NaOH改性玉米秸秆强化尾水脱氮特性研究

Characterization of NaOH modified corn straw and its application to nitrogen removal of tail water

对玉米秸秆进行NaOH改性,初步揭示了NaOH改性对玉米秸秆的作用机制,以期为玉米秸秆用于强化污水厂尾水反硝化脱氮提供理论依据。研究了NaOH用量对预处理前后释碳规律和红外光谱特征的影响,确定了适宜的预处理碱浓度;并进一步对NaOH预处理后的玉米秸秆生物质碳源进行物质组成、微观结构和脱氮效果研究。结果表明,NaOH预处理能够有效提高有机质释放量。红外光谱(FT-IR)结果表明当碱液质量分数达到2%时,纤维素分子间发生有序性重排,结晶度增加。玉米秸秆经过质量分数为2%的NaOH预处理后,其木质素被破坏,内部半纤维素含量减少,同时杂质和灰分也被有效去除,纤维素含量的占比提高了12%。NaOH预处理不但可以破坏小分子环烃的环状结构,同时也能提高基质表层附着力,投加NaOH改性玉米秸秆生物质的系统在1 h内硝酸盐氮脱除率达到71.8%,48h后几乎全部脱除。NaOH改性玉米秸秆有效提高了系统脱氮效率,并且具备尾水处理附加成本低、环境友好等优势。因此,经NaOH改性后的玉米秸秆是一种适宜的尾水脱氮外加生物质碳源。

The research and development of deep denitrification technology for tail water in urban sewage treatment plants has always been a difficult point and hotspot in the field of water treatment research.As a new carbon source,the use of cellulose carbon source for deep denitrification of tail water in urban wastewater plants not only achieves effective removal of residual nitrogen in tail water,but also helps to solve the waste of agricultural waste resources.In this study,corn straw was modified with NaOH in order to improve the efficiency of tail water treatment with modified corn straw.The effect of NaOH concentrations on the carbon release with corn straw was investigated and the appropriate alkali concentration for the pretreatment was determined.NaOH modified corn straw was further characterized by Van Soest method,gas chromatograph-mass spectrometer(GC-MS),scanning electron microscope(SEM),and FT-IR.To study the effect of carbon source on denitrification,the concentration of nitrate nitrogen in the conical flask was studied with a constant temperature oscillator.The results showed the release of organic matter increased after the NaOH pretreatment.FT-IR results showed that orderly rearrangement occurred between the cellulose molecules,and the degree of crystallinity increased when the alkali mass ratio reached 2%.The lignin of corn straw was destroyed and the hemicellulose content was reduced after 2% NaOH pretreatment.The pretreatment also effectively removed impurities and the percentage of cellulose content in corn straw increased by 12%.NaOH modification improved the adhesion of the substrate surface.Large amount of nitrate nitrogen(71.8%)was removed within one hour when using alkali treated corn straw for the tail water treatment,and almost all of them were removed when the treatment time prolonged to 48 hours.NaOH modified corn straw could lower the process cost in tail water treatment for urban wastewater treatment plants.It is a suitable source of carbon to enhance the nitrogen removal from tail water.