Abstract
A novel carboxymethyl cellulose (CMC)-supported graphene oxide aerogel (CGOA) was fabricated from a cost-effective and abundant bituminous coal by a mild hydrothermal process and freeze-drying treatment. Such an aerogel has cross-linked graphene oxide layers supported by CMC, and therefore, displays high mechanical strength while having ultra-low density (8.257 mg·cm−3). The CGOA has a 3D interconnected porous structure, beneficial graphene framework defects and abundant oxygen-containing functional groups, which offer favorable diffusion channels and effective adsorption sites for the transport and adsorption of dye molecules. The adsorption performance of rhodamine B by an optimized CGOA shows a maximum monolayer adsorption capacity of 312.50 mg·g−1, as determined by Langmuir isotherm parameters. This CGOA exhibited a better adsorption efficiency (99.99%) in alkaline solution, and satisfactory stability (90.60%) after three cycles. In addition, adsorption experiments on various dyes have revealed that CGOA have better adsorption capacities for cationic dyes than anionic dyes.
Highlights
Water pollution has become one of the most urgent global environmental issues due to the rapid development of modern industry worldwide
Afterwards, about 5 mL of H2O2 (30 wt %) was added into the mixture suspension drop by drop until the appearance turned bright yellow. This yellow mixture was separated by centrifugation (8000 rpm, 6 min), and the remaining solid was subsequently washed with 5 wt % HCl solution and deionized water several times; the final resultant solid was ultrasonicated in deionized water for 75 min to obtain a coal-based grapheme oxide suspension
From the SEM images, it can be seen that CGOA-3 has three-dimensional frameworks with randomly opened macroporous structures (Figure 2c,f), which may provide channels for the migration of dye molecules
Summary
Water pollution has become one of the most urgent global environmental issues due to the rapid development of modern industry worldwide. Many techniques and processes have been applied for the treatment of dyes from wastewater, including photocatalytic degradation [7], membrane separation [8], chemical precipitation [9], biological oxidation [10], and adsorption [11] Among these methods, adsorption is considered an effective and promising approach, because it has the advantages of low-cost, convenient operation, no secondary pollution, and recyclability [12,13]. Varaprasad K. et al conducted preparation on dye removal CMC-Acrylamide-GO hydrogels (GO, 0.05~0.14 wt %) by a free-radical polymerization method; the resulting maximum acid blue absorption capacity was 185.45 mg·g−1 [45] These methods have successfully synthesized various 3D CMC/GO composite materials, and the introduction of GO contributes significantly to the Nanomaterials 2018, 8, 670 adsorption properties of the material, surprisingly, little attention has been devoted to the effects of a high quality proportion of graphene on the adsorption properties of materials. Its dependence on other parameters such as solution pH, regeneration performance, and different dyes were investigated
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