A Review of the Fate and Effects of Silicones in the Environment

Silicones are well-known useful materials varying in structure, reactivity, and chemical and physical properties, but they all contain a covalent bond between the silicon atom and an organic group. Most common of these polymers are those based on polydimethylsiloxane (PDMS) having a siloxane (Si–O–Si) repeat unit and two methyl groups on each silicon atom. All these polymers are manmade, and the organosilicon linkage is not found in nature. It was therefore erroneously assumed that these polymers do not degrade naturally in the environment. It is the purpose of this review to refute this myth and to describe the degradation processes of PDMS in the environment and any potential ecological impact on the terrestrial, aquatic, and atmospheric compartments. Although it was found that minor degradation takes place by hydrolysis of PDMS to dimethylsilandiol followed by oxidation of the methyl group to aldehyde and ultimately to CO₂ by Arthobacter and Fusarium oxysporium schlechtendahl, the major degradation processes are abiotic. High molecular weight PDMS are initially depolymerized by soil hydrolysis of the siloxane bonds to yield organosilanol terminated oligomers. These organosilanols and low molecular weight linear PDMS and cyclics are evaporated into the atmosphere and are oxidized there by hydroxyl radicals to benign silica, water, and CO₂.     

水解与接触氧化工艺处理印染废水

印染废水采用混凝、水解酸化与接触氧化工艺进行处理，通过3个月的调试与运行，挂膜好，处理效果稳定，CODCr去除率在90％以上。     

碱解工艺预处理DMF废水

N,N-二甲基甲酰胺(DMF)及其分解产物二甲胺(DMA)对生物硝化具有强烈的抑制作用,致使含DMF废水的生物处理系统出水的氨氮质量浓度难以达到排放标准。为此,采用碱解预处理方法去除废水中的DMF和DMA。借助实验室小试装置优化了过程控制参数,再将此预处理方法运用到某DMF废水处理工程。小试结果表明,在加碱量为n(NaOH)∶n(DMF)=1.2∶1、反应压力为0.04 MPa、反应温度为76.0℃、反应时间为60 min的条件下,模拟废水的DMF质量浓度由10 000 mg/L降至35 mg/L,DMA质量浓度降至28 mg/L。DMF实际废水处理工程结果表明,经碱解预处理后,生物处理系统进水中DMF稳定在1.0 mg/L以下,DMA稳定在10 mg/L以下,出水氨氮质量浓度降至2.0 mg/L以下,生物硝化过程得以恢复。     

缫丝废液的综合利用

缫丝废液中含有丰富的蛋白质，直接排入严重污染环境，废液中的蛋白质能用化学或生物化学方面水解成有用的氨基酸，后者是化学，医药，食品，饲料工业的重要原料，本文报道了缫丝废液中蛋白质酸水解和酶水解的研究结果以及部分酶水解的规律。     

不同预处理方法对木薯渣水解效果的影响

目前木薯渣制沼气过程中面临预处理成本高,且预处理的催化剂大都会影响后续的厌氧发酵等难题。采用高温水热、稀HNO3高温催化2种处理方法分别对木薯渣进行水解,将木薯渣固相中的有机质转移到液相中,实现生物质的可溶化。结果表明,高温有利于木薯渣的水解,但同时造成水解液可生化性降低;稀HNO3的加入不仅对木薯渣水解起到催化促进作用,而且提高了水解液的可生化性,与水热水解相比,其BOD5/CODCr在150℃水解5min时从0.48升高到0.64。     

加压水解法处理含氰废水的研究

文章研究了含氰废水加压水解的反应条件及动力学,结果表明:水解温度影响最显著,反应时间次之,pH值及初始浓度影响都较小;氰化钾的加压水解反应规律符合一级反应动力学;在不同水解温度下,溶液中CN-加压水解的反应速率常数不同,并计算出该实验条件下的平均反应活化能。同时建立了氰化钾水解去除率与水解温度、反应时间的数学模型。     

碱处理促进剩余污泥解的试验研究

研究了热碱水解法对剩余污泥特性参数(溶解性化学需氧量、挥发性脂肪酸、氨氮、pH值与污泥浓度等)的影响.碱的加入减弱了污泥细胞壁对高温的抵抗力,加剧了剩余污泥细胞内有机质的释放与水解,改变了污泥的性质.在反应温度为170℃、pH 13、反应时间为75 min的条件下,溶解性化学需氧量(SCOD)达到了最大融出量17956 mg/L,此时SCOD与总化学需氧量(TCOD)之比为0.65.在pH 13,反应时间为60 min时悬浮固体(SS)、挥发性悬浮固体(VSS)均达到了最大溶解率,其值分别为67%和72%.经热碱水解处理后的剩余污泥SCOD随着原污泥浓度的增大而增大,呈现了良好的线性关系,相关系数R2达到了0.97以上,而且随着pH值的增大,融出率也不断增大,在pH 13时达到最高值672 mg/g.另外,通过正交试验可以得出170℃时各因素对SCOD影响的重要性,依次为污泥浓度、DH值、反应时间.     

Isolation and characterization of Sporobolomyces sp. LF1 capable of degrading chlorimuron-ethyl

A yeast strain which was capable of degrading sulfonylurea herbicide chlorimuron-ethyl named as LF1 was isolated from a chlorimuron-ethyl contaminated soil near the warehouse of the factory producing chlorimuron-ethyl in Shenyang City, Northeast China. The strain was identified as Sporobolomyces sp., based on its morphological and physiological characteristics and the phylogenetic analysis of 18S rRNA gene sequence. So far, this is the only yeast strain of Sporobolomyces sp. which is able to degrade chlorimuronethyl. Incubation tests showed that when the initial concentration of chlorimuron-ethyl in culture was 5 mg/L, LF1 could degrade more than 77% of the herbicide after incubation for 4 d at 30°C. The possible mechanism of chlorimuron-ethyl degradation by LF1 could be the acidic hydrolysis caused by the acids from the metabolism of the yeast strain. Further study should be conducted to examine the pathways of chlorimuron-ethyl degradation by LF1 and to approach the feasibility of using LF1 to degrade the chlorimuron-ethyl in soil system.     

焦磷酸镁的酸解及酸解产物的氨氮沉淀性能

针对磷酸铵镁热解过程中,生成焦磷酸镁的问题,开展了热解产物中焦磷酸镁的酸解研究,考察了pH值、温度、反应时间等对焦磷酸镁酸解行为的影响,得到焦磷酸根向正磷酸根的转化规律。研究表明通过酸解能有效地使不具备氨氮沉淀能力的焦磷酸镁转化为对氨氮具有高效沉淀作用的磷酸镁,从而实现磷酸铵镁的循环利用。研究还考察酸解产物的氨氮沉淀性能,包括pH值、投加量等对氨氮沉淀性能的影响。研究结果表明在适当的热解与酸解条件下,磷酸铵镁循环使用5次仍具有90%以上的氨氮脱出性能。     

高效负载型光催化剂制备及其加铂修饰技术

通过光催化氧化五氯苯酚钠实验,结合对催化剂晶型结构、比表面积的表征分析,优化钛酸四丁酯水解制备TiO₂负载型催化剂并加铂修饰的制备条件:R值、烧结温度、粘合剂添加量、空心玻璃珠粒径大小及催化剂中铂含量,从而制备出高效、实用的负载加铂修饰型半导体光催化剂.实验结果表明,当R=10,温度为650℃烧结1h,TiO₂∶硅酸钠∶空心玻璃珠=10∶2.5∶20(W),铂在催化剂中的重量百分比为1.4%～1.6%,空心玻璃珠的粒径为0.5mm时,所制备的加铂修饰负载型催化剂催化活性、使用寿命和牢固度均比较理想.用该催化剂做光催化实验,当反应液初始五氯苯酚钠浓度为100mg/L、pH值为6.5,催化剂投加量为2g/L,通氧气量为1.6mL/s,光照强度为30kW/m²时,五氯苯酚钠2 h光催化氧化率达92.0%.