A crosslinked carboxymethyl chitosan hydrogel (CCMCH) and resin (CCMCR) are prepared via the cross-linking of glutaraldehyde. The adsorption behavior and mechanism of CCMCH and CCMCR are studied for the removal Co(II) from wastewater and their differences have been studied. The results indicate that their adsorption occurs mainly by chemical adsorption mechanism. However, the Co(II) adsorption process on CCMCH is accompanied by physical adsorption. The maximum adsorption capacities for Co(II) uptake are 72.84 and 60.03 mg g−1 for CCMCH and CCMCR, respectively, under optimized conditions. The adsorption of Co(II) on CCMCH and CCMCR are both well fitted by the Langmuir isotherm and pseudo-second-order model. Also, the data of the adsorption kinetics for Co(II) on CCMCH follows the pseudo-first-order model. Analyses from FTIR and supplemental experiments confirm that the functional groups, including amino, hydroxyl, and carboxyl groups, are involved in the adsorption process.
Xiaohong Wang,Haiqian Hou,Yujun Li,Yingying Wang,Chen Hao,Cunwang Ge
A range of super-absorbent semi-IPN hydrogels—polyvinyl alcohol/poly (acrylic acid-co-acrylic amide) (PVA-P(AA-co-AM)) were synthesized via free radical polymerization method under ultrasound-assisted condition. L 16 (4 5 ) orthogonal experiments were designed to optimize the synthesis conditions and the success was characterized by FTIR, SEM and TGA. Swelling capacities were studied in various pH solution and saline solution whose results indicated that pH in solution shows an obvious influence on it and the salt resistance is greater in salt solution of low valence relative to that of high valence. Meanwhile, its swelling behavior was evaluated in water solution, which revealed that the swelling process conformed to the Schott model and the diffusion type was non-Fickian diffusion. Moreover, the adsorption on cobalt (II) from aqueous solutions was also investigated in the paper. The optimum pH value was found close to 4 for the cobalt (II) adsorption and it was discovered that adsorption kinetics and adsorption isotherms for cobalt (II) were in accordance with the pseudo-second-order model and the Freundlich model respectively. Besides, thermodynamic parameters were calculated for the cobalt (II) adsorption and the findings revealed that the adsorption behavior is spontaneous and endothermic.
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