Green synthesis of low-cost and eco-friendly adsorbent for dye and pharmaceutical adsorption: kinetic, isotherm, thermodynamic and regeneration studies

The green synthesis of low-cost, effective and environmentally friendly adsorbent via hydrothermal carbonization with less energy and time consumption to remove rhodamine B (RhB) and ibuprofen (IBP) from aqueous solutions was investigated. The samples were characterized using scanning electron microscopy, BET-surface area analysis, x-ray diffraction, Fourier transform infrared spectroscopy and thermal gravimetric analysis. In this study, several factors which can affect adsorption behaviors, such as the initial concentration, contact time, adsorbent weight, solution pH and temperature, were also evaluated. The adsorbent surface morphology result showed the construction of carbon spherical shape on the wrinkled and scaly adsorbent surface with the average diameter of particles around 2-5 µm. The data were well fitted to Langmuir isotherm and pseudo-second-order kinetic models with the maximum adsorption capacities for RhB and IBP being 70.92 and 63.69 mg/g, respectively. The thermodynamic parameters indicated that the adsorption of RhB and IBP were spontaneous and endothermic. From the regeneration study, the used adsorbent was still maintained at 81.87 and 76 % of the original condition after six successive regeneration processes. In general, this work presents a simple green synthesis method to enhance the performance and efficiency of adsorbent for RhB and IBP removal from aqueous solution. The overall results could be considered in wastewater treatment as a strategy for environmental sustainability.