Green synthesis of a highly efficient biosorbent for organic, pharmaceutical, and heavy metal pollutants removal: Engineering surface chemistry of polymeric biomass of spent coffee waste

The current study reports synthesis and characterization of an ecofriendly, cheap and efficient biosorbent, sulfonated spent coffee waste (SCW-SO3H) for water remediation. SCW-SO3H was synthesized through introducing sulfonic acid polar functionalities over the polymeric biomass (cellulose and lignin) of the spent coffee waste (SCW) by a simple, facile and versatile method. ICP-OES, SEM-EDX, FT-IR, XPS, TGA, Raman and UV-vis spectroscopy were used to analyze the developed SCW-SO3H biosorbent and its adsorption capacity towards the removal of different environmental pollutants. In order to optimize and maximize adsorption capacity of the developed biosorbent, different variables such as initial concentration, biosorbent dosage, pH, time and temperature were evaluated. The chemically engineered biosorbent showed excellent pollutant removal capacity of 812 mg/g, 462 mg/g and 302 mg/g toward methylene blue, tetracycline and Cr (VI), respectively. Isotherms studies showed that while organic pollutants adsorption follow Langmuir isotherm, Cr(VI) adsorption follows Freundlich isotherm. It was also found that adsorption of all the adsorbates follow pseudo-second order rate kinetic and thermodynamic values, Delta H > 0 and Delta G < 0, showed endothermic nature as well as spontaneity of the adsorption process. The present study can provide a platform in developing new generation of eco-friendly, cost-effective and efficient biosorbent for environmental remediation.