24 for maximum adsorption of 2 µm and 15 µm microplastics. ANOVA analysis showed pH has a higher impact on adsorption. The produced material can be regenerated for a minimum of 4 cycles. The effect of ion matrixes, sea salt, tap water and waste water effluent on adsorption of MACZ and PMACZ has been investigated.