Research Article pubs.acs.org/journal/ascecg
One-Step Synthesis of Cationic Hydrogel for Efficient Dye Adsorption and Its Second Use for Emulsified Oil Separation Daikun Li, Qing Li,* Ningning Bai, Hongzhou Dong, and Daoyong Mao School of Chemistry and Chemical Engineering, Southwest University, Tiansheng Road No. 2, Chongqing 400715, People’s Republic of China S Supporting Information *
ABSTRACT: The removal of toxic dyes and insoluble oil from wastewater is a hot topic in both academic and industrial fields. Herein, we report a cationic absorbent poly(epichlorohydrin)− ethylenediamine hydrogel (PEE-Gel) via a simple one-step copolymerization and it can be successfully used for the removal of toxic dyes and insoluble oil from wastewater. The adsorption toward anionic dyes shows high efficiency and high selectivity at a wide pH range (from 2 to 12). The adsorption capacity at low equilibrium concentration (10 mg L−1) is as high as 1411.4 mg g−1 which is very close to the maximum adsorption capacity (1540.19 mg g−1). The adsorption of dye molecules onto PEEGel is very steady and can be difficult to be regenerated. The PEE-Gel with full dye adsorption (PEE-Gel-Dye) shows superoleophobicity under water, and PEE-Gel-Dye can be reused to separate toluene-in-water emulsion with high efficiency and durability. These results suggest that PEE-Gel is a promising and competitive candidate for water purification. KEYWORDS: Cationic hydrogel, Selectively adsorption, Dyes, Underwater superoleophobicity, Emulsion oil
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INTRODUCTION Water contamination with soluble dyes and insoluble oil is one of the major global environmental issues caused by industrial development.1−5 When those pollutants are discharged as untreated sewage into the environment, they affect aquatic life, as well as the food chain, and also present a serious challenge to humans.6−9 Because of the differences of physical and chemical properties of soluble dyes and insoluble oil, one approach can usually effectively remove one of the two types of pollutants.2,10 Therefore, it is of great practical significance to develop a versatile material that can remove both soluble dyes and insoluble oil from water. Nowadays, commercially dyes are widely used in dyestuffs, textile, paper, plastics, cosmetics, tannery, and paints,11,12 and over 50 000 tons of dyes are discharged into the environment annually.13,14 Because of the facts that dyes are recalcitrant, resistant to aerobic digestion, stable to oxidizing agents, and insoluble in low concentration, treatment of dyeing wastewater is a big challenge.15 Many treatment methods, including biodegradation, chemical oxidation, membrane separation, coagulation−flocculation, photocatalysis, and adsorption have been proposed to remove dyes from wastewater.16,17 Among these approaches, adsorption is considered as the most attractive technology, because of its high efficiency, economic feasibility, and simplicity of operation, as well as the wide suitability for diverse dyes.18−20 An ideal adsorbent is expected to show high adsorption capacity, fast adsorption rate, high © 2017 American Chemical Society
selectivity and low cost, simultaneously. Until now, various types of materials have been reported as high-performance adsorbents, such as porous carbon materials,21 metal−organic frameworks (MOFs),22 graphene oxides,23 polymers,24 natural minerals,25 and so on. However, most of those materials show high adsorption capacity in high concentrated dye wastewater, but poor efficiency in low concentrated dye wastewater. For example, Zhao et al. reported a β-cyclodextrin-based adsorbent, the maximum adsorption capacity of this adsorbent is as high as 826.45 mg g−1. However, the equilibrium adsorption capacity is
