One-pot high-speed shear preparation of modified straw: An efficient, convenient, nontoxic, and green method with high adsorption capacity for nitrate removal from aqueous solution

Abstract

The multistep modification of straw-based adsorbent materials has significant advantages in terms of adsorption capacity over the one-step method; however, it poses significant problems such as a complicated, time-consuming preparation process, low grafting efficiency, and widespread use of highly toxic reagents. This study presents the first application of the one-pot high-speed shear method (HSSM) for the efficient grafting of 2,3-epoxypropyltrimethylammonium chloride on wheat straw. Experimental results show that the grafting rate, BET surface area and preparation speed of HSSM increased by 4.96, 12.57 and 3.7–14.5 times, respectively, compared with those of the traditional one-step magnetic stirring heating method. The nitrate adsorption capacity was 65.45 mg g−1, which is similar to or better than that of the multistep quaternary ammonium–modified material. In addition, the proposed preparation process did not require additional heating and did not use any toxic reagents. Characterization through EDS, FTIR, Zeta, and XPS confirmed the adsorption mechanism to be ion exchange and electrostatic gravity, with the former contributing 73–79%. The proposed one-pot HSSM to prepare quaternary ammonium–modified straw is fast and simple, has high adsorption performance, and does not use highly toxic reagents. The adsorption capacity of the adsorbent remained 55.04–52.98 mg·g−1 in the range of pH 3–11. After nine adsorption and desorption cycles, the adsorption efficiency remained > 80% in the adsorbent regeneration test. This work is in accordance with the development of agricultural waste resources and green chemical development ideas.