Bio-remediation of acephate–Pb(II) compound contaminants by Bacillus subtilis FZUL-33

Removal of Pb~(2+)and biodegradation of organophosphorus have been both widely investigated respectively. However, bio-remediation of both Pb~(2+)and organophosphorus still remains largely unexplored. Bacillus subtilis FZUL-33, which was isolated from the sediment of a lake, possesses the capability for both biomineralization of Pb~(2+)and biodegradation of acephate. In the present study, both Pb~(2+)and acephate were simultaneously removed via biodegradation and biomineralization in aqueous solutions.Batch experiments were conducted to study the influence of p H, interaction time and Pb~(2+)concentration on the process of removal of Pb2+. At the temperature of 25°C, the maximum removal of Pb~(2+)by B. subtilis FZUL-33 was 381.31 ± 11.46 mg/g under the conditions of p H 5.5, initial Pb~(2+)concentration of 1300 mg/L, and contact time of 10 min. Batch experiments were conducted to study the influence of acephate on removal of Pb~(2+)and the influence of Pb2+on biodegradation of acephate by B. subtilis FZUL-33. In the mixed system of acephate–Pb2+, the results show that biodegradation of acephate by B. subtilis FZUL-33 released PO43+, which promotes mineralization of Pb2+. The process of biodegradation of acephate was affected slightly when the concentration of Pb2+was below 100 mg/L. Based on the results, it can be inferred that the B. subtilis FZUL-33 plays a significant role in bio-remediation of organophosphorus-heavy metal compound contamination.     

Using a novel adsorbent macrocyclic compound cucurbit[8]uril for Pb removal from aqueous solution

In this study, cucurbit[8]uril (CB[8]) was utilized as a kind of new adsorbent to remove Pb^2 + ions from aqueous solution. With the solution pH increased from 2 to 6, the removal efficiency of adsorption increased from 55.6% to 74.5%correspondingly. The uptake of Pb^2 + increased rapidly in the initial 30 min, and then the adsorption rate became slower. The Pseudo-second order model could be used to interpret the adsorption kinetics satisfactorily; and the rate determining step in Pb^2 + adsorption onto CB[8] was the external mass transfer step. Equilibrium isotherm study reveals that the Langmuir model gave a better fitting result than Freundlich model. The maximum adsorption capacity calculated by the Langmuir model was 152.67 mg/g for 298 K, 149.70 mg/g for 313 K and 136.42 mg/g for 323 K, respectively. The adsorption is a spontaneous process of exothermic nature. The effect of the adsorbent dosage and the influences of solution pH and co-existing cations were also investigated. The CB[8] was synthesized and characterized by ¹H NMR, IR, ESI-MS spectra, SEM-EDAX, Zeta-potential and BET-analysis. The adsorption mechanism was due to the coordination between CB[8] molecule and Pb^2 + ions.     

The biological effect of metal ions on the granulation of aerobic granular activated sludge

As a special biofilm structure, microbial attachment is believed to play an important role in the granulation of aerobic granular activated sludge (AGAS). This experiment was to investigate the biological effect of Ca^2 +, Mg^2 +, Cu^2 +, Fe^2 +, Zn^2 +, and K⁺ which are the most common ions present in biological wastewater treatment systems, on the microbial attachment of AGAS and flocculent activated sludge (FAS), from which AGAS is always derived, in order to provide a new strategy for the rapid cultivation and stability control of AGAS. The result showed that attachment biomass of AGAS was about 300% higher than that of FAS without the addition of metal ions. Different metal ions had different effects on the process of microbial attachment. FAS and AGAS reacted differently to the metal ions as well, and in fact, AGAS was more sensitive to the metal ions. Specifically, Ca^2 +, Mg^2 +, and K⁺ could increase the microbial attachment ability of both AGAS and FAS under appropriate concentrations, Cu^2 +, Fe^2 +, and Zn^2 + were also beneficial to the microbial attachment of FAS at low concentrations, but Cu^2 +, Fe^2 +, and Zn^2 + greatly inhibited the attachment process of AGAS even at extremely low concentrations. In addition, the acylated homoserine lactone (AHL)-based quorum sensing system, the content of extracellular polymeric substances and the relative hydrophobicity of the sludges were greatly influenced by metal ions. As all these parameters had close relationships with the microbial attachment process, the microbial attachment may be affected by changes of these parameters.     

新型钛酸钠填料对Cu2+、Pb2+、Zn2+和Cd2+的竞争吸附研究

以钛酸钠纳米纤维为原材料制备新型钛酸钠填料,对水体中常见的重金属(Cu~(2+)、Pb~(2+)、Zn~(2+)和Cd~(2+))进行竞争吸附实验研究,分析了四元、三元及双组分竞争吸附的选择性吸附特性,并探讨了4种金属离子在钛酸钠填料上的相互作用关系.结果显示,初始浓度较低时,4种离子之间的相互影响差异性不明显;随着初始浓度的升高,4种离子的竞争吸附分配系数都呈下降的趋势,竞争吸附系数大小顺序为:Pb~(2+)Cu~(2+)Zn~(2+)Cd~(2+),这与重金属离子的第一水解常数大小顺序一致.竞争吸附结果表明,水中存在Pb~(2+)时,其余3种离子的吸附都会被抑制,尤其对Zn~(2+)和Cd~(2+)的抑制更显著,即在钛酸钠填料上Pb~(2+)的竞争吸附能力最强,Cu~(2+)次之,而Zn~(2+)和Cd~(2+)的竞争吸附能力较弱,其吸附过程容易受到其他二价金属离子的抑制.     

Zeolite A synthesized from alkaline assisted pre-activated halloysite for efficient heavy metal removal in polluted river water and industrial wastewater

High quality zeolite A was synthesized through a hydrothermal process using alkaline-assisted pre-activated halloysite mineral as the alumina and silica source. The synthesis conditions employed in this study were finely tuned by varying the activating temperature, sodium hydroxide content, water content and Si/Al ratio. The obtained zeolite A showed excellent adsorption properties for both single metal cation solutions and mixed cation solutions when the concentrations of the mixed cations were comparable with those in polluted natural river water and industrial wastewater. High adsorptive capacities for Ag⁺ (123.05 mg/g) and Pb^2 + (227.70 mg/g) were achieved using the synthesized zeolite A. This observation indicates that the zeolite A synthesized from alkaline-assisted pre-activated halloysite can be used as a low-cost and relatively effective adsorbent to purify heavy metal cation polluted natural river water and industrial wastewater.     

Effects of metal ions on the catalytic degradation of dicofol by cellulase

A new technique whereby cellulase immobilized on aminated silica was applied to catalyze the degradation of dicofol, an organochlorine pesticide. In order to evaluate the performance of free and immobilized cellulase, experiments were carried out to measure the degradation efficiency. The Michaelis constant, K_m, of the reaction catalyzed by immobilized cellulase was 9.16 mg/L, and the maximum reaction rate, V_max, was 0.40 mg/L/min, while that of free cellulase was K_m = 8.18 mg/L, and V_max = 0.79 mg/L/min, respectively. The kinetic constants of catalytic degradation were calculated to estimate substrate affinity. Considering that metal ions may affect enzyme activity, the effects of different metal ions on the catalytic degradation efficiency were explored. The results showed that the substrate affinity decreased after immobilization. Monovalent metal ions had no effect on the reaction, while divalent metal ions had either positive or inhibitory effects, including activation by Mn^2 +, reversible competition with Cd^2 +, and irreversible inhibition by Pb^2 +. Ca^2 + promoted the catalytic degradation of dicofol at low concentrations, but inhibited it at high concentrations. Compared with free cellulase, immobilized cellulase was affected less by metal ions. This work provided a basis for further studies on the co-occurrence of endocrine-disrupting chemicals and heavy metal ions in the environment.     

Modeling of acute cadmium toxicity in solution to barley root elongation using biotic ligand model theory

Protons（H⁺）as well as different major and trace elements may inhibit cadmium（Cd）uptake in aquatic organisms and thus alleviate Cd toxicity.However,little is known about such interactions in soil organisms.In this study,the independent effects of the cations calcium(Ca²⁺),magnesium(Mg²⁺),potassium（K⁺）,H+and zinc(Zn²⁺)on Cd toxicity were investigated with 5-day long barley root elongation tests in nutrient solutions.The tested concentrations of selected cations and trace metal ions were based on the ranges that occur naturally in soil pore water.The toxicity of Cd decreased with increasing activity of Ca²⁺,Mg²⁺,H⁺and Zn²⁺,but not K⁺.Accordingly,conditional binding constants were obtained for the binding of Cd²⁺,Ca²⁺,Mg²⁺,H⁺,and Zn²⁺ with the binding ligand:log K_CdBL5.19,logK_CaBL2.87,logK_MgBL2.98,logK_HBL5.13 and logK_ZnBL5.42,respectively.Furthermore,it was calculated that on average 29% of the biotic ligand sites needed to be occupied by Cd to induce a 50% decrease in root elongation.Using the estimated constants,a biotic ligand model was successfully developed to predict the Cd toxicity to barley root elongation as a function of solution characteristics.The feasibility and accuracy of its application for predicting Cd toxicity in soils were discussed.     

Evaluation of the adsorptive capacity of peanut hull pellets for heavy metals in solution

This study assessed the potential of peanut hull pellets to capture metal ions from wastewater and compared their performance to that of raw peanut hulls and a commercial grade ion-exchange resin. The uptake of Cu²⁺, Cd²⁺, Zn²⁺, and Pb²⁺ onto these media was investigated using a system of standardized batch adsorbers under steady state and transient rate conditions. The influence of the pelletizing process on the rate of metal ion sorption was evaluated by comparing the rate and extent of metal ion uptake onto peanut hull pellets vs. raw peanut hulls. Although a slight reduction in rate of adsorption was apparent for metal ion adsorption onto the pellets, equilibrium capacity was unaffected. Peanut hull pellets are an effective adsorbent for metal ion removal. Though their capacity is lower than that of commercial grade ion-exchange resins, their low cost makes them an attractive option for the treatment of low-strength metal ion waste streams in once-through fixed bed applications.     

Application of internal standard method in recombinant luminescent bacteria test

Mercury and its organic compounds have been of severe concern worldwide due to their damage to the ecosystem and human health. The development of effective and affordable technology to monitor and signal the presence of bioavailable mercury is an urgent need. The Mer gene is a mercury-responsive resistant gene, and a mercury-sensing recombinant luminescent bacterium using the Mer gene was constructed in this study. The mer operon from marine Pseudomonas putida strain SP1 was amplified and fused with prompterless luxCDABE in the pUCD615 plasmid within Escherichia coli cells, resulting in pTHE30–E. coli. The recombinant strain showed high sensitivity and specificity. The detection limit of Hg^2 + was 5 nmol/L, and distinct luminescence could be detected in 30 min. Cd^2 +, Cu^2 +, Zn^2 +, Ca^2 +, Pb^2 +, Mg^2 +, Mn^2 +, and Al^3 + did not interfere with the detection over a range of 10^− 5–1 mM. Application of recombinant luminescent bacteria testing in environmental samples has been a controversial issue: especially for metal-sensing recombinant strains, false negatives caused by high cytotoxicity are one of the most important issues when applying recombinant luminescent bacteria in biomonitoring of heavy metals. In this study, by establishing an internal standard approach, the false negative problem was overcome; furthermore, the method can also help to estimate the suspected mercury concentration, which ensures high detection sensitivity of bioavailable Hg^2 +.     

镁改性硅藻土回收废水氮磷产物对水中Pb2+和Zn2+的去除

通过使用镁改性硅藻土回收废水中的氮磷营养素,优化制备了一种复合材料（D-MAP）,并将其用于废水中重金属Pb²⁺和Zn²⁺的去除.研究探讨了材料投加量、反应时间、反应温度和溶液初始pH等因素对Pb²⁺和Zn²⁺在D-MAP上吸附的影响.D-MAP吸附去除Pb²⁺和Zn²⁺的最优条件为：D-MAP投加量分别为0.25 g·L^-1和0.30 g·L^-1,Pb²⁺和Zn²⁺初始浓度分别为300 mg·L^-1和60 mg·L^-1,溶液初始pH为5.0.在此条件下,其对Pb²⁺和Zn²⁺去除率分别可达78.67%和89.66%.动力学和热力学的结果表明,D-MAP对Pb²⁺和Zn²⁺的吸附更符合准二级动力学模型;其吸附等温线可用Langmuir模型描述,吸附是自发吸热的过程.Langmuir等温拟合结果指出,D-MAP对Pb²⁺和Zn²⁺的最大吸附容量分别为901.0 mg·g^-1和206.2 mg·g^-1.使用SEM/EDS、XRD和FT-IR等手段对吸附Pb²⁺和Zn²⁺前后的吸附剂进行表征,结果表明,D-MAP是一种鸟粪石-硅藻土复合材料,可通过与Pb²⁺和Zn²⁺生成Pb₁₀（PO₄）₆（OH）₂和Zn₃（PO₄）₂·2H₂ O去除废水中Pb²⁺和Zn²⁺.D-MAP对Pb²⁺和Zn²⁺的去除效果随着pH的增加而增加,且最终产物形态随pH不同产生变化.     

Enhanced catalytic complete oxidation of 1,2-dichloroethane over mesoporous transition metal-doped γ-Al2O3

High-surface-area mesoprous powders of γ-Al₂O₃ doped with Cu^2 +, Cr^3 +, and V^3 + ions were prepared via a modified sol–gel method and were investigated as catalysts for the oxidation of chlorinated organic compounds. The composites retained high surface areas and pore volumes comparable with those of undoped γ-Al₂O₃ and the presence of the transition metal ions enhanced their surface acidic properties. The catalytic activity of the prepared catalysts in the oxidation of 1,2-dichloroethane (DCE) was studied in the temperature range of 250–400°C. The catalytic activity and product selectivity were strongly dependent on the presence and the type of dopant ion. While Cu^2 +- and Cr^3 +-containing catalysts showed 100% conversion at 300°C and 350°C, V^3 +-containing catalyst showed considerably lower conversion. Furthermore, while the major products of the reactions over γ-alumina were vinyl chloride (C₂H₃Cl) and hydrogen chloride (HCl) at all temperatures, Cu- and Cr-doped catalysts showed significantly stronger capability for deep oxidation to CO₂.     

重金属与富里酸的竞争络合作用对其在多孔介质中运移的影响

为了研究在土壤地下水环境中运移时,多种重金属在可溶性有机质上的竞争络合作用,于阜新彰武采集草炭土并提取富里酸(FA),通过柱实验,分析了重金属与FA在多孔介质(石英砂柱)中共同运移时,FA对重金属Zn~(2+)、Cd~(2+)和Pb~(2+)运移的促进或抑制作用,以及这些重金属在FA上的竞争作用。结果表明,FA与单一组分重金属(Zn~(2+)、Pb~(2+)、Cd~(2+))在多孔介质中共同运移时,运移能力大小排序为Zn~(2+)Cd~(2+)Pb~(2+);与两组分重金属(Zn~(2+)+Pb~(2+)、Zn~(2+)+Cd~(2+)、Pb~(2+)+Cd~(2+))共同运移时,Zn~(2+)会抑制Pb~(2+)和Cd~(2+)的运移,Cd~(2+)会抑制Zn~(2+)和Pb~(2+)的运移,Pb~(2+)会促进Zn~(2+)和Cd~(2+)的运移;与三组分重金属(Zn~(2+)+Pb~(2+)+Cd~(2+))共同运移时,竞争运移的能力大小为Zn~(2+)Cd~(2+)Pb~(2+)。     

Preparation and evaluation of aminopropyl-functionalized manganese-loaded SBA-15 for copper removal from aqueous solution

A novel material, aminopropyl-functionalized manganese-loaded SBA-15 (NH₂-Mn-SBA-15), was synthesized by bonding 3-aminopropyl trimethoxysilane (APTMS) onto manganese-loaded SBA-15 (Mn-SBA-15) and used as a Cu^2 + adsorbent in aqueous solution. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction spectra (XRD), N₂ adsorption/desorption isotherms, high resolution field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the NH₂-Mn-SBA-15. The ordered mesoporous structure of SBA-15 was remained after modification. The manganese oxides were mainly loaded on the internal surface of the pore channels while the aminopropyl groups were mainly anchored on the external surface of SBA-15. The adsorption of Cu^2 + on NH₂-Mn-SBA-15 was fitted well by the Langmuir equation and the maximum adsorption capacity of NH₂-Mn-SBA-15 for Cu^2 + was over two times higher than that of Mn-SBA-15 under the same conditions. The Elovich equation gave a good fit for the adsorption process of Cu^2 + by NH₂-Mn-SBA-15 and Mn-SBA-15. Both the loaded manganese oxides and the anchored aminopropyl groups were found to contribute to the uptake of Cu^2 +. The NH₂-Mn-SBA-15 showed high selectivity for copper ions. Consecutive adsorption–desorption experiments showed that the NH₂-Mn-SBA-15 could be regenerated by acid treatment without altering its properties.     

Ca and OH release of ceramsites containing anorthite and gehlenite prepared from waste lime mud

Lime mud is a kind of solid waste in the papermaking industry, which has been a source of serious environmental pollution. Ceramsites containing anorthite and gehlenite were prepared from lime mud and fly ash through the solid state reaction method at 1050°C. The objective of this study was to explore the efficiency of Ca^2 + and OH⁻ release and assess the phosphorus and copper ion removal performance of the ceramsites via batch experiments, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that Ca^2 + and OH⁻ were released from the ceramsites due to the dissolution of anorthite, gehlenite and available lime. It is also concluded that gehlenite had stronger capacity for Ca^2 + and OH⁻ release compared with anorthite. The Ca^2 + release could be fit well by the Avrami kinetic model. Increases of porosity, dosage and temperature were associated with increases in the concentrations of Ca^2 + and OH⁻ released. Under different conditions, the ceramsites could maintain aqueous solutions in alkaline conditions (pH = 9.3–10.9) and the release of Ca^2 + was not affected. The removal rates of phosphorus and copper ions were as high as 96.88% and 96.81%, respectively. The final pH values of both phosphorus and copper ions solutions changed slightly. The reuse of lime mud in the form of ceramsites is an effective strategy.     

Effects of ionic strength and temperature on the aggregation and deposition of multi-walled carbon nanotubes

The aggregation and deposition of carbon nanotubes(CNTs) determines their transport and fate in natural waters.Therefore,the aggregation kinetics of humic-acid treated multi-walled carbon nanotubes(HA-MWCNTs) was investigated by time-resolved dynamic light scattering in NaCl and CaCl_2 electrolyte solutions.Increased ionic strength induced HA-MWCNT aggregation due to the less negative zeta potential and the reduced electrostatic repulsion.The critical coagulation concentration(CCC) values of HA-MWCNTs were 80 mmol/L in NaCl and 1.3 mmol/L in CaCl_2 electrolyte,showing that Ca~(2+) causes more serious aggregation than Na~+.The aggregation behavior of HA-MWCNTs was consistent with Derjaguin-Landau-Verwey-Overbeek theory.The deposition kinetics of HA-MWCNTs was measured by the optical absorbance at 800 ran.The critical deposition concentrations for HA-MWCNT in NaCl and CaCl_2 solutions were close to the CCC values,therefore the rate of deposition cannot be increased by changing the ionic strength in the diffusion-limited aggregation regime.The deposition process was correlated to the aggregation since larger aggregates increased gravitational deposition and decreased random Brownian diffusion.HA-MWCNTs hydrodynamic diameters were evaluated at 5,15 and 25℃.Higher temperature caused faster aggregation due to the reduced electrostatic repulsion and increased random Brownian motion and collision frequency.HA-MWCNTs aggregate faster at higher temperature in either NaCl or CaCl_2electrolyte due to the decreased electrostatic repulsion and increased random Brownian motion.Our results suggest that CNT aggregation and deposition are two correlated processes governed by the electrolyte,and CNT transport is favored at low ionic strength and low temperature.     

鸟粪石天然沸石复合材料对水中铅离子的去除

将一种含鸟粪石的氮磷回收产物(NZ-MAP)应用于水中重金属离子铅的去除.通过XRD、FTIR、SEM/EDS分析手段对NZ-MAP进行表征,并探究投加量、溶液初始pH、反应时间对去除过程的影响.结果表明NZ-MAP材料主要成分为负载有鸟粪石的天然沸石;当投加量为0. 4 g·L~(-1)时,最大吸附量为749. 74 mg·g~(-1),同时NZ-MAP对溶液中Pb~(2+)的吸附量随pH的增大呈先增加后趋于平衡的趋势,其去除机理主要为Pb_(10)(PO_4)_6(OH)_2沉淀作用,且当pH为5. 0时效果最佳.该材料对于水中铅离子的去除过程更加符合准二级动力学模型.为深入探讨共存重金属离子对NZ-MAP去除水中铅离子的影响,发现共存Ni~(2+)和Cu~(2+)对NZ-MAP吸附Pb~(2+)的影响较小,共存Zn~(2+)和Al~(3+)明显抑制了NZ-MAP对Pb~(2+)的吸附.研究显示,NZ-MAP材料可高效去除水中铅离子,可为水体中铅离子的去除提供有效的方法     

磁性竹基炭对Pb2+、Cd2+与Cu2+的吸附机理研究

采用微波辐照技术,以枯竹子为碳源制备了磁性竹基炭(BBMC),并将其用于对重金属离子Pb2+、Cd2+与Cu2+的吸附去除.同时,分析了吸附时间、pH值、离子强度及初始金属离子浓度等条件对吸附的影响,讨论了BBMC对3种金属离子的吸附特性与吸附机理.结果表明,金属离子在BBMC上的吸附符合Langmuir等温模式和准二级动力学吸附方程;吸附的机理可归结为金属阳离子与BBMC上的H+之间的离子交换作用,且吸附能力可能与金属离子半径有关,呈现出Pb2+Cd2+Cu2+的趋势,重金属离子Pb2+、Cd2+与Cu2+的最大平衡吸附量分别为16.2、14.0和9.5 mg·g-1.     

Removal of Cs from water and soil by ammonium-pillared montmorillonite/Fe3O4 composite

To remove cesium ions from water and soil, a novel adsorbent was synthesized by following a one-step co-precipitation method and using non-toxic raw materials. By combining ammonium-pillared montmorillonite (MMT) and magnetic nanoparticles (Fe₃O₄), an MMT/Fe₃O₄ composite was prepared and characterized. The adsorbent exhibited high selectivity of Cs⁺ and could be rapidly separated from the mixed solution under an external magnetic field. Above all, the adsorbent had high removal efficiency in cesium-contaminated samples (water and soil) and also showed good recycling performance, indicating that the MMT/Fe₃O₄ composite could be widely applied to the remediation of cesium-contaminated environments. It was observed that the pH, solid/liquid ratio and initial concentration affected adsorption capacity. In the presence of coexisting ions, the adsorption capacity decreased in the order of Ca^2 + > Mg^2 + > K⁺ > Na⁺, which is consistent with our theoretical prediction. The adsorption behavior of this new adsorbent could be expressed by the pseudo-second-order model and Freundlich isotherm. In addition, the adsorption mechanism of Cs⁺ was NH₄⁺ ion exchange and surface hydroxyl group coordination, with the former being more predominant.