Production of activated biochar from Luffa cylindrica and its application for adsorption of 4-Nitrophenol

Abstract

Activated biochar was prepared from dried Luffa cylindrica fruits as a convenient source of carbon-rich biomass. In this regard, a commonly practiced single-step H3PO4 pretreatment and combined H3PO4 and H2SO4 treatments before and after the pyrolysis were utilized for the production of loofah-derived biochar (LB) and sulfuric acid-treated LB (SLB). These biochars were compared in terms of physicochemical characteristics and the potential for removal of 4-Nitrophenol (4NP). It was indicated that the adsorption of 4NP was more efficient on SLB compared to LB with a Langmuir maximum monolayer adsorption of 436.6 mg/g vs 265.4 mg/g at 30 °C. Thermodynamic studies demonstrated that the adsorption process was endothermic and associated with entropy increase for both biochars. BET analysis showed that the surface area of LB and SLB were 28 and 46 times as high as that of non-activated carbonized loofah, respectively. Based on the analysis of the surface functional groups by FTIR spectroscopy and N2 adsorption-desorption experiments, pore filling and hydrogen bonding were suggested as major factors contributing to the high performance of the prepared adsorbents. Other notable mechanisms for 4NP removal were π-interactions and degradation. The possibility of reusing the adsorbents and recycling the waste sulfuric acid was also investigated, demonstrating the commercial attractiveness and environmental friendliness of the produced biochars.