A B S T R A C TIn this study, potato peel (PP) was evaluated for its ability to remove Cu(II) ions from synthetic aqueous solutions under various operating conditions in a batch process. The effect of experimental parameters such as adsorbent dose (0.25-1.5), initial pH (2-5), stirring speed (0-800 rpm), temperature (25-55˚C), ionic strength (0.25-5 g/400 mL), adsorbent particle size (0.16-1.5 mm), and initial Cu(II) concentrations (25-300 mg/L) on the removal of Cu(II) was investigated. The adsorption kinetics uptake for Cu(II) by PP at various initial metal ions concentrations was analyzed using the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. It was found that the pseudo-second-order kinetic equation was the best applicable model to describe the adsorption kinetic data. The experimental data were analyzed by four adsorption isotherms, namely the Langmuir, Freundlich, Temkin, and Elovich models. Equilibrium data fitted well both to the Langmuir and Freundlich models with a maximum adsorption capacity of 84.74 mg/g at 25˚C. Thermodynamic parameters of Cu(II) adsorption on PP have also been calculated. These results demonstrate that the PP is a suitable adsorbent for the removal of Cu(II) ions from aqueous solutions.

In this study, an abundant agricultural waste, potato (Solanum tuberosum) peel, was used as a biosorbent material to test its suitability for removing a basic dye, methylene blue (basic blue 9), from aqueous solutions. The potato peel (PP) was characterized by infrared spectroscopy (FTIR), specific surface area, isoelectric potential (pH ZPC ), and scanning electron microscopy and the functional organic groups were determined by the Boehm titration method. The influence of operating conditions such as contact time, initial concentration of the dye, biosorbent dose, ionic strength, initial solution pH, temperature, and biosorbent particle size on dye removal was discussed. The results show that the increase of the initial concentration, dose of biosorbent material, and pH has a positive impact on the biosorption of dye. However, the ionic strength, the temperature, and particle size have a negative effect on the dye removal. Biosorption kinetic data obtained at different concentrations were modeled using the Lagergren's pseudo-first-order and Blanchard's pseudo-second-order kinetic models to determine the rate constants. It was found that the kinetics of the biosorption of dye closely followed the pseudosecond-order kinetic model. Equilibrium biosorption data were analyzed by four isotherms, namely the Langmuir isotherm, the Freundlich isotherm, the Elovich isotherm, and the Flory-Huggins isotherm. The equilibrium data were best represented by the Langmuir isotherm model, showing maximum monolayer biosorption capacity, q m , of 105.26 mg g −1 . It can be concluded that the PP has homogeneous surface energy. Thermodynamic parameters such as standard enthalpy change (ΔH˚), standard entropy change (ΔS˚), and standard free energy change (ΔG˚) were evaluated. The thermodynamic results suggest that the biosorption is a typical physical process, spontaneous, and exothermic in nature.

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This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch mode. The effect of experimental parameters such as initial dye concentration (10–40 mg/L), contact time (0–300 min), biosorbent dose (2.5–5.5 g/L), initial pH (2–8), temperature (298–328 K), and ionic strength on dye sorption was investigated. The results of both dyes show that the increase in initial concentration, contact time, temperature, and initial pH of solution leads to an increase in biosorbed quantity, unlike the effect of ionic strength. The biosorption kinetics for triphenylmethane dyes on ALP was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models proposed by the Weber–Morris equation. Equilibrium sorption data were analyzed by six isotherms, namely the Langmuir, Freundlich, Harkins–Jura, Flory–Huggins, Elovich, and Kiselev isotherms. The thermodynamic parameters were evaluated for both dyes. The thermodynamic results suggest that both dyes’ biosorption is a typical physical process, spontaneous and endothermic in nature.