Decoupling the adsorption mechanisms of arsenate at molecular level on modified cube-shaped sponge loaded superparamagnetic iron oxide nanoparticles

In this study, a commercial cube-shaped open-celled cellulose sponge adsorbent was modified by in-situ co-precipitation of superparamagnetic iron oxide nanoparticles (SPION) and used to remove As(V) from aqueous solutions. Fe K-edge X-ray absorption spectroscopy (XAS) and TEM identified maghemite as the main iron phase of the SPION nanoparticles with an average size 13 nm. Batch adsorption experiments at 800 mg/L showed a 63% increase of adsorption capacity when loading 2.6 wt.% mass fraction of SPION in the cube-sponge. Experimental determination of the adsorption thermodynamic parameters indicated that the As(V) adsorption on the composite material is a spontaneous and exothermic process. As K-edge XAS results confirmed that the adsorption enhancement on the composite can be attributed to the nanoparticles loaded. In addition, adsorbed As(V) did not get reduced to more toxic As(III) and formed a binuclear corner-sharing complex with SPION. The advantageous cube-shape of the sponge-loaded SPION composite together with its high affinity and good adsorption capacity for As(V), good regeneration capability and the enhanced-diffusion attributed to its open-celled structure make this adsorbent a good candidate for industrial applications.     

基于HBPs接枝的PVDF膜亲水改性及抗污染性能

在聚偏氟乙烯（PVDF）微滤膜表面接枝超支化聚合物聚乙烯亚胺（HPEI）,并通过环氧丙醇与氨基的开环反应在PVDF膜表面形成高密度的多羟基结构,实现PVDF膜的亲水改性.实验对膜的表面亲水性、抗粘附性能和抗污染性能进行表征,并采用原子力显微镜（AFM）测量膜与污染物探针之间的粘附力以进一步探究改性膜的抗污染机理.实验结果显示,改性后,PVDF膜的接触角从85°减小至42°,润湿时间从20s缩短至10s,表面亲水性显著提高;在静态吸附实验中,改性膜表面粘附的蛋白质和多糖数量明显减少;在动态污染实验中,改性膜的水通量恢复率（FRR）较高,不可逆通量下降率（IFR）较低,说明其较强的抗污染性能.AFM界面粘附力的测试结果表明污染物探针与改性膜面的粘附力较弱,进一步证实改性膜表面丰富的亲水基团以及超支化结构的位阻效应可以有效改善PVDF膜的抗污染性能.     

NaOH改性鱼骨粉材料对Cd(II)的吸附

以鱼骨粉（FBM）为原料,利用NaOH处理制备高性能改性鱼骨粉材料（FBM_T）,通过比表面积仪（BET）、X射线衍射仪（XRD）、傅里叶红外光谱（FTIR）、扫描电镜-光电子能谱（SEM-EDS）、透射电镜（TEM）等手段对吸附前后材料形貌、孔结构、功能基团进行表征分析.结果表明,与FBM相比,FBM_T出现一定数目中孔和大孔,具备了高孔容和平均孔径,分别增加68.57%和24.69%.FBM_T材料表面-OH、C=O和PO₄^3-等官能团含量增加,显示出一定的缓冲性能.FBM和FBM_T对Cd（Ⅱ）的吸附经历快速的分配和慢速的吸附两个阶段,符合准二级动力学模型,相关系数R²分别达到0.8635及0.9480.Langmuir模型较好地拟合FBM和FBM_T对Cd（Ⅱ）的等温吸附过程,对Cd（Ⅱ）饱和吸附量由改性前的9.28mg/g增至改性后的22.47mg/g,对应的吸附强度K_F值也随之增加.分离因子0 < R_L < 1表明Cd（Ⅱ）的去除过程为有利吸附.功能材料与Cd（Ⅱ）的作用机理主要包括阳离子专性吸附、静电吸附、离子交换、表面络合及沉淀作用.以上研究为鱼骨粉修复Cd污染提供一种经济有效的方法.     

Thermodynamic prediction and experimental investigation of short-term dynamic membrane formation in dynamic membrane bioreactors: Effects of sludge properties

In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh(25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process(within 240 min). Furthermore, the extended Derjaguin–Landau–Verwey–Overbeek(XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process(including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time(permeate turbidity 1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability normal sludge sludge with poor flocculability. Moreover, normal sludge(regarding settleability, dewaterability,flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance(short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid–based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.     

Dynamic membrane bioreactor performance enhancement by powdered activated carbon addition: Evaluation of sludge morphological, aggregative and microbial properties

The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.     

高浓度液晶废水处理研究

针对某化工厂液晶中间体生产废水,采用Fenton预处理+水解酸化+好氧+超滤反渗透工艺进行处理,发现Fenton技术具有良好的预处理效果,对COD的去除率在50%左右,且废水可生化性从原水的0.05提高至0.38,经过水解酸化及好氧单元的降解,废水ρ(COD)可降至150~200 mg/L,再通过超滤反渗透膜处理,COD浓度可降至50mg/L以下,达到GB/T 19923—2005《城市污水再生利用—工业用水水质》要求,出水可用作稀释水或厂内冷却用水。膜浓水通过自主研发的强化蒸发装置处理,可实现废水不外排。采用该工艺对厂内实际生产废水进行现场调试运行,处理规模为5 m~3/d,原水初始pH值为2.0~4.5,ρ(COD)为7 000~10 000 mg/L。稳定运行后,生化段出水pH值为7.5~8.0;ρ(COD)为150~200 mg/L,膜处理后ρ(COD)<50 mg/L,证明运行稳定可靠。     

跨膜压差和膜面流速对磁絮凝延缓陶瓷微滤膜通量衰减的影响

为克服陶瓷微滤膜净化微污染水体时产水量不高、通量衰减迅速的难题,采用磁絮凝预处理工艺延缓陶瓷膜的污染。对比了磁絮凝预处理与传统絮凝预处理对陶瓷微滤膜膜污染的影响,结果显示:磁絮凝预处理后陶瓷膜的稳定产水量高于传统絮凝预处理,验证了磁絮凝预处理工艺延缓膜污染的可行性。同时,研究了跨膜压差和膜面流速对2种组合工艺膜通量的影响,结果表明:随着跨膜压差和膜面流速的增加,膜通量均提高但增幅逐渐放缓,其优化运行参数如下:跨膜压差为0.20 MPa,膜面流速为2.0 m/s。     

基于薄膜生物反应技术的环境污水处理方法研究

污水处理系统中使用传统污水处理技术会加入大量化学药品并且需要建立占地广阔的净化池,净化过程使用化学药品会存在一定的残留,针对上述问题,设计出基于薄膜生物反应技术的环境污水的处理方法.设计的方法由两部分组成一部分是膜分离单元一部分是生物处理单元.膜分离单元完成有毒物质以及漂浮物的隔离,通过MBR反应对污水中大分子有机物以及可溶性微生物进行反应消化,最终通过沉淀池的把多余的活性污泥进行沉淀完成污水的处理.为保证设计方法的有效性,按照设计方法模拟使用过程与传统污水处理方法进行对比,得出结论:(1)设计的基于薄膜生物反应技术的环境污水处理方法不需要对水中进行化学药品添加;(2)没有占用过多的净化空间;(3)在净水效果上明显比传统处理方法有效;(4)污水处理量大;(5)性价比较高节约污水处理成本.     

CSTR和MBR反应器的短程硝化快速启动

为实现短程硝化的快速启动,采用完全混合反应器(CSTR)和膜生物反应器(MBR)进行短程硝化启动性能对比研究,考察两个反应器在启动时间、氮素转化和污泥性能3个方面的差异.结果表明在进水C/N=1,温度为30℃±1℃,pH为7.5~8.0,DO为0.6~1.0 mg·L~(-1),结合缺氧/好氧比为1∶3(15 min∶45 min)和缩短HRT,CSTR和MBR分别运行56 d和44 d成功启动短程硝化,MBR启动周期较短.运行至第14 d、第28 d和第56 d时,CSTR和MBR亚硝累积率平均为51%、66%、89%和50%、71%、93%,硝酸盐氮生成速率(以NO_3~--N/MLVSS计)依次为7.4、4.0、1.7和7.6、3.5、1.0 mg·(g·h)~(-1),MBR在第28 d和第56 d表现出较高的亚硝累积率和较低的NO_3~--N产率,有利于短程硝化的快速启动.整个运行过程中,两个反应器内的亚硝化污泥均呈黄色,SVI在55~110 mL·g~(-1),MLVSS/MLSS稳定在0.6~0.8左右,良好的污泥性能为CSTR和MBR短程硝化的快速启动创造了有利条件.MBR在短程硝化快速启动中展现出更明显的优势.     

夏季高原河流CDOM光学特性、组成及来源研究

对高原河流有色溶解有机物(CDOM)光学特性、组成及来源进行研究,有利于更好的了解高原河流水体生态环境,为高原河流生态系统中溶解有机物(DOM)循环过程的研究提供数据参考.利用2017年夏季无定河和湟水流域河流的实测数据对CDOM的吸收特性、荧光特性、水质参数以及它们之间关系进行分析,进而对高原干旱地区河流CDOM光学特性及其组成与来源进行研究.研究结果表明:两流域河流中CDOM吸收系数随波长的增加呈衰减趋势,但吸收光谱曲线差别较大;两流域CDOM在440 nm处的吸收系数[a(440)]与溶解有机碳(DOC)具有显著相关性(p0.01),而与叶绿素a浓度(Chla)不存在相关性.无定河a(440)与Chla浓度的相关性说明其河流现场产生(生物活动)作用较小.通过对比分析S_(275-295)、SUVA_(254)发现,无定河分子量和芳香性程度均大于湟水,且湟水与无定河CDOM的分子量变化要高于其它河流的研究.根据CDOM三维荧光光谱分析发现,类腐殖质荧光峰是两流域河流CDOM荧光的主要贡献者;通过荧光指数FI、腐殖化指数HIX、生物源指数BIX的研究发现,湟水以陆源输入为主,腐殖化程度高,无定河以陆源输入为主的同时存在一定的自生成分,人为生产活动干扰是其陆源输入的主要影响因素.通过冗余分析发现,湟水DOC、Chla、pH对类腐殖质荧光峰及荧光强度影响较大(p0.01);无定河DOC、电导率(EC)、浊度(Tur)与类腐殖质荧光峰及荧光强度显著正相关(p0.01).