Aquatic plant-derived biochars produced in different pyrolytic conditions: Spectroscopic studies and adsorption behavior of diclofenac sodium in water media

Abstract

The ubiquitous prevalence of pharmaceuticals and personal care products (PPCPs) in water has aroused enormous public concerns. The development of promising materials for eliminating such contaminants in the water environment has attracted extensive attention in the scientific community. In this study, three (350 °C, 450 °C, and 600 °C, respectively) pyrolytic conditions were developed to prepare biochars (BCs), which were mainly prepared from the wastes of the overgrown plants (i.e., vallisneria natans, potamogeton malaianus, phragmites australis, potampgeton crispus, and river sediment additional). BCs were thoroughly characterised by various important properties (i.e., porosity and superficial functional group) and applied to remove diclofenac sodium (DS) drug from water media. Results indicated that the BCs adsorption capacity were remarkably improved when pyrolytic temperature was 450 °C and the adsorption equilibrium could be reached after 4 h (with BCs of 0.12 g/L and DS concentration of 12 mg/L). Batch adsorption experiments demonstrated a fit of Pseudo-second order (R2 = 0.992-0.996) and the Langmuir adsorption isotherm (R2 = 0.981-0.989) was suitable. The thermodynamic parameters derived from the fitting procedure point out the adsorption processes were all spontaneous and endothermic. The overall adsorption mechanism was regarded as pore filling, π-π interaction, van der Waals force, and π-electron attraction. This study stress out the main DS adsorption behavior using the above-mentioned materials was chemisorption predominated, but the adsorption capacity differs with different material properties. The prepared BCs can serve as potential carbonaceous porous adsorbents for removing DS from water media.