Biosynthesis of Leucaena Leucocephala leaf mediated ZnO, CuO, MnO2, and MgO based nano-adsorbents for Reactive Golden Yellow-145 (RY-145) and Direct Red-31 (DR-31) dye removal from textile wastewater to reuse in agricultural purpose

Environmental pollution by textile dye-based wastewater raises a vital call for consideration to industrialists and scientists due to its influence on the ecosystem. In this study, zinc oxide (ZnO), copper oxide (CuO), Manganese dioxide (MnO2), and Magnesium Oxide (MgO) nanoparticles were successfully synthesized from Leucaena leucocephala leaves for the removal of Reactive Golden Yellow-145 (RY-145) and Direct Red-31 (DR-31) dyes. The nanoparticles were characterized by scanning electron microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Optimization of various operating parameters like initial dye concentration, pH, temperature, contact time, and dose of nanoparticles was investigated. The results showed that Leucaena leucocephala leaf-mediated ZnO, CuO, MnO2, and MgO nanoparticles presented the highest adsorption capacities for RY-145 of 47.50 (mg/g), 65.53(mg/g), 53.62 (mg/g), and 58.72 (mg/g) respectively, with optimized parameter values of pH solution, contact time, adsorbent dose, initial dye concentration, and temperature were 3, 75 min, 0.05 g/50 mL, 100 mg/L and 25 degrees C on 124 rpm, correspondingly. DR-31 presented the highest adsorption capacities of 57.08 (mg/g), 83.47(mg/g), 67.36 (mg/g), and 72.53 (mg/g) respectively at optimized parameter values of pH solution, contact time, adsorbent dose, initial dye concentration and temperature were 2 and 3, 60min, 0.05 g/ 50 mL, 100 mg/L and 25 degrees C on 124 rpm. The surfactants and electrolytes effects were also scrutinized on dyes' adsorption. The surfactants and electrolytes' existence in the aqueous media reduced the adsorption of dye because of the competition for limited binding sites. The RY-145 and DR-31 adsorbents adsorption efficiencies were found in following order; MgO (65.52% and 83.47%) > MnO2 (58.72% and 72.53%) > CuO (53.62% and 67.36%) > ZnO (47.50% and 57.08%). The adsorption-based dye data were scrutinized using various isotherms, kinetics, and thermodynamics models. The studies presented that the adsorption processes were well fitted to pseudo-second-order kinetics since correlation coefficient (R2) values ranged from 0.994 to 0.999 and Intraparticle diffusion models correlation coefficient values ranged from 0.88 to 0.97, their values were relatively near the experimental values signify the adsorption kinetics in both dyes. Both dyes adsorption on green nanoadsorbents followed a Langmuir isotherm due to decent correlation coefficient values of 0.999 with value of 59.17 (mg/g), 66.22 (mg/g), 72.99 (mg/g), and 81.30 (mg/g) respectively for DR-31 and 47.62 (mg/g), 53.763 (mg/g), 58.48 (mg/g), and 64.93 (mg/g) for RY-145 with monolayer coverage. RY-145 also followed Temkin and Doubinin Radushkevich's isotherm. The thermodynamics investigations revealed spontaneous dyes adsorption onto MgO and MnO2, ZnO is non-spontaneous in both dyes while CuO is spontaneous in DR-31 and nonspontaneous in RY-145. The maximum desorption of 78-86% was attained using the 0.2 N and 0.4 N NaOH for adsorbed RY-145 and DR-31 dye respectively. The desorption data was favorable as the Leucaena leucocephala leaf-mediated ZnO, CuO, MnO2, and MgO nanoparticles adsorbents were utilized several cycles and have stability This experimental study also determines the potential efficacy of green nano-adsorbents for the removal of dye from the real textile effluent. In addition, a phytotoxicity investigation of used green nano-adsorbents is carried out on the pea seeds, to demonstrate their sustainability from a real environmental point of view. Thus, Because of their promising efficiency, green ZnO, CuO, MnO2, and MgO nanoparticles have the potential to apply for dye adsorption from textile wastewater.