Dual immobilization of magnetite nanoparticles and biosilica within alginate matrix for the adsorption of Cd(II) from aquatic phase

Abstract

The adsorption of cadmium ions by magnetite (Fe3O4)@biosilica/alginate (MBA nano-hybrid) was the main aim of the present investigation. Herein, MBA nano-hybrid was synthesized via chemical precipitation technique. As-synthesized MBA nano-hybrid was characterized using FT-IR, FESEM and XRD analyzes. Based on the results, the maximum adsorption capacity of the adsorbent for the removal of Cd(II) was obtained at the initial pH of 7.0. At the initial Cd(II) concentration of 40 mg/L, increasing the reaction time to 180 min led to the Cd adsorption of 35.36 mg/g. Since the removal of Cd(II) after the reaction time of 60 min was insignificant, the reaction time of 60 min was considered as optimum reaction time for performing the experimental runs. According to the results, Langmuir isotherm and pseudo-second order kinetic models were the best fitted models with high correlation coefficients (R2 > 0.99). The results of thermodynamic study indicated exothermic (positive ΔH°) and spontaneous nature (negative ΔG°) of the adsorption of Cd(II) on the surface of MBA nano-hybrid. Negligible reduction in the adsorption capacity of the nano-hybrid was observed (16.57%) after fifth experimental runs, indicating high reusability potential of the as-synthesized nano-hybrid adsorbent.

Dodonaea angustifolia Extract-Assisted Green Synthesis of the Cu2O/Al2O3 Nanocomposite for Adsorption of Cd(II) from Water

“…According to the findings of other studies, the maximum Cd removal typically took place in the pH range of 4–8 (weakly acidic and neutral), which is consistent with the findings of the current study . The studies by Asgari et al saw the greatest Cd removal at pH 7 …”

“…The removal efficiency of Cd­(II) by A1 2 O 3 and Cu 2 O/Al 2 O 3 was tested at different selected pH values (2–10), with adsorbent dose = 0.3 g, contact time = 60 min, and initial concentration of Cd­(II) = 0.2 mg/L (Figure a). The effectiveness of Cd adsorption relied on the protonation as well as deprotonation of the surface functional groups of the nanocomposite . The maximum removal efficiency for Cd­(II) by A1 2 O 3 and Cu 2 O/Al 2 O 3 was observed at a pH value of 8, which is 87.77 and 96.17%, respectively (Figure a).…”

“…In addition, to explain the mechanism of Cd(II) adsorption, the Langmuir model (eq ) and the widely used empirical Freundlich model (eqs and ) were used. The Freundlich model is valid for sorption on a nonhomogeneous surface and demonstrates multilayer adsorption. , q normale = q normalm K normalL c normale 1 + K normalL c normale q normale = K normalF c normale 1 / n ln nobreak0em.25em⁡ q normale = ln nobreak0em.25em⁡ K normalF + 1 n 0.25em ln nobreak0em.25em⁡ c normale where the highest monolayer adsorption capacity is indicated by q m (mg/g), K L indicates the constant of the Langmuir equation, which is correlated to the energy of adsorption (L/g), q e is the quantity of Cd(II) adsorbed on the surface of the nanocomposite at equilibrium in mg/g, K F is the Freundlich isotherm constant in L/mg, n = adsorption capacity, and c e is the equilibrium concentration of Cd(II) in mg/L. Figure a–d and Table show the Cd(II) ion sorption isotherms on Al 2 O 3 NPs and the Cu 2 O/Al 2 O 3 nanocomposite.…”

“…This could be due to limited adsorption sites in the adsorbent material. Since a fixed quantity of the adsorbent is used, the sites become saturated at a certain concentration, making the saturated adsorbent incapable of absorbing any more Cd­(II). ,, …”

“…Since a fixed quantity of the adsorbent is used, the sites become saturated at a certain concentration, making the saturated adsorbent incapable of absorbing any more Cd-(II). 30,33,36 3.2. The removal efficiency was fast at the start of the adsorption process, achieving 97.36% and then reaching nearly a plateau later on.…”