改性稻秆阴离子吸附剂的制备及对硝酸根吸附研究

Preparation for modified rice straw anionic adsorbent and its adsorption on nitrate

NO_3^-对水环境是污染物,对土壤而言则是肥料,因此NO_3^-高效吸附剂的研发对于水环境治理和土壤保肥均有重要意义。以废弃稻秆为原料,结合物理、化学改性手段制备出稻秆(RS)、生物炭稻秆(RS-B)、乙二胺稻秆(DMF-RS)和乙二胺生物炭稻秆(DMF-RS-B) 4种NO_3^-吸附剂,通过SEM和FTIR等方法表征其表面特性和官能团特性确定改性情况,对比4种吸附剂对NO_3^-的去除效果和有机碳源溶出量。结果表明,4种吸附剂中DMF-RS-B对NO_3^-的去除效果最好。在NO_3^-初始质量浓度为30 mg/L,吸附剂投加量为4g/L,pH=2,吸附时间为10 min时,其最大去除率可达61. 22%,表观吸附量达15. 31 mg/g。吸附剂对NO_3^-的吸附过程符合D-R吸附等温方程(R^2> 0. 99),吸附过程为多分子层吸附且是自发放热过程。通过实际水样测试,DMF-RSB对NO_3^-的吸附效果显著,且出水无二次污染。本吸附剂亦可作为缓释固相碳源及土壤保肥(氮肥)材料,是绿色无污染的吸附剂。

The given paper is inclined to present a kind of highly efficient adsorbent for nitrate in helping to improve the water environment control and soil conservation system with the physical and chemical methods(that is by using the rice straw(RS),the biochar-rice straw(RS-B),ethylenediamine-rice straw(DMFRS),and the ethylenediamine-biochar-rice straw(DMF-RS-B).As a matter of fact,nitrate is a pollutant to the water environmentbut a fertilizer to the soil.Therefore,it is necessary to verify the condition of the modified material and the adsorptive mechanism to determine the oxygen functional groups on the adsorbent surface before and after the necessary modification by SEM and FTIR.For the above said purpose,we have investigated the effects of the different modification methods,the solution’s dosage and the pH value on the removal of NO3-by different modified adsorbents.In so doing,we have examined and identified the mechanism of NO3-removal by the adsorbent through the isothermal adsorption equilibrium and adsorption thermodynamics.At the same time,we have also compared the dissolution rates of the organic carbon sources of the 4 adsorbents.The experimental results we have gained in this paper have shown that:DMF-RS-B should be the best adsorbent with 61.22%of 15.31 mg/g under the initiating nitrate nitrogen concentration of 30 mg/L,in a dosage of 4 g/L with the pH value of 2 for the 10 minutes.The experimental results also indicate that it is also possible for the removal process of nitrate with the DMF-RS-B to be described properly via the Dubinin-Redushkevich model with its correlation coefficient being over 0.99 correspondingly.What is more,the main adsorption process can also be described as and categorized into those of chemical reactions,suggesting that it belongs to a multi-molecule layer and self-releasing thermos process,whereas the effect of DMF-RS-B on NO3-should be of great significance for the simulated sewage,with no further pollution to be released.In addition,the adsorbent of the modified material may enjoy a wide application prospect in the sewage treatment.The adsorbent of the modified material can be also used as a kind of solid carbon source and soil fertilizer.It can be used as a green adsorbent as well.