Modification of Lignocellulosic Materials with a Mixture of m-DMDHEU/Choline Chloride to Remove CrO42–, NO3–, and H2AsO4– in Aqueous Solution

摘要

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.