The effect of temperature and pH on adsorption-desorption of fungicide hexaconazole was studied in two Malaysian soil types; namely clay loam and sandy loam. The adsorption-desorption experiment was conducted using the batch equilibration technique and the residues of hexaconazole were analysed using the GC-ECD. The results showed that the adsorption-desorption isotherms of hexaconazole can be described with Freundlich equation. The Freundlich sorption coefficient (Kd) values were positively correlated to the clay and organic matter content in the soils. Hexaconazole attained the equilibrium phase within 24 h in both soil types studied. The adsorption coefficient (Kd) values obtained for clay loam soil and sandy loam soil were 2.54 mL/g and 2.27 mL/g, respectively, indicating that hexaconazole was weakly sorbed onto the soils due to the low organic content of the soils. Regarding thermodynamic parameters, the Gibb’s free energy change (ΔG) analysis showed that hexaconazole adsorption onto soil was spontaneous and exothermic, plus it exhibited positive hysteresis. A strong correlation was observed between the adsorption of hexaconazole and pH of the soil solution. However, temperature was found to have no effect on the adsorption of hexaconazole onto the soils; for the range tested.

This study investigates the adsorption and desorption capacities of corn cob biochars produced at three different pyrolysis temperatures. Adsorption experiments were conducted using ammonium (NH4+) and nitrate (NO3-) solutions at concentrations 5, 10, 25, 50, and 100 mg L-1. Results indicated that CC300 biochar exhibited the highest NH4+ adsorption efficiency at lower concentrations, adsorbing 88.67% of NH4+ at 5 mg L-1. However, its adsorption capacity decreased with increasing NH4+ concentration. CC400 biochar demonstrated a balanced adsorption capacity for both NH4+ and NO3-, with 83.71% NH4+ adsorption and 87.17% NO3- adsorption at 5 mg L-1. CC500 biochar showed the highest NO3- adsorption capacity, reaching 90.05% at 5 mg L-1, but was less effective in NH4+ adsorption, particularly at lower concentrations. Desorption analysis revealed that CC300 and CC500 biochars retained NH4+ and NO3- effectively, with relatively low desorption rates. In contrast, CC400 biochar exhibited higher desorption rates, indicating a controlled nutrient release potential. The study highlights the significant influence of pyrolysis temperature on the adsorption and desorption characteristics of biochar and its suitability for specific nutrient management applications. These findings contribute to the optimization of biochar production and its effective utilization in sustainable agriculture and environmental protection.

The effect of temperature and pH on adsorption-desorption of fungicide hexaconazole was studied in two Malaysian soil types; namely clay loam and sandy loam. The adsorption-desorption experiment was conducted using the batch equilibration technique and the residues of hexaconazole were analysed using the GC-ECD. The results showed that the adsorption-desorption isotherms of hexaconazole can be described with Freundlich equation. The Freundlich sorption coefficient (Kd) values were positively correlated to the clay and organic matter content in the soils. Hexaconazole attained the equilibrium phase within 24 h in both soil types studied. The adsorption coefficient (Kd) values obtained for clay loam soil and sandy loam soil were 2.54 mL/g and 2.27 mL/g, respectively, indicating that hexaconazole was weakly sorbed onto the soils due to the low organic content of the soils. Regarding thermodynamic parameters, the Gibb’s free energy change (ΔG) analysis showed that hexaconazole adsorption onto soil was spontaneous and exothermic, plus it exhibited positive hysteresis. A strong correlation was observed between the adsorption of hexaconazole and pH of the soil solution. However, temperature was found to have no effect on the adsorption of hexaconazole onto the soils; for the range tested.