海洋硫酸盐还原菌对Q235钢腐蚀行为的影响

采用失重法、开路电位、电化学阻抗谱(EIS)、极化曲线等方法,通过在海洋环境中浸泡不同时间对比分析有无硫酸盐还原菌(SRB)条件下Q235钢的腐蚀电化学特征,研究SRB对Q235钢的腐蚀行为的影响。结果表明,在含SRB的海水中,随着浸泡时间延长,Q235钢的腐蚀电流密度先从7.49mA·cm~(-2)增加至9.77mA·cm~(-2),然后逐渐减小至5.01mA·cm~(-2),最终增加至12.6mA·cm~(-2),且始终小于相同时间下无SRB海水中的腐蚀电流密度,表明SRB的存在抑制了Q235的腐蚀。在含SRB的海水中,Q235钢的腐蚀行为主要由Cl~-和生物膜共同影响。在SRB稳定生长阶段,腐蚀以生物膜抑制为主;在SRB指数生长阶段和衰亡阶段,生物膜抑制作用较弱,以Cl~-促进金属腐蚀为主。     

Kinetic and isotherm studies of cadmium adsorption on manganese nodule residue

The adsorption equilibrium and kinetics studies of cadmium (Cd) ions from aqueous solutions on manganese nodule residue were carried out by considering the influence of various parameters, such as contact time, solution pH and initial metal concentration in solution, temperature and adsorbent quantity. The adsorption of Cd increased with an increase in the concentrations of this metal in solution. Presence of manganese and iron content in manganese nodule residue (MNR) played a significant role in Cd(II) ions removal. The linear forms of the Langmuir and Freundlich equations were utilized for experiments with metal concentrations of 200 mg/L for Cd(II) as functions of solution pH (2.0-6.0). First-order rate equation and pseudo second-order rate equations were applied to study adsorption kinetics. Mass transfer study was also done to know the reaction rate. Thermodynamic parameters, such as standard Gibb's free energy (deltaG(o)), standard enthalpy (deltaH(o)) and standard entropy (deltaS(o)), were also evaluated by Van't Hoff equation. Thus, adsorption of Cd on this adsorbent was found to be spontaneous and exothermic thermodynamically. The adsorption capacity for Cd was found to be 19.8 mg/g of MNR. Under the optimised conditions, cadmium level was brought down from 100 mg/L to Cd less than detection limits and from 200 to 2 mg/L. Thus, the wastewater after cadmium removal could be safely disposed off on to land or sewage. Finally, the metal loaded adsorbent was subjected to desorption using different mineral acids and leaching by using toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP) tests for its further treatment or its safe disposal.     

Interaction between sulfate-reducing bacteria and aluminum alloys——Corrosion mechanisms of 5052 and Al-Zn-In-Cd aluminum alloys

Microbiologically influenced corrosion caused by sulfate-reducing bacteria(SRB) poses a serious threat to marine engineering facilities.This study focused on the interaction between the corrosion behavior of two aluminum alloys and SRB metabolic activity.SRB growth curve and sulfate variation with and with aluminum were performed to find the effect of two aluminum alloys on SRB metabolic activity.Corrosion of 5052 aluminum alloy and Al-Zn-In-Cd aluminum alloy with and without SRB were performed.The results showed that both the presence of 5052 and Al-Zn-In-Cd aluminum alloy promoted SRB metabolic activity,with the Al-Zn-In-Cd aluminum alloy having a smaller promotion effect compared with 5052 aluminum alloy.The electrochemical results suggested that the corrosion of the Al-Zn-In-Cd aluminum alloy was accelerated substantially by SRB.Moreover,SRB led to the transformation of Al-Zn-In-Cd aluminum alloy corrosion product from Al(OH)3 to Al2 S3 and NaAlO2.     

Microbial conversion of sulfur dioxide in flue gas to sulfide using bulk drug industry wastewater as an organic source by mixed cultures of sulfate reducing bacteria

Mixed cultures of sulfate reducing bacteria (SRB) were isolated from anaerobic cultures and enriched with SRB media. Studies on batch and continuous reactors for the removal of SO(2) with bulk drug industry wastewater as an organic source using isolated mixed cultures of SRB revealed that isolation and enrichment methodology adopted in the present study were apt to suppress the undesirable growth of anaerobic bacteria other than SRB. Studies on anaerobic reactors showed that process was sustainable at COD/S ratio of 2.2 and above with optimum sulfur loading rate (SLR) of 5.46kgS/(m(3)day), organic loading rate (OLR) of 12.63kg COD/(m(3)day) and at hydraulic residence time (HRT) of 8h. Free sulfide (FS) concentration in the range of 300-390mgFS/l was found to be inhibitory to mixed cultures of SRB used in the present studies.     

硫酸盐还原菌生物膜在不锈钢腐蚀过程中的作用

为了进一步了解不锈钢在硫酸盐还原菌(SRB)介质中的腐蚀过程,利用原子力显微镜(AFM)探测了海水介质中18-8SS不锈钢表面SRB生物膜的形貌特征以及生物膜下不锈钢表面状态的变化。结果表明:SRB生物膜呈"鳞片"状,并且生长时间越长,膜层越紧密;不锈钢在SRB介质中很容易发生点蚀,但SRB生物膜能为点蚀以外的完好表面提供一定的保护能力。     

The coating of cadmium compounds with nickel compounds

Micrometer-sized particles of cadmium carbonate (cores) were prepared by homogeneous precipitation from aqueous solution containing urea in the presence of cadmium sulfate. These particles were then homogeneously coated with a layer of nickel hydroxy carbonate by heating their dispersion in aqueous solution, containing nickel sulfate and urea, at 85 °C for 70 min with constant agitation. The same solution mixture produced spheroids of nickel hydroxy carbonate (coating precursors), when heated under similar conditions in the absence of the cadmium carbonate particles. The existence of the coated layer on the cores and its composition was confirmed by various physical methods. The as-prepared carbonated solids (cores, coating precursors, and coated particles) were converted into their oxide forms by calcination at 700 °C. The cores became porous, whereas the coating precursors and coating layer disintegrated into smaller particles during the calcination process.     

THE EFFECT OF TARTRATE, A WEAK COMPLEXING AGENT, ON THE REMOVAL OF HEAVY METALS BY SULFIDE AND HYDROXIDE PRECIPITATION

Industrial vastevaters generated in the electroplating and metal finishing industries typically contain toxic heavy metals. Depending on their origin, these wastewaters may also contain chelating agents, such as EDTA, NTA, citrate, tartrate, and gluconic acid. Although the major effect of complexation is an increase in the solubility of complexed metal ions, significant changes in the precipitation kinetics and particle size distribution may also contribute to the observed precipitation behavior.

This paper addresses the effect of a weak complexing agent, tartrate, on the removal of zinc and cadmium using both hydroxide and sulfide treatment. Results are presented on the removal of heavy metals from synthetic plating wastewaters. Poor zinc removals were observed in the presence of tartrate, particularly when larger filter pore sizes were employed. The results suggest that tartrate severely hinders both zinc hydroxide and zinc sulfide precipitation, resulting in the formation of very fine precipitates; this was confirmed when no zinc removal occurred even with a settling time of 30 min. For removal of cadmium, virtually no change in residual cadmium concentration was observed in the presence of tartrate (compared to the case of no complexing agents present) due to the formation of low-stability complexes.     

THE EFFECT OF COMPLEXING AGENTS ON THE PRECIPITATION AND REMOVAL OF COPPER AND NICKEL FROM SOLUTION

This paper addresses the effect of the complexing agents citrate, tartrate, ammonia, phosphate, and EDTA on the removal of copper and nickel from solution using both hydroxide and sulfide precipitation. Both batch and continuous metal sulfide precipitation experiments were performed. Results are presented for the removal of heavy metals and the resulting particle size distributions. The presence of weak complexing agents (citrate, tartrate, ammonia, and phosphate) had a minimal effect on the removal of copper and nickel, while the presence of a strong complexing agent (EDTA) resulted in the residual metal concentration being 1-2 orders of magnitude greater than the case with no complexing agents present. In an open system, the residual nickel concentration increased with increasing reaction time, due to the oxidation of nickel sulfide co nickel sulfate. For copper sulfide precipitation, the presence of complexing agents reduced the precipitate growth rate, nuclei density, and nucleation rate, resulting in a decrease of the dominant particle size (as compared to copper sulfide precipitation with no complexing agents present). The value of the kinetic order, i, decreased, while the kinetic rate constant, kN, increased in the presence of EDTA.     

Inhibition of sulfate reduction by iron, cadmium and sulfide in granular sludge

This study investigated the inhibition effect of iron, cadmium and sulfide on the substrate utilization rate of sulfate reducing granular sludge. A series of batch experiments in a UASB reactor were conducted with different concentrations of iron (Fe²⁺, 4.0–8.5 mM), cadmium (Cd²⁺, 0.53–3.0 mM) and sulfide (4.2–10.6 mM), the reactor was fed with ethanol at 1 g chemical oxygen demand (COD)/L and sulfate to yield a COD/SO₄²⁻ (g/g) ratio of 0.5. The addition of iron, up to a concentration of 8.1 mM, had a positive effect on the substrate utilization rate which increased 40% compared to the rate obtained without metal addition (0.25 g COD/g VSS-d). Nonetheless, iron concentration of 8.5 mM inhibited the specific substrate utilization rate by 57% compared to the substrate utilization rate obtained in the batch amended with 4.0 mM Fe²⁺ (0.44 g COD/g VSS-d). Cadmium had a negative effect on the specific substrate utilization rate at the concentrations tested; at 3.0 mM Cd²⁺ the substrate utilization rate was inhibited by 44% compared with the substrate utilization rate without metal addition. Cadmium precipitation with sulfide did not decrease the inhibition of cadmium on sulfate reduction. These results could have important practical implications mainly when considering the application of the sulfate reducing process to treat effluents with high concentrations of sulfate and dissolved metals such as iron and cadmium.     

海洋硫酸盐还原菌对X100钢腐蚀行为的影响

通过测定海水溶液中硫酸盐还原菌(SRB)生长曲线、溶液状态参数、自腐蚀电位、电化学阻抗谱和极化曲线的变化规律,研究了SRB的存在对X100钢在该体系中的腐蚀行为的影响。结果表明:SRB在海水培养基中的一个生长周期可分为快速生长阶段、稳定阶段和衰亡阶段。溶液S2-浓度和氧化还原电位与SRB数目密切相关,X100钢的自腐蚀电位随时间增加呈现先负移、然后正移、最后负移的变化规律;EIS结果表明,在接菌海水中,X100钢的腐蚀速率随着浸泡时间的增加呈现先增大、后减小、再增大的变化趋势;与灭菌海水中的腐蚀相比,X100钢在接菌海水中的腐蚀电流密度降低,腐蚀减弱,其原因是SRB生物膜的存在阻碍了海水与试样表面的直接接触,从而抑制了金属的腐蚀。     

Toxic effects of dissolved heavy metals on Desulfovibrio vulgaris and Desulfovibrio sp. strains

Biological treatment of metal-containing wastewaters with sulphate-reducing bacteria (SRB) is an attractive technique for the bioremediation of this kind of medium. In order to design a suitable engineering process to address this environmental problem, it is crucial to understand the inhibitory effect of dissolved heavy metals on these bacteria. Batch studies were carried out to evaluate the toxic effects of several heavy metal ions [Cr(III), Cu(II), Mn(II), Ni(II) and Zn(II)] on two cultures of SRB (Desulfovibrio vulgaris and Desulfovibrio sp.). The experimental data indicate that SRB show different responses to each metal. At the highest metal concentration tolerated for each metal, the precipitation levels for D. vulgaris were as follows: 24.7%-15 ppm Cr(III), 45%-4 ppm Cu(II), 60%-10 ppm Mn(II), 96%-8.5 ppm Ni(II) and 9%-20 ppm Zn(II). The corresponding values for Desulfovibrio sp. were: 25.5%-15 ppm Cr(III), 71%-4 ppm Cu(II), 66.2%-10 ppm Mn(II), 96.1%-8.5 ppm Ni(II) and 93%-20 ppm Zn(II). Results obtained in batch studies will be taken into account for the subsequent design of a sulphate-reducing bioreactor to reduce levels of heavy metals present in different types of contaminated media.     

海滨盐碱土壤中硫酸盐还原菌对X100管线钢腐蚀行为的影响

为了进一步明确X100管线钢在含硫酸盐还原菌(SRB)海滨盐碱土壤中的耐蚀性,采用表面分析技术、电化学技术和失重法,研究了SRB对X100管线钢腐蚀过程与行为的影响。结果表明:X100管线钢在有无SRB海滨盐碱土壤中的腐蚀均属于中度腐蚀,无SRB时腐蚀产物主要为Fe_2O_3,Fe_3O_4和γ-Fe O(OH),有SRB时腐蚀产物主要为Fe_2O_3,Fe_3O_4,α-Fe O(OH)和Fe7S8;SRB代谢形成的活性生物膜影响了X100管线钢的腐蚀行为,随着腐蚀时间的增加,SRB可在X100管线钢表面形成由微生物膜与腐蚀产物结合的膜,其更加致密,对腐蚀传质具有物理阻碍作用,可以减缓X100管线钢的腐蚀;无SRB菌时X100管线钢表面的腐蚀产物疏松多孔并分布有裂纹,且对基体的保护作用差,其腐蚀速率大于有SRB时的值;SRB的代谢活动抑制了X100管线钢的腐蚀。     

Isotherm studies of lead(II), manganese(II), and cadmium(II) adsorption by Nigerian bentonite clay in single and multimetal solutions

This study was aimed at evaluating the isotherm of lead(II), manganese(II), and cadmium(II) adsorption in single and multimetal solutions using Nigerian bentonite. The natural and calcined clays were characterized for specific surface area, surface morphology, elemental composition, and cation exchange capacity (CEC). The adsorption data were analyzed and interpreted using isotherm models. The natural bentonite exhibits a specific surface area of 23.5?m²/g and a CEC value of 47.7 mEq/100?g and displays a higher adsorption capacity of all heavy metals in both single and multimetal solutions than the calcined bentonite. The removal of lead(II) by natural bentonite in single-component system is 0.0448?mmol/g. The order of selectivity is lead(II)?>?cadmium(II)?>?manganese(II). Result also shows that both clays demonstrate a preferable adsorption toward lead(II). Lead(II) adsorption is less affected by the presence of counter cations in multimetal solution. The adsorption of heavy metals onto Dijah-Monkin bentonite is site selective and site specific, and the adsorption data are well presented by the Langmuir model. The CEC could be the primary mechanism for the uptake of heavy metals, and the removal capacity was shown to depend on the ionic radius of metal ions.     

海泥中硫酸盐还原菌对1Cr13不锈钢腐蚀的影响

利用交流阻抗测试技术，扫描电镜及表面能谱、失重法、微生物分析等方法，在室内模拟条件下研究了海泥中硫酸盐还原菌对1Cr13不锈钢腐蚀的影响，及在含和不含硫酸盐还原菌的海泥构成的宏电池腐蚀中1Cr13不锈钢的腐蚀行为。试验结果表明，在有菌泥中1Cr13不锈钢的自然腐蚀速度均大于在灭菌泥中，两相差5．1倍。说明海泥中硫酸盐还原菌增大了1Cr13不锈钢的腐蚀速率。在有菌和灭菌海泥构成宏电池时，有菌海泥中1Cr13不锈钢作为阳极，腐蚀速率比自然腐蚀状态下有所增大，加速率为14．6％。而在灭菌海泥中1Cr13不锈钢作为阴极，腐蚀速率比自然腐蚀状态下有所减小。     

Anaerobic biotransformation of fluorene and phenanthrene by sulfate-reducing bacteria and identification of biotransformation pathway

In the present study, anaerobic biotransformation of fluorene and phenanthrene by sulfate-reducing bacteria (SRB) was investigated and biotransformation pathways were proposed. SRB was enriched from anaerobic swine wastewater sludge and its abundance was determined by the fluorescence in situ hybridization (FISH) technique. Batch anaerobic biotransformation studies were conducted with fluorene (5 mg L(-1)), phenanthrene (5 mg L(-1)) and a mixture of the two (10 mg L(-1)). After 21d of incubation, 88% of fluorene and 65% of phenanthrene were biotransformed by SRB. In contrast to previous studies, a decrease in biotransformation efficiency was observed in the presence of both fluorene and phenanthrene. Throughout the study, sulfate reduction was coupled with biotransformation of fluorene and phenanthrene. However, no increase in bacterial cell density was observed in the presence of an inhibitor, i.e. molybdate. Identification of metabolites by gas chromatography-mass spectrometry (GC-MS) revealed that fluorene and phenanthrene were biotransformed through a sequence of hydration and hydrolysis reactions followed by decarboxylation with the formation of p-cresol (only in the phenanthrene system) and phenol. The metabolites identified suggest novel biotransformation pathways of fluorene and phenenthrene.     

Effect of organic silicon quaternary ammonium salts on mitigating corrosion of reinforced steel induced by SRB in mild alkaline simulated concrete pore solution

The corrosion damage of 20 SiMn steel by sulphate-reducing bacteria(SRB)and the mitigation effect of organic silicon quaternary ammonium salt(OSA)were studied in sterilized mild alkaline simulated concrete pore solution(STR)with different additions of SRB and OSA at pH 9.35 for 28 days.Uniform corrosion occurs in STR medium while slight localized corrosion is observed in STR+OSA medium,and localized pitting corrosion occurs in STR+SRB and STR+SRB+OSA media.The largest pit depth reduces from 36.70μm in STR+SRB medium to 3.31μm in STR+SRB+OSA medium due to the mitigation effect of OSA.The corrosion rate reflected by weight loss and electrochemical impedance spectroscopy(EIS)results presents the order of STR相似文献   

Adsorption removal of cadmium and copper from aqueous solution by areca: a food waste

Areca waste (AW) has been investigated as metal biosorbent for cadmium and copper from aqueous solution for its availability as food waste and also for its cellulosic matrix rich of potential metal binding active sites. The effect of various parameters on adsorption process such as contact time, solution pH, amount of AW and initial concentration of metal ions was studied at room temperature to optimize the conditions for maximum adsorption. Maximum metal sorption was found to occur at pH 5.6. Adsorption process revealed that the initial uptake was rapid and equilibrium was established about in 1h for cadmium and copper. The equilibrium sorption data for single metal systems at pH 5.6 were described by the Langmuir, Freundlich and D-R isotherm models. The adsorption isotherm studies clearly indicated that the adsorptive behaviour of metal ions on AW not only the Langmuir assumptions but also the Freundlich and the D-R assumptions. The highest value of Langmuir maximum uptake, (b), was found for cadmium (1.12 mg/g) and copper (2.84 mg/g). Similar Freundlich empirical constants, K, were obtained for cadmium (1.086) and copper (1.119). Ion-exchange and surface adsorption might be involved in the adsorption process of cadmium and copper. Desorption studies revealed that cadmium and copper can be easily removed from AW by altering the pH values of the solution using HNO(3), indicating that AW are a promising adsorbent for wastewater treatment.     

脱氮硫杆菌对碳钢微生物腐蚀的影响

将实验室分离纯化所得的脱氮硫杆菌(简称T．denitrificans)用于硫酸盐还原菌(简称SRB)引起的微生物腐蚀的防治。采用静态挂片、交流阻抗法(EIS)等方法，研究了Q235钢在接种SRB以及SRB和T．denitrificans共存培养基介质中的腐蚀行为；并借助扫描隧道显微镜、电子探针等表面分析手段，研究了碳钢腐蚀过程中生物膜的形貌及致密程度的变化以及生物膜中细菌的新陈代谢产物。研究结果表明：SRB的存在加速了Q235钢的腐蚀，若该体系中有T．denitrificans共存，可明显降低碳钢微生物腐蚀的程度，且共生生物膜较SRB单独存在时的生物膜更为致密，该生物膜中硫化物含量远比SRB生物膜中的含量低。     

The mechanism of the low-temperature hot corrosion of pure iron and manganese at 600–800°C

The corrosion of pure iron and manganese in simulated combustion gases at 600–800°C in the presence of sodium sulfate deposits is faster than the same reaction without salt deposits. This effect is due to the formation of a liquid solution between sodium sulfate and the sulfates of the corroded metals. The nature of these liquid solutions is examined together with the possible mechanisms for the transport of matter through the liquid and the dissolution-reprecipitation of solid metal compounds in the liquid salt. Finally, the reasons for the formation of sulfides in mixture with oxides in the inner solid region of the scale and the effects produced by the presence of sulfides on the overall reaction rate are considered.     

MOBILIZATION AND RETENTION OF MERCURY AND LEAD FROM PARTICULATES CO-DISPOSED WITH MUNICIPAL SOLID WASTES

Metal sludges containing mercury and lead were codisposed among other metals with municipal solid waste in test columns (lysimeters) and leachate generation initiated by addition of water. Leachate was collected from these columns and the levels of these metals measured to provide an index of metal mobilities and mechanisms of control of those mobilities. In addition, other parameters likely to be pertinent to the mobilities of mercury and lead such as pH, ORP and inorganic anion concentrations were monitored. While efforts were also made to monitor sulfide no sulfide was detected in the leachates. The behavior of lead in these columns was consistent with precipitation by the abundant sulfate present in the leachates modified to some extent by complexation with both sulfate and chloride. The behavior of mercury was fully consistent with reduction of added mercuric to the neutral metal. While its presence could not be excluded by the data, no clear evidence of the presence of sulfide was obtained.