Cu(II) and Cd(II) capture using novel thermosensitive hydrogel microspheres: adsorption behavior study and mechanism investigation

Abstract

BACKGROUND: At present, various kinds of hydrogel adsorbents are applied to the treatment of heavy metal ions in wastewater. In this work, we focused on the adsorption of cadmium [Cd(II)] and copper [Cu(II)] onto microspheres of a novel thermosensitive hydrogel (NH 2 -SA/PNIPA, aminated sodium alginate/poly-N-isopropyl acrylamide), studied the effect of temperature on the phase transition of the hydrogel in detail, and discussed the influence on the adsorption behavior of metal ions in the hydrogel. RESULTS:The NH 2 -SA/PNIPA exhibited a higher adsorption efficiency under the conditions of interfering monovalent cationic and neutral pH. The adsorption capacities based on the Langmuir model were 57.2 mg g -1 for Cu(II) and 100.5 mg g -1 for Cd(II) at 20°C, respectively. Higher temperature facilitated the adsorption process and also led to the volume shrinkage and hydrophobicity of NH 2 -SA/PNIPA. The metal ions had different hydration and hence different adsorption capacities, of 56.7 mg g -1 for Cu(II) and 88.6 mg g -1 for Cd(II) at 40°C. The results of diffusion behavior analysis showed that the diffusion coefficients were ≈1 × 10 −11 m 2 s -1 . The adsorption performance of NH 2 -SA/PNIPA hardly decreased even after five cycles. In addition, the adsorption process was controlled mainly by the complexation reaction. CONCLUSION:The novel hydrogel microspheres overcame the deficiency of conventional adsorbents and possessed high diffusibility. This work provides a theoretical basis and empirical evidence for enhancement of adsorbents for removing heavy metals in wastewater.

The Effect of Supramolecular Humic Acids on the Diffusivity of Metal Ions in Agarose Hydrogel

“…The method used in this work belongs to the diffusion in semi-infinite medium, where the diffused particles penetrate into hydrogel and their concentration on the end of hydrogel sample is unchanged during the experiment. The incorporation of humic acids into the hydrogel resulted in the decrease in diffusivity of a magnitude comparable with values published in [ 51 , 52 ].…”

“…Their values for copper ranged between 5.5 and 6.6 × 10 −10 m 2 ·s −1 . In contrast, the values of diffusion coefficients were lower in magnitude (e.g., 4.75 × 10 −11 m 2 ·s −1 [ 51 ] and 2.12–3.12 × 10 −11 m 2 ·s −1 [ 52 ]). Our value of D g for pure agarose hydrogel is lower in comparison with the diffusion coefficients published in [ 47 , 48 , 49 , 50 ].…”

Investigating the adsorption behavior of functional biochar-based porous composite for efficiently removing Cu(ii) in aqueous solution

“…S4, ESI†). Meanwhile, EDTA-BIOC hydrogel showed higher adsorption capacity (93.9 mg g −1 ) than other adsorbents, such as (p(HEMA- co -TACYC)) hydrogel, 44 NH 2 -SA/PNIPA hydrogel, 45 PAM/GO hydrogel, 46 MPCB hydrogel 47 and KCTS/PAM hydrogel. 48…”

κ-Carrageenan/Sodium Alginate: A New Synthesis Route and Rapid Adsorbent for Hydroxychloroquine Drug

“…The pseudo-second-order and pseudo-first-order kinetic models displayed greater R 2 scores than the other models (Table 4), showing that the adsorption process is a heterogeneous diffusion process and that κC/Sa hydrogels contain several types of binding sites. There is contact between HCQ and the adsorbent, and near the border of the adsorbent particle, the adsorption resistance is concentrated [42]. It is discovered by fitting that the adsorption of κC/Sa hydrogel on HCQ is in good agreement with a more precise forecast of adsorption capacity is made when using a pseudo-second- order kinetic model and a correlation coefficient of 100%.…”