Two-three parameters isotherm modeling, kinetics with statistical validity, desorption and thermodynamic studies of adsorption of Cu(II) ions onto zerovalent iron nanoparticles.

Adsorption of problematic copper ions as one of the endocrine disruptive substances from aqueous solution onto nanoscale zerovalent iron (nZVI) was studied. The high pore size 186.9268 Å, pore diameter 240.753 Å, and BET surface area 20.8643 m2 g-1 and pH(pzc) enlisted nZVI as an efficient nano-adsorbent for treatment of heavy metals from synthetic wastewater. SEM and EDX revealed the morphology and elemental distribution before and after adsorption. 98.31% removal efficiency was achieved at optimum adsorption operational parameters. Of all the thirteen isotherm models, equilibrium data were well fitted to Langmuir. Kinetics and mechanism data across the concentrations from 10 to 200 mg L-1 were analyzed by ten models. PSO best described kinetics data as confirmed by various statistical error validity models. The intraparticle diffusion model described that the intraparticle diffusion was not the only rate-limiting step. The adsorption mechanism was diffusion governed established by Bangham and Boyd models. Feasible, spontaneous, endothermic, and degree of randomness were reveal by the thermodynamic studies. Better desorption index and efficiency were obtained using HCl suggesting multiple mechanism processes. The performance of ZVI suggested it has a great potential for effective removal of endocrine disruptive cationic contaminant from wastewater.

Sustainable and low-cost Ocimum gratissimum for biosorption of indigo carmine dye: kinetics, isotherm, and thermodynamic studies.

In the quest for a sustainable environment and clean water resources, the efficacy of Ocimum gratissimum leave (OGL) for indigo carmine (IC) dye biosorption was studied in a batch technique. The physicochemical properties of OGL supported its suitability for biosorption studies. Of 92.6% removal efficiency was achieved at optimum conditions of pH 2, contact time 120 min, initial IC concentration 500 ppm, temperature 298 K, and 100 mg OGL dose. Kinetic data were best fitted to pseudo second-order (PSO) and the mechanism was pore diffusion governed as validated by sum of square error (SSE) and non-linear chi-square (χ 2). Freundlich isotherm model gave the best description at 298 K as supported by Halsey, Redlich-Peterson, and Fowler-Guggenheim confirming the heterogeneous nature of OGL and multilayer biosorption process. Langmuir Q max (77.52 mg g-1) surpassed those previously reported. SEM and EDX confirmed the reality of the biosorption process. Thermodynamic parameters (ΔH°, ΔS°, ΔG°, and Ea) affirm a feasible, spontaneous, exothermic, and randomness of the process. Results revealed that OGL is a potential and efficient environmentally benign, low cost, and sustainable biosorbents. It is therefore recommended as a bi-functional biosorbent for wastewater treatment.