植酸改性木粉制备及其吸附性能研究

Preparation and adsorption property of phytic acid modified wood flour

【目的】将木材加工剩余物木粉和改性木粉作为废水中染料污染物的吸附剂,并探究其性能,为木粉高值化利用提供一种策略。【方法】以植酸(PA)为绿色改性剂接枝木粉制备了木粉基吸附剂(PA-WF),利用SEM–EDS、ATR–FTIR、XRD、BET对PA-WF的表面形貌、元素分布、官能团、孔隙度、比表面积、结晶度和结晶结构进行表征,分析了植酸和木粉质量比、尿素和木粉质量比、反应温度和反应时间对木粉接枝率的影响,以及不同接枝率木粉的亚甲基蓝染料溶液吸附容量,探究了PA-WF在不同吸附时间、亚甲基蓝染料不同初始质量浓度条件下的吸附容量变化规律。【结果】当植酸和木粉质量比2.5∶5、尿素和木粉质量比3∶50、反应温度70℃、反应时间3 h时,可制备接枝率为11.31%的改性木粉。SEM–EDS、ATR–FTIR、XRD和BET测试结果表明:PA成功接枝在木粉上引入磷酸基团,且增大了木粉的比表面积、平均孔径和孔体积。吸附测试结果表明:PA-WF在接枝率为8%时吸附性能最优,吸附容量可达22.53 mg/g,比未改性木粉的吸附容量(10.50 mg/g)提高了114.57%;PA-WF的吸附过程符合Langmuir吸附等温方程与准二级动力学方程。【结论】采用适当条件制备植酸接枝改性木粉,经推测其吸附过程属于离子交换的单分子层化学吸附。利用植酸中阴离子磷酸基团,可大幅提升木粉的吸附性能,为木粉的高值化利用提供新的思路。

[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.