Chemical Oxygen Demand (COD) Attenuation of Methyl Red in Water using Biocarbons obtained from Nipa Palm Leaves

Attenuation of methyl red dyestuff in water was assessed by COD reduction after contacting the solution with biocarbons produced by one-pot pyrolysis of sopping Nipa palm leaf biomass in H₂O (physically-modified biocarbon: PMB), H₃PO₄ (acid-modified biocarbon: AMB) and KOH (base-modified biocarbon: BMB). Physicochemical characterization of the biocarbons were investigated and the result for BMB were carbon yield (46.6 ± 0.21 %), porosity (79%), iodine number (814 mg/g), surface area (681 m²/g) and pH (6.41 ± 0.11 to 7.81 ± 0.12). Optimal COD reduction for methyl red in water by PMB, AMB, BMB compared with CAC were 82.7%, 76.7 %, 83.5 %, and 93.3 % respectively. Langmuir isotherm model was used to predict the maximum COD reduction capacity of the biocarbons and CAC (PMB: 2.15 mg/g, AMB: 8.73 mg/g, BMB: 11.83 mg/g and CAC: 62.60 mg/g). Thermodynamic assessment of the data based on Gibb’s free energy (ΔG°) revealed that ΔGo values were negative (- 1.31 to - 5.89 kJ/mol) and relatively low (<< -20 kJ/mol), which indicated spontaneous nature requiring minimal energy. One-way analysis of variance (ANOVA) performed to validate the COD degradation capacity for methyl red in water amongst the biocarbons revealed no significant difference (p > 0.05). Conclusively, Nipa palm could be a favorable source to derive eco-friendly and locally accessible biocarbon for mitigation of organic contaminants in water.

Keywords
Chemical oxygen demand; biocarbon; methyl red; biodegradation; bioremediation; Nipa palm