Modification of Lignocellulosic Materials with a Mixture of m-DMDHEU/Choline Chloride to Remove CrO₄^2–, NO₃^–, and H₂AsO₄^– in Aqueous Solution

Abstract

A new denaturation agent is the mixture of 4,5-dihydroxy-1,3-bis(methoxymethyl)imidazolidin-2-one ( m -DMDHEU)/choline chloride (CC) introduced to modify three kinds of lignocellulosic materials containing different lignin contents in the following order: cotton used in medicine < sawdust from acacia auriculiformis wood < powder from the coconut shell. The modification process is carried out through two main steps: 0.2 N NaOH solution with 70% v/v ethanol and 30% v/v water was applied to remove lignin and activate the initial raw materials, and then delignified materials were modified with m -DMDHEU/CC by using a parched heat supply method after chemical impregnation. Structural characterictics and physicochemical properties of modified materials were tested and dissected by scanning electron microscopy, Fourier transform infrared spectroscopy, solid-state 13 C nuclear magnetic resonance spectroscopy (solid-state 13 C CP-MAS NMR), specific surface area, and pH at the point of zero charge (pH PZC ). The ability to adsorb and exchange anions of modified materials was referred and examined by using aqueous solutions containing CrO 4 2– , NO 3 – , and H 2 AsO 4 – anions in different conditions. The results revealed that anionite lignocellulosic materials could separate these anions with very good efficiency and better than strong anion exchange resin (GA-13) in the same conditions; outlet water could meet the permissible drinking and living water standards; and the m -DMDHEU cross-link bridge also was a good bridge to connect CC to cellulose chain beside other common urea cross-link bridges.