Effects of phosphate on the transport of graphene oxide nanoparticles in saturated clean and iron oxide-coated sand columns

In this study, transport behaviors of graphene oxide (GO) in saturated uncoated (i.e., clean sand) and goethite-coated sand porous media were examined as a function of the phosphate. We found that phosphate enhanced the transport of GO over a wide range of solution chemistry (i.e., pH 5.0–9.0 and the presence of 10 mmol/L Na⁺ or 0.5 mmol/L Ca²⁺). The results were mainly ascribed to the increase of electrostatic repulsion between nanoparticles and porous media. Meanwhile, deposition site competition induced by the retained phosphate was another important mechanism leading to promote GO transport. Interestingly, when the phosphate concentration increased from 0.1 to 1.0 mmol/L, the transport-enhancement effect of phosphate in goethite-coated sand was to a much larger extent than that in clean sand. The observations were primarily related to the difference in the total mass of retained phosphate between the iron oxide-coated sand and clean sand columns, which resulted in different degrees of the electrostatic repulsion and competitive effect of phosphate. When the background solution contained 0.5 mmol/L Ca²⁺, phosphate could be bind to sand/ goethite-coated sand surface by cation bridging; and consequently, promoted competition between phosphate and nanoparticles for deposition sites, which was an important mechanism for the enhanced effect of phosphate. Moreover, the DLVO theory was applicable to describe GO transport behaviors in porous media in the absence or presence of phosphate. Taken together, these findings highlight the important status and role of phosphate on the transport and fate of colloidal graphene oxide in the subsurface environment.     

GO-TiO2改性PVDF复合膜去除微污染水体中氨氮

以氧化石墨烯（GO）、二氧化钛（TiO₂）和氧化石墨烯-二氧化钛（GO-TiO₂）为改性物质,借助真空过滤法对聚偏氟乙烯（PVDF）微滤膜进行改性制备复合膜.利用接触角测量仪、扫描电子显微镜、傅里叶红外变换光谱、X射线粉末衍射仪等手段探究了复合膜的结构和亲水性.同时选用腐殖酸（HA）作为水中微污染物的代表考察了复合膜的抗污染性能.选择常州滆湖支浜水样作为原水,研究了复合膜在黑暗及紫外光条件下对氨氮的去除效果.结果表明,GO、TiO₂和GO-TiO₂（GT）复合膜均具有优于PVDF膜的亲水性和抗污染性能,黑暗条件下,GO浓度为1mg/mL的GO复合膜氨氮去除率最高,达到26.4%;紫外光条件下,GO和TiO₂间存在协同作用,GO-TiO₂浓度为1mg/mL、GO/TiO₂=3：1的GT复合膜氨氮去除效率达到最佳（58.2%）.     

Fe3O4/GO对水溶液中Cd(II)去除的影响因素

为探索高效且快速去除水溶液中Cd （Ⅱ）污染方法,采用自制磁性四氧化三铁负载氧化石墨烯（Fe₃O₄/GO）纳米复合材料对水溶液中Cd （Ⅱ）进行去除,利用单因素实验确定影响因素水平范围（初始Cd （Ⅱ）浓度、温度、反应时间、初始pH值）,并采用响应面法（RSM）及人工神经网络-遗传算法（ANN-GA）对去除水溶液中Cd （Ⅱ）的影响因素（4因素3水平）进行优化,利用等温吸附、动力学及热力学参数研究吸附剂性能.通过扫描电子显微镜（SEM）、X射线衍射仪及超导量子干涉器件（SQUID）对复合材料表征.结果表明,平均粒径为30.9nm的磁性Fe₃O₄/GO纳米复合材料被成功制备.RSM用于磁性Fe₃O₄/GO纳米复合材料对水溶液中Cd （Ⅱ）去除条件优化,预测去除率达到86.451%,验证试验为82.220%,对应条件：温度为20.14℃,反应时间为57.78min,初始pH值为6.41和初始Cd （Ⅱ）浓度为11.18mg/L; ANN-GA优化条件后的预测去除率为89.722%,验证试验为87.723%,相应条件：温度为29.96℃,pH值为5.49,初始Cd （Ⅱ）浓度为28.36mg/L,反应时间为65.78min.根据模型R²值,预测的最大去除率及验证试验,ANN-GA模型性能及预测能力均高于RSM.RSM方差分析表明4个因素对磁性Fe₃O₄/GO纳米复合材料去除水溶液中Cd （Ⅱ）的影响大小为：初始Cd （Ⅱ）浓度>温度>反应时间>pH值.吸附机理分析结果显示,Fe₃O₄/GO纳米复合材料对Cd （Ⅱ）吸附过程同时存在着物理吸附和化学吸附.结合ANN-GA优化,利用磁铁实现且快速分离,磁性Fe₃O₄/GO纳米复合材料用于去除Cd （Ⅱ）是可行的.关键字：Cd （Ⅱ）;四氧化三铁负载氧化石墨烯;单因素实验;响应面法;人工神经网络-遗传算法中图分类号：X53     

锰铝双氧化物改性生物炭减缓土壤重金属对黑麦草的毒性作用

电子垃圾拆解过程中引起的土壤重金属铜(Cu)和镉(Cd)复合污染现象成为一个严峻的问题,为了解决这一问题,利用废弃的螃蟹壳生物质与锰铝盐进行共沉淀后共热解制备了螃蟹壳生物炭(BC)和片状锰铝双氧化物改性的螃蟹壳生物炭(LDO/BC)材料.污染土壤经过BC和LDO/BC修复后,土壤pH、有效磷、速效钾和酶活性得到了提升,土壤中的DTPA-Cu和DTPA-Cd含量显著降低.微生物群落分析表明BC-1%能促进Gemmatimonadota(芽单胞菌)和Acidobacteriota(酸杆菌)相对丰度的上升,而LDO/BC-1%能促进Proteobacteria(变形菌)相对丰度的上升,且变形菌有利于减少Cd在植物中的积累作用.在修复后的土壤中种植黑麦草培养28 d,结果表明,经过投加量为5%BC和1%LDO/BC分别修复后土壤种植的黑麦草发芽率分别提高29%和60%,生长状况更佳,并且黑麦草植株内Cu和Cd的含量相对于未经生物炭材料处理的空白组显著降低.LDO/BC-1%处理组相对于其他处理组表现出更优异的修复效果,且负载在LDO/BC上的Mn可以有效地降低黑麦草吸收土壤中的重金属Cd.     

酸性矿山废水中锰氧化菌的分离鉴定及其对Mn2+的去除作用

含锰（Mn）重金属废水的处理是行业痛点与难点,近年来高效的生物脱锰技术得到广泛关注,但具有较高锰氧化效率菌株的报道仍然有限.本研究从酸性矿山废水中分离纯化出一株锰氧化细菌,并深入探究其微生物特性以及对Mn²⁺的去除作用.通过生理生化及16S rRNA序列分析鉴定该菌株为短芽孢杆菌,并命名为Brevibacillus brevis MM2.进一步通过单因素实验探究了环境因子和初始锰浓度对菌株MM2的生长和锰去除率的影响.结果表明,菌株MM2对Mn²⁺的最高耐受浓度可达1000 mg·L^-1,且在弱酸条件下（pH 6、pH 5）仍然显现出良好的生长趋势,具有较高的锰去除率（91.93%,pH=6）.此外,菌株MM2在 30~35 ℃,pH 7,转速180 r·min^-1条件下生长趋势最好,当初始Mn²⁺浓度为100 mg·L^-1时,Mn²⁺的最高去除率为92.76%.最后,通过扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、X射线衍射（XRD）、傅里叶红外光谱仪（FTIR）对代谢固相产物分析表明,菌株MM2介导生成的生物氧化锰附着在菌株表面并以层状和颗粒状两种形态呈现,锰平均氧化度为3.55,其成分主要为无定形的Mn₂O₃和MnO₂.综上所述,本研究分离纯化的菌株MM2不仅能在弱酸性条件下生长且对锰具有较高的耐受和去除能力,在含锰废水的处理中具有较好应用前景.     

Release of Pb adsorbed on graphene oxide surfaces under conditions of Shewanella putrefaciens metabolism

In this study, Pb(II) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens (S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on lead that was preadsorbed on graphene oxide (GO) surfaces. The results showed that GO was transformed to its reduced form (r-GO) by bacteria, and this process induced the release of Pb(II) adsorbed on the GO surfaces. After 72 hr of exposure in an S. putrefaciens system, 5.76% of the total adsorbed Pb(II) was stably dispersed in solution in the form of a Pb(II)-extracellular polymer substance (EPS) complex, while another portion of Pb(II) released from GO-Pb(II) was observed as lead phosphate hydroxide (Pb₁₀(PO₄)₆(OH)₂) precipitates or adsorbed species on the surface of the cell. Additionally, increasing pH induced the stripping of oxidative debris (OD) and elevated the content of dispersible Pb(II) in aqueous solution under the conditions of S. putrefaciens metabolism. These research results provide valuable information regarding the migration of heavy metals adsorbed on GO under reducing conditions due to microbial metabolism.     

Determination of 2,4-Dichlorophenoxyacetic acid in food and water samples using a modified graphene oxide sorbent and high-performance liquid chromatography

Abstract

In the present work, dispersive micro-solid phase extraction (D-μ-SPE) method using magnetic graphene oxide tert-butylamine (GO/Fe₃O₄/TBA) nanocomposite, as an efficient sorbent, was applied for determining 2,4-dichlorophenoxyacetic acid (2,4-D) in water and food samples. Detection was carried out using high-performance liquid chromatography (HPLC) instrument. Influential parameters of D-μ-SPE such as sorbent and its amount, elution solvent and its volume, adsorption and desorption times and pH of sample solution were investigated and optimized. Under the optimized conditions, limit of detection and quantitation values were 0.007 and 0.02?μg/mL, respectively. Recovery data for several real samples were obtained within the range of 88.0–94.0% with a relative standard deviation (RSD) less than 7.5%. The proposed method was successfully applied to quantitative determination of 2,4-D in several vegetables and water samples.     

生石灰对福寿螺的毒性效应研究

通过室内毒性试验,探索了生石灰对不同大小福寿螺的毒性效应。试验中将福寿螺按照壳高（H）分为小螺（5 mm≤H〈15 mm）、中螺（15 mm≤H〈25 mm）、大螺（25 mm≤H〈35 mm）和超大螺（35 mm≤H〈45 mm）,结果表明：（1）生石灰的控螺效应显著,尤其是对中小福寿螺具很强的抑制和杀灭作用;生石灰处理6 d,除了最低质量浓度0.05 g.L-1处理造成35%死亡率,其他处理死亡率均在70%以上,其中0.20、0.50、1.00和2.00 g.L-1处理中超过90%的福寿螺死亡。（2）生石灰对不同大小福寿螺的半抑制质量浓度（24 h）大小顺序为超大螺〉中螺、大螺〉小螺,半致死质量浓度（24 h）大小顺序为超大螺〉大螺〉中螺〉小螺;（3）生石灰对福寿螺的毒性以抑制效应为主,生石灰对福寿螺的平均半抑制质量浓度为0.06～0.22 g.L-1,低于平均半致死质量浓度0.11～1.09 g.L-1;（4）0.50 g.L-1和2.00 g.L-1质量浓度的石灰处理12 h后,福寿螺鰓组织SOD酶活性呈极显著下降,分别为对照的33%和38%。研究表明,生石灰可用于防治入侵生物福寿螺,在实践中可部分替代杀螺剂的使用。     

Bromobenzene-induced hepatotoxicity in male rats: the protective effect of flaxseed

The metabolites of bromobenzene (BB) are hepatotoxic. The aim of this study was to determine the efficacy of different doses of flaxseed extract in alleviating BB-hepatotoxicity in male albino rats. Oxidative stress parameters, drug metabolizing enzymes, a pro-inflammatory marker, an apoptotic marker, and DNA fragmentation pattern were also assessed. Animals were divided into five groups treated by intragastric intubation as follows: control, BB-treated 460?mg?kg^?1?BW alone; three animal groups (III, IV, V) were treated concurrently with 460?mg?kg^?1 BB daily for 3 weeks and different doses of flaxseeds extract: 100, 200, or 300?mg?kg^?1?BW. Oral treatment of BB produced a significant decrease in activities of antioxidant enzymes superoxide dismutase and glutathione peroxidase and glutathione levels, while activities of glutathione reductase and drug-metabolizing enzymes; glutathione-S-transferases and cytochrome P450 were enhanced. BB-treatment resulted in enhanced production of nitric oxide and activation of COX-2 and caspase-3. Pre-treatment with different doses of flaxseeds extract prior and during BB-treatment protected liver against BB-induced hepatotoxicity. The lower dose of flaxseed extract (100?mg?kg^?1) was most effective one.