生物炭-类水滑石强化混凝处理猪场尾水及其机理分析

以皇竹草秸秆为原料制备生物炭,通过生物炭-Mg Fe类水滑石强化混凝处理经二级生化处理的猪场尾水,研究其处理效果,用X射线衍射(XRD)、傅立叶变换红外(FTIR)、扫描电镜-能谱分析(SEM-Mapping)技术分析混凝沉淀物,以分析污染物去除机理。结果表明,在p H=8.45、Mg与Fe物质的量比(n(Mg)∶n(Fe))为2.8∶1的条件下,皇竹草生物炭-Mg Fe类水滑石混凝法对猪场尾水中浊度、COD和TP的处理效果较好,而对TN和NH+4-N去除率较低。生物炭投加量对猪场尾水中浊度和TP的处理影响不大,但对COD去除影响较为显著。生物炭-Mg Fe类水滑石强化混凝高效去除COD的机理主要为胶体状天然有机物的电中和作用和吸附于金属氢氧化物表面上的共沉淀作用;高效除磷的机理是在混凝过程中,磷酸盐通过自组装进入类水滑石层间,以及磷酸盐与Fe3+反应形成磷酸铁矿物。

Advanced treatment of pig-feeding left-over sewage through enhanced coagulation with biochar-MgFe layered double hydroxides via probe into its mechanism

The paper is inclined to find a new approach to the second-stage biochemical treatment of the pig-feeding left-over sewage due to the fact that there still remain high-concentrated contaminants.For this purpose,we have prepared straw biochar from the Pennisetum sinese Roxb and taken it as the adsorbent in the aforementioned sewage treating process for the enhanced coagulation with MgFe double-layered hydroxides.To identify the mechanism of the pollutants removal,we have collected and analyzed coagulation precipitants via the X-ray diffraction (XRD),the Fourier transform infrared spectroscopy (FTIR) and the electronic microscope scanning-map (i.e.the SEM-Mapping) technology.The results of our experiment show that,when the initial pH value is 8.45 with the Mg-Fe molar ratio being 2.8 ∶ 1,it is possible to reach higher removal rates of the turbidity,COD and TP,though the efficiency for NH4+-N and TN removal remains unsatisfied.Such an unpleasant condition pushed us to make an effort to enhance the coagulation by using the magnetized iron mixed metal solution and biochar,yet,little effect can be seen by changing the biochar dosage on the removal of the turbidity and TP,though it can bring about remarkable effect on their removal.Thus,the results of XRD indicate that the iron phosphate can be formed by the self-assembhng reaction and intercalation into the MgFe-layered double hydroxides.Furthermore,the absorption peaks of the carbonate and phosphate have been found well in accord with the result of FTIR.In addition,the SEM-mapping results of the coagulation sludge also prove that carbon,iron and phosphorus can be obviously seen,but nitrogen can hardly be found at all.At this,we have noticed that the chief mechanism of high removal rate of COD lies in the neutralized charge of the colloidal organic pollutants and co-precipitation of the organic pollutants with the double-layered hydroxides.The myth of the efficient removal of phosphorus lies in that phosphate can help to assemble the interlayers of the MgFe-layered double hydroxides with the reaction of phosphate and Fe3+ being able to generate iron phosphate minerals.Thus,it can be concluded that the enhanced coagulation with biochar-MgFe layered double hydroxides can help to remove phosphorus,COD and turbidity effectively,which suggests a novel approach to the in-depth treatment of sewage in the livestock husbandry.