Preparation and adsorption property of phytic acid modified wood flour

  Objective  Exploring the performance of wood flour and modified wood flour from processing residues in the wood industry as an adsorbent for dye pollutants in wastewater provides a strategy for the high-value utilization of wood flour.

  Method  Wood flour-based adsorbent (PA-WF) was prepared by grafting wood flour with phytic acid (PA) as the green modifier. The surface morphology, element distribution, functional group, specific surface area, crystallinity, crystal structure and porosity of PA-WF were characterized by scanning electron microscope-EDS energy spectrum, infrared spectrum, X-ray diffractometer, and BET. The effects of mass ratio of phytic acid to wood flour, mass ratio of urea to wood flour, reaction temperature and reaction time on the grafting rate of wood flour were explored. Firstly, the effects of PA-WF grafting ratios on the adsorption capacity of methylene blue dye solution were analyzed, and the changing law of PA-WF adsorption capacity under different adsorption time and initial concentration of methylene blue dye were further explored.

  Result  With the mass ratio of phytic acid to wood flour was 2.5 to 5, the mass ratio of urea to wood flour was 3 to 50, the reaction temperature of 70 ℃, and the reaction time of 3 h, modified wood flour with a grafting rate of 11.31% can be prepared. PA was successfully grafted on the wood flour to introduce phosphate groups and increase the specific surface area, mean pore size and pore volume of wood flour, which was showed in SEM-EDS, ATR-FTIR, XRD and BET research. The adsorption test results showed that PA-WF had the best adsorption performance when the grafting rate was 8%, and the adsorption capacity was 22.53 mg/g, which was 114.57% higher than that of unmodified wood flour (10.50 mg/g). The adsorption process of the PA-WF conformed to the Langmuir adsorption isotherm equation and the quasi-second-order kinetic equation.

  Conclusion  We use proper conditions to prepare phytic acid grafted modified wood flour. It is speculated that the adsorption process of adsorbent belongs to ion-exchange monolayer chemical adsorption. Using the anionic phosphate group in phytic acid can greatly improve the adsorption performance of wood flour, which provides a new idea for the high-value utilization of wood flour.