Adsorptive removal of boron from aqueous solutions using peels of jering seeds (Archidendron pauciflorum): isotherm, kinetic and thermodynamic studies

The excessive presence of boron in the environment due to extensive industrial use can severely affect the ecosystem and human health, leading to health problems associated with skin and eye irritation, respiratory issues, and gastrointestinal disorders in humans. Therefore, this study investigated the potential of jering seed peels as an adsorbent for removing boron from aqueous solutions. The batch system was used to evaluate the efficiency of raw jering adsorbent (RJA), modified jering adsorbent by FeCl3 (MJA1), and modified jering adsorbent by NaOH (MJA2) under varying conditions, including pH, initial concentration, adsorbent dose, contact time, and temperature. Analysis using Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy was conducted to characterize the adsorbents, confirming the changes of jering adsorbents before and after the adsorption process. The optimal pH of boron removal efficiency was 6.5 for MJA1 and 7 for RJA and MJA2. The efficiency decreased with increasing initial concentration and temperature but increased with increasing adsorbent amount and contact time. The Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were applied to study adsorption isotherm, the Langmuir isotherm model for RJA (R2 = 0.99) and MJA1 (R2 = 0.92) and Freundlich isotherm model for MJA2 (R2 = 0.91) represented the measured sorption data well. Pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models were applied to study adsorption kinetics that fitted best to the pseudo-second-order kinetic model for RJA (R2 = 1.00) and MJA1 (R2 = 0.99) and fitted best to the Elovich kinetic model for MJA2 (R2 = 0.99). Thermodynamics was investigated, and the negative values of Delta H degrees and Delta S degrees showed that the boron adsorption is favourable, spontaneous, and exothermic and reduces system entropy as the adsorbate organizes at the solid-solute interface during the adsorption process. The jering adsorbents also showed good reusability during the initial and subsequent adsorption-desorption cycles, indicating potential recyclable adsorbents. Hence, utilizing jering adsorbents to eliminate boron from water resources can be feasible, cost-effective, and eco-friendly.