Sustainable Removal of Pesticides from Water Using Biochars Derived from Conocarpus and Lemon Tree Waste

Pesticide residues in aquatic systems pose persistent risks to ecosystems and public health, underscoring the need for low-cost and sustainable remediation strategies. In this study, biochars prepared from Conocarpus branch waste (CBB) and lemon tree branch waste (LBB) via slow pyrolysis at 450 °C were evaluated as adsorbents for two widely applied agrochemicals: imidacloprid (IMI) and myclobutanil (MYC). Comprehensive physicochemical characterization (SEM, TEM, BET, and elemental analysis) revealed mesoporous structures with distinct surface features. Batch adsorption experiments demonstrated strong dependence on solution pH, adsorbent dosage, contact time, and initial pesticide concentration. Under near-neutral conditions (pH 7.0, 5 g L^-1, 25 °C, 24 h), maximum capacities reached 8.69 mg g^-1 (IMI) and 12.31 mg g^-1 (MYC) for CBB. Adsorption kinetics followed a pseudo-second-order model (R ² > 0.98), while equilibrium data fit both Langmuir and the Freundlich isotherms (R ² ≥ 0.99). Thermodynamic analyses (ΔG° = -1.3 to -4.5 kJ mol^-1; ΔH° = -16.4 to -29.8 kJ mol^-1) indicated spontaneous, exothermic processes dominated by physisorption. The reusability of both biochars across multiple cycles further confirmed their practical applicability. These results highlight pruning-waste biochars as effective and sustainable alternatives to conventional adsorbents for mitigating pesticide pollution in water.