Microwave-Assisted Modification of Corncob with Trimethylammonium Chloride for Efficient Removal of Cr(Ⅵ): Preparation, Characterization, and Mechanism

摘要

A novel aminated adsorption material, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA)-modified corncob (CTAMC), was successfully synthesized by microwave irradiation assisting method for Cr(VI) removal from aqueous solutions. The preparation conditions and physicochemical properties of CTAMC and the Cr(VI) removal mechanism were investigated. Results showed that the optimal preparation conditions were 1.0 g of corncob treated with 55 g/L sodium hydroxide for 80 min, 30% CTA, and 480 W of microwave power treatment for 5.0 min. These conditions resulted in the yield of CTAMC of approximately 60%, and the sodium hydroxide concentration exhibited great influence on the yield. The Cr(VI) adsorption capacity of CTAMC reached 38 mg/g, which was 9 times higher than that of the raw corncob. Results from the field-emission scanning electron microscopy and energy dispersive spectroscopy characterization showed that the surface structure of CTAMC was rougher than that of raw corncob; the fiber structure was more apparent, and the content of N and Cl elements were significantly increased, which indicated that CTA was successfully grafted on the surface of corncob. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis demonstrated that the quaternary amino group (-NH-), hydroxyl (C-OH), and chloride ion (Cl-) were primarily involved in the Cr(VI) removal process, revealing that Cr(VI) was removed by both adsorption and reduction. This study provides an alternative for the removal of Cr(VI) and further broadens the utilization of agricultural waste.