Adsorption of Black MNN reactive dye from tannery wastewater using activated carbon of Rumex Abysinicus

Background A high concentration of Black MNN reactive dye in untreated tannery wastewater can cause adverse effects on public health and environmental sustainability. Therefore, this study aimed to investigate the adsorptive performance of Rumex Abyssinicus-based activated carbon (RAAC) to remove Black MNN reactive dye from tannery wastewater. Method The stem of Rumex Abyssinicus was impregnated with 50 % diluted phosphoric acid at the ratio of 1:3 (w/w biomass to acid) and then it was carbonized in the muffle furnace at 600 degrees C. The Box-Behnken experimental design of 34 was used to optimize the removal efficiencies under the response surface methodology. Significant findings Characteristics of the adsorbent were described by SEM for surface morphology with high cracks, FTIR spectrometry for multi-functional groups (O-H at 3443.08 cm-1, aromatic C = C 1633.78 cm-1, vibrational and stretching motion of -OH 1205.65 cm- 1and vibrational motion of C-O-C 1045.46 cm-1), BET with specific surface area of 3619.7 m2/g, and X-RD with amorphous structure. The maximum dye adsorption of 99.9 % was observed at experimental conditions of 150 mg/L, 0.25 mg/100 mL, pH 2, and 90 min. The experimental data were evaluated in terms of Langmuir, Freundlich, Temkin, and Spis isotherms which showed the Langmuir model was found to be the best fit with the experimental data at R2 0.99. This shows that the adsorbent surface is homogeneous and monolayer. Furthermore, the kinetic study confirms that the Pseudo second-order model best describes the experimental data at R2 0.99. Finally, statistical analysis showed that the experimental values are almost the same as the predicted data which were indicated by the Adjusted R2 0.99 and predicted R2 0.97. In conclusion, Rumex Abyssinicus is a good precursor material for adsorbent development to remediate industrial and municipal wastewater.