The production of activated biochar using Calophyllum inophyllum waste biomass and use as an adsorbent for removal of diuron from the water in batch and fixed bed column

Abstract

The Calophyllum inophyllum species annually produces a large volume of cylindrical fruits, which accumulate on the soil because they do not have nutritional value. This study sought to enable the use of this biomass by producing activated biochar with zinc chloride as an activating agent for further application as an adsorbent in batch and fixed bed columns. Different methodologies were used to characterize the precursor and the pyrolyzed material. Morphological changes were observed with the emergence of new spaces. The carbonaceous material had a surface area of 468 m² g⁻¹, D_p = 2.7 nm, and V_T = 3.155 × 10⁻¹ cm³ g⁻¹. Scientific and isothermal studies of the adsorption of the diuron were conducted at the natural pH of the solution and adsorbent dosage of 0.75 g L⁻¹. The kinetic curves showed a good fit to the Avrami fractional order model, with equilibrium reached after 150 min, regardless of the diuron concentration. The Liu heterogeneous surface model well represented the isothermal curves. By raising the temperature, adsorption was encouraged, and at 318 K, the Liu Q_max was reached at 250.1 mg g⁻¹. Based on the Liu equilibrium constant, the nonlinear van’t Hoff equation was employed, and the ΔG° were < 0 from 298 to 328 K; the process was exothermic nature (ΔH⁰ = −46.40 kJ mol⁻¹). Finally, the carbonaceous adsorbent showed good removal performance (63.45%) compared to a mixture containing different herbicides used to control weeds. The stoichiometric column capacity (q_eq) was 13.30 and 16.61 mg g⁻¹ for concentrations of 100 and 200 mg L⁻¹, respectively. The length of the mass transfer zone was 5.326 cm (100 mg L⁻¹) and 4.946 cm (200 mg L⁻¹). This makes employing the leftover fruits of the Calophyllum inophyllum species as biomass for creating highly porous adsorbents a very effective and promising option.