Prospective Sorption Evaluation of Hydrothermally Carbonized Lepironia Articulata (Grey sedge) for the Removal of Ni (II) from Aqueous Solution

Abstract

As an alternate to pyrolysis, hydrothermal carbonization has been proposed as a promising technique for conversion of different wastes into biofuels, adsorbents and specific chemicals. Different types of biomass wastes were used for converting to adsorbent by researchers and their potential to adsorb heavy metals was reported to be excellent. This paper presents the efficiency of hydrochar produced from an alternate biomass lepironia Articulata (LA) through series of activation and carbonization methods for the removal of Ni (II) from aqueous solution, as well as proposed methods of improving hydrochar surface reactivity. Hydrochar produced at 200 °C with a maximum yield of 60% and with an improved surface functional group was selected as an adsorbent. The kinetic study, pH effect, an effect of Ni (II) initial concentration, and adsorbent dose were examined in batch experiments. Fourier Transform Infrared Spectroscopy (FT-IR) was employed to characterize the resulting lepironia articulata hydrochar (LAHC). The results of this characterization showed that after the hydrothermal carbonization, the functional groups from fresh biomass were preserved. Based on FT-IR results it can be concluded that the metal binding in biomass of LA takes place by the substitution of Ni (II) ions by an amine, nitro, and carboxylic functional groups. Furthermore, adsorption data for Ni (II) uptake by hydrochar were analyzed according to Langmuir and Freundlich adsorption models. It was noticed from results that maximum uptake percentage of Ni (II) was 72.77% at the initial concentration of 100 mg L-1 and pH 6. The adsorption equilibrium was established in 180 minutes. The maximum adsorption capacity (qm) calculated is 12.2 mg g-1. Through above evident results it has been proved that the low-cost hydrochar prepared from LA has potential to adsorb Ni (II) from aqueous solution.