Search

A reliable method for the determination of dissolved Cu2+ and Pb2+ species in water via a diffusive gradient in thin films (DGT) device using water-soluble carbon nanodots (CD) as the binding agent was developed (CD-DGT). The uptake of dissolved Cu2+ and Pb2+ species by CD-DGT increased linearly with a deployment time of over 120 h, while the uptake of Ca2+, Mg2+, Cd2+, Zn2+, Ni2+, and Co2+ by CD-DGT has no significant linear accumulation during the same deployment time. The concentrations of the dissolved Cu2+ and Pb2+ species measured using CD-DGT are in good agreement with the element concentrations spiked directly in a tested synthesis solution. The performance of CD-DGT for the determination of dissolved Cu2+ and Pb2+ species is found to be independent of ionic strength in the range of 0.001–0.05 mol L−1 and in the pH range from 5 to 8. The presence of fulvic acid and tannic acid has no significant influence on the uptake of dissolved Cu2+ and Pb2+ species by CD-DGT under the tested conditions. In different water samples, good agreement was observed between the dissolved Cu2+ and Pb2+ concentrations measured by CD-DGT, and diffusive equilibration in the thin film devices was found. Based on the results obtained, CD-DGT enables the selective and quantitative determination of dissolved Cu2+ and Pb2+ species in water. [ABSTRACT FROM AUTHOR]

Abstract Membrane pore wetting is the main problem hindering long term stability of permeate flux quality in membrane distillation (MD) applications. A superhydrophobic membrane with micro and nanostructured surface features can offer a unique solution to resolve this issue. Thus, a modified electrospun membrane was fabricated using a combination of electrospinning and electrospraying. The membrane surface hydrophobicity was enhanced by constructing a beaded structure from spraying a mixture of non-fluorinated alumina (Al 2 O 3) nanoparticles (NPs) mixed with low concentration of PVDF polymer on an electrospun base membrane made from PVDF. The results revealed that a rough surface with a hierarchical structure can be constructed, which could not only enhance the membrane hydrophobicity, but also further enhance the permeate efficiency by improving parameters such as flux and rejection. Additionally, the membrane hydrophobicity could be further tuned by controlling the bead spinning volume. Our study shows that the modified membrane with 7.8 μm beads layer thickness has boosted the liquid entry pressure (LEP) by 61% from 15.5 psi and the water contact angle to 154°. The performance of modified membranes with different spraying volume (1–5 ml) along with the neat electrospun and commercial membranes were examined in an air gap membrane distillation (AGMD) application for 5 h using a 2.5 wt% of synthetic heavy metal solution as a wastewater model. Then, the optimized superhydrophobic membrane with 2 ml spinning volume (ES15–2) was further tested in comparison with the commercial membrane during long-term operations (30 h) using 3.5 wt% of mixed heavy metals. The flux was 18.67 LMH (l m−2 h−1) for modified membrane (ES15–2) compare with 12.62 LMH for commercial PVDF membrane during 30 h of long-term operation with feed and coolant temperature at 60 °C, 20 °C, respectively. The present superhydrophobic membrane fabricated by a combined electrospinning/electrospray method shows high potential for MD applications. Graphical abstract Unlabelled Image Highlights • Superhydrophobic electrospun membrane fabricated • Combination electrospray with electrospinning technique • Effect of bead density and spray layer thickness on morphology and wetting properties • High liquid entry pressure, water contact angle and low sliding angle achieved [ABSTRACT FROM AUTHOR]

Nanoscale zero-valent iron (nZVI), an environmentally benign material, has been used to remove heavy metals and metalloids from the aqueous phase because of its high reactivity and abundant reactive sites. To improve the stability of nZVI, nanoscale zero-valent iron supported by amino-modified biochar (ZVIA-BC) was prepared and characterized. Its ability to remove heavy metals and metalloid was investigated. Fourier transform infrared spectroscopy analyses showed that the amino group was chemically bound to the functional groups of biochar. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction revealed that zero-valent iron was loaded on the biochar surface. High-resolution transmission electron microscope images showed that the particle size of iron was ~50 nm and the particles consisted of roughly spherical cores covered with a shell that was uniformly 2- to 3-nm thick. Furthermore, measuring the zeta potentials at various pH values indicated that the iso-electric points occurred within the pH range of 7.50 to 7.56. Additionally, heavy metals and metalloids, including Cd(II), Ni(II), Cu(II), Cr(VI) and As(V) adsorption isotherms, on ZVIA-BC were significantly nonlinear, and ZVIA-BC exhibited a superior ability to remove these heavy metals and metalloids, especially for Cr(VI) and As(V). Characterization with high-resolution XPS revealed that reduction of heavy metals and metalloids occurred on the surface of ZVIA-BC. The main mechanisms for removal were reduction, complexation, co-precipitation, and electrostatic interaction. [ABSTRACT FROM AUTHOR]

This study performed in Sapanca Lake catchment area, used as a drinking water resource. Two highways located at northern and southern shores, and a railway at its south are significant sources of pollution. As a possible solution for protecting water quality a pocket wetland constructed and operated. Performances statistically interpreted by Spearman's Correlation test and univariate analysis of variance on collected data. The mean removal efficiencies obtaited were 52% (TSS), 4% (Nitrate), 26% (TN), −5% (TOC), 63% (TP), 4.5% (Chloride), 3% (Sulfate), 33% (Cr), 39% (Co), −19.5% (Ni), 7% (Cu), 55% (Zn), 36% (As), 38% (Cd) and 18% (Pb). TSS removal was in positive significant medium correlation with Co, Cu, Zn, and Pb removal respectively (p < 0.05). Other statistically significant positive high correlations calculated between removal efficiency of Nitrate–TN, Chloride–Sulfate, Cr–Co–Cu–As–Cd. According to ANOVA and Kruskal-Wallis test results, removal efficiencies of TSS and TOC partially affected by different temperature (p < 0.1 for TSS and p < 0.05 for TOC) and pH ranges (p < 0.1 for both removal efficiencies), TP removal efficiency significantly affected by different pH ranges (p < 0.001), and Chloride and Sulfate removal efficiencies were significantly (p < 0.001) affected by different temperature ranges. Regardless of geographical location and climatic factors, pocket wetland systems can be relied upon for minimizing heavy metals such as Cr, Co, Zn, As, Cd and Pb and critical pollutants such as TP and TSS caused by highway runoff. [ABSTRACT FROM AUTHOR]

Paddy field soil contaminated by cadmium may produce cadmium-contained corns causing Itai-itai disease, and in situ washing of soil with the organic acid is a good technical choice due to its convenience and cost-effectiveness. While the bottleneck of this technique is how to recycle the huge volume of washing effluent in an efficient and economical way. Biosorption of cadmium on the garlic peel was attempted in present study and it was found quite satisfactorily effective to remove all cadmium from the real soil leaching effluent after three-time sequential adsorption. The systematical investigation on the effect of various parameters on the adsorption of cadmium on garlic peel in the existence of tartaric ligand was performed and it was found that tartrate could change Cd2+ into Cd(tar)0 species whose electrical charge state would restrain its approach to the adsorbent particles. The porous microstructure in the transversal surface of garlic peel and the abundant groups of −COOH are the main factors affecting the adsorption capability. A demonstrative flowsheet of soil remediation by chemical washing coupled with biosorption was proposed correspondingly, in which the cadmium could be recovered from the soil washing effluent, and the recovered effluent was reused for next soil washing, and recovered garlic peel was reused for cadmium adsorption from the effluents again, showing a great prospect in the remediation of paddy field soil contaminated by cadmium.Garlic peel was used to remove the cadmium from the soil washing effluent [ABSTRACT FROM AUTHOR]

In this work, a novel rotational microfluidic paper-based device was developed to improve the accuracy and performance of the multiplexed colorimetric detection by effectively avoiding the diffusion of colorimetric reagent on the detection zone. The integrated paper-based rotational valves were used to control the connection or disconnection between detection zones and fluid channels. Based on the manipulation of the rotational valves, this rotational paper-based device could prevent the random diffusion of colorimetric reagent and reduce the error of quantitative analysis considerably. The multiplexed colorimetric detection of heavy metals Ni(II), Cu(II) and Cr(VI) were implemented on the rotational device and the detection limits could be found to be 4.8, 1.6, and 0.18 mg/L, respectively. The developed rotational device showed the great advantage in improving the detection accuracy and was expected to be a low-cost, portable analytical platform for the on-site detection. [ABSTRACT FROM AUTHOR]

Nanostructured materials have been successfully applied to efficiently remove toxic and carcinogenic contaminants such as heavy metals from wastewater. In this work, polyacrylonitrile (PAN) was selected as base polymer for electrospinning process to obtain easily modifiable and versatile nanofibers able to remove selectively heavy metal ions from contaminated effluents. Chemical functionalities were grafted in a stable and homogeneous way by a two steps grafting process which involves hydrolysis and chemical modification with ethylenediamine (EDA), ethyleneglycol (EG) or diethylenetriamine (DTA) resulting in three ion-selective nanofibrous materials. Their adsorption behaviour was tested against Cu(II), Pb(II) and Zn(II) reaching extremely high adsorption capacities of 6.1 mmol/g, 8.8 mmol/g and 7.2 mmol/g, respectively. [ABSTRACT FROM AUTHOR]

In the present study, theoretical and experimental investigations were carried out to examine the effect of changing the operating parameters of an air gap membrane distillation (AGMD) system on the performance of electrospun and commercial membranes. These parameters include feed, cooling water temperature and feed flow rate. Analytical models were used, with the aid of MATLAB, to predict the permeate flux of AGMD based on heat and mass transfer. Heat transfer was used to predict the temperature on the membrane surface on the feed side and the thin film layer in the cooling plate on the air gap side, which was used later to calculate the vapour pressure and the permeate flux. The molecular diffusion model corresponded well with the experimental measurements in terms of predicting the permeate flux by varying the feed temperature, while it was poor in term of coolant temperature and feed flow rate. The results also illustrate that high rejection rates of around 99% of heavy metals can be achieved by using superhydrophobic electrospun membranes. The electrospun membrane flux increased with increasing feed tank temperature and flow rate while it was reduced with an increase of cooling line temperature. [ABSTRACT FROM AUTHOR]

The aim of this paper was to conduct pilot-scale column tests on an alternative treatment filter designed for the treatment of highway stormwater in cold climates. The study evaluated adsorption performance of the filter with regard to the four most commonly found metals (Cu, Ni, Pb, and Zn) in highway stormwater. An alternative method was used to estimate the operational life of the filter from the adsorption test data without a breakthrough under high hydraulic loads. The potential environmental impact of the filter was assessed by comparing desorption test data with four different environmental quality standards. The proposed filter achieved high adsorption (over 90%) of the target metals. The comparisons of desorption and leaching data with the environmental standards indicated that iron-oxide/bottom ash was non-hazardous, reusable and without serious environmental risks. The operational life and filter dimensions were highly dependent on rainfall depth, which indicated that the filter design would have to be adapted to suit the climate. To fully appreciate the performance and environmental aspects, the filter unit should be tested in the field and the testing should explicitly include ecotoxicological and life cycle impacts. [ABSTRACT FROM PUBLISHER]

Urban road stormwater is an alternative water resource to mitigate water shortage issues in the worldwide. Heavy metals deposited (build-up) on urban road surface can enter road stormwater runoff, undermining stormwater reuse safety. As heavy metal build-up loads perform high variabilities in terms of spatial distribution and is strongly influenced by surrounding land uses, it is essential to develop an approach to identify hot-spots where stormwater runoff could include high heavy metal concentrations and hence cannot be reused if it is not properly treated. This study developed a robust modelling approach to estimating heavy metal build-up loads on urban roads using land use fractions (representing percentages of land uses within a given area) by an artificial neural network (ANN) model technique. Based on the modelling results, a series of heavy metal load spatial distribution maps and a comprehensive ecological risk map were generated. These maps provided a visualization platform to identify priority areas where the stormwater can be safely reused. Additionally, these maps can be utilized as an urban land use planning tool in the context of effective stormwater reuse strategy implementation. [ABSTRACT FROM AUTHOR]

Heavy metals from urban stormwater runoff are important sources of surface water pollutants. Sand, zeolite, sandy loam, and quartz-sand were separately mixed with lignin to form four bioretention media mixes for experimental study using synthetic stormwater runoff. The average removal efficiencies of four heavy metals (Cu, Zn, Cd, and Pb) by the four media mixes were all better than 97% at the optimum pH of 6.05 (ranging from 6 to 8) and the seven-day rainfall-event interval. The influence of the influent concentration and the rainfall-event interval on the removal efficiency of heavy metals by the four media mixes was not significant, but the variation of the removal efficiencies at the four-day rainfall-event interval was large. Under acidic conditions, there was a certain heavy metal dissolution in the four reactors, but the effect on the removal efficiency was minor. Heavy metals were present in the media mainly in the form of the residual fraction (>50%). The accumulation of Cu, Zn, and Cd in the surface planting-soil layer (same humus and sandy-loam mixture for all reactors) was significantly larger than the accumulation at deeper depths but not for Pb. Overall, the heavy metal removal efficiencies by the four media mixes were not significantly different, and the choice of the planting-soil layer can become the control factor of heavy metal removal. [ABSTRACT FROM AUTHOR]

A simple, fast and green method for chiral recognition of S- and R-naproxen has been introduced. The method was based on quenching of the fluorescence intensity of bovine serum albumin–stabilized gold nanoclusters in the presence of naproxen enantiomers. The quenching intensity in the presence of S-naproxen was higher than R-naproxen when phosphate buffer solution at pH 7.0 was used. The chiral recognition occurred due to steric effect between bovine serum albumin conformation and naproxen enantiomers. Two linear determination range were established as 7.4 × 10 −7 –9.1 × 10 −6 and 9.1 × 10 −6 –3.1 × 10 −5 mol L −1 for both enantiomers and detection limits of 7.4 × 10 −8 mol L − 1 and 9.5 × 10 −8 mol L −1 were obtained for S- and R-naproxen, respectively. The developed method showed good repeatability and reproducibility for the analysis of a synthetic sample. To make the procedure applicable to biological samples, the removal of heavy metals from the sample is suggested before any analytical attempt. [ABSTRACT FROM AUTHOR]

In this study, we developed a cost effective method of using thiol functionalized γ-aluminum oxide hydroxide (γ-AlOOH) filters for removing three key heavy metals from water: mercury, lead, and cadmium under non-concomitant conditions. Compared to non-thiol treated γ-AlOOH filters, the introduction of thiol functional groups greatly improved the heavy metal removal efficiency under both static and dynamic filtration conditions. The adsorption kinetics of thiol functionalized γ-AlOOH were investigated using the Lagergren first order and pseudo-second order kinetics models; whereas the isothermal adsorption behavior of these membranes was revealed through the Langmuir and Freundlich models. Heavy metal concentration was quantified by Inductively Coupled Plasma-Mass Spectroscopy, and the thiol level on γ-AlOOH surface was measured by a colorimetric assay using Ellman's reagent. X-ray photoelectron spectroscopy was used to further address the surface sulfur state on the membranes after heavy metal exposure. Mechanisms for heavy metal adsorption were also discussed. [ABSTRACT FROM AUTHOR]

To remove heavy metal contaminations from road runoff prior to discharge into surface water or groundwater, highly porous sorptive filter materials are used. One effective material is a technical product based on granular ferric hydroxide. To specify the removal mechanisms, lab-scale column experiments were performed preloading the material with Cd, Cu, Ni, Pb, and Zn. To identify removal mechanisms and the distribution of heavy metals in the material, investigations with scanning electron microscope (SEM)/energy-dispersive X-ray spectroscopy (EDX) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were performed. With SEM/EDX, only Pb was detectable; all other heavy metals were not represented on the surface of the particles. To determine the intrusion of the metals, LA-ICP-MS was used. Thereby, the high porosity necessitated a special data evaluation that enabled the determination of the heavy metal removal and the leaching of other elements from the filter material as a function of depth. The measured depth profiles varied for each element and correlated with the metal mobility. [ABSTRACT FROM AUTHOR]

A novel marine fungus was isolated and classified as Aspergillus flavus strain EGY11. The heat-inactivated form of isolated Aspergillus flavus was investigated and evaluated as a new eco-friendly and highly efficient biosorbent for removal of toxic heavy metals such as Cd(II), Hg(II), and Pb(II) from aqueous solutions. The SEM morphological studies of biosorbent-loaded metal ions confirmed their direct binding on the surface of heat-inactivated Aspergillus flavus. The metal biosorption capacity values were determined and optimized by the batch technique in the presence of various experimental controlling factors such as pH, contact time, biosorbent dosage, initial metal ion concentration, and coexisting species. The maximum metal capacity values of Cd(II), Hg(II), and Pb(II) were cauterized as 1550 (pH 7.0), 950 (pH 7.0), and 1000 μmol g (pH 6.0), respectively. The equilibrium time for removal of metal ions was identified as 40 min. The maximum sorption capacity values (1200.0-4000.0 μmol g) were established by 5.0 mg as the optimum mass of biosorbent. The collected biosorption data obtained from the equilibrium studies using the initial metal ion concentration were described by the Langmuir, Freundlich, Brunauer-Emmett-Teller (BET), and Dubinin-Radushkevich isotherm (D-R) isotherm models. The potential implementation of heat-inactivated Aspergillus flavus biosorbent for heavy metal removal from different water samples was successfully accomplished using multistage microcolumn technique. The results refer to excellent percentage recovery values in the ranges 92.7-99.0, 91.3-95.6, and 95.3-98.2% for the biosorptive removal of Cd(II), Hg(II), and Pb(II), respectively, from the examined environmental samples. [ABSTRACT FROM AUTHOR]

Neat cellulose acetate (CA) and CA/polysulfone (PSf) blend ultrafiltration membranes in presence of polyvinylpyrrolidone as a pore former were prepared via phase inversion technique. The prepared membranes were characterized by Fourier transform infrared, scanning electron microscopy, mechanical strength, water content, porosity, permeate flux and heavy metals (Pb2+, Cd2+, Zn2+ and Ni2+) rejection to comprehend the impact of polymer blend composition and additive on the properties of the modified membranes. The water flux expanded by increasing of PSf content in the polymer composition. CA/PSf (60/40) had the highest flux among prepared membranes. Prepared blend membranes were able to remove heavy metals from water in following order: Pb2+ > Cd2+ > Zn2+ > Ni2+. CA/PSf (80/20) blend membrane had great performance among prepared membranes due to the high heavy metals removal and permeate flux [ABSTRACT FROM AUTHOR]

Mg(OH) 2 dissolves slowly and can provide a long-term source of alkalinity, thus a promising alternative reagent for the in situ remediation of heavy metal polluted groundwater. However, the application of Mg(OH) 2 on in situ reactive zone (IRZ) for heavy metal polluted groundwater has never been investigated. In this study, the behaviors of heavy metals in a Mg(OH) 2 IRZ were monitored for 45 d. The heavy metals show a sequential precipitation by modified Mg(OH) 2 due to the difference of K sp . Column tests were conducted to investigate the temporal and spatial distribution of heavy metals in Mg(OH) 2 IRZ and evaluate the stabilization effect for multi-heavy metal polluted groundwater. Experimental results indicate that there exist interactions between different heavy metals, and their zoning distribution is attributed either to the competitive adsorption onto porous media (control column) or to the sequential precipitation of heavy metal ions (IRZ column). In contrast with the control column, heavy metal contaminated area in Mg(OH) 2 IRZ significantly shrinks. According to the chemical speciation analysis, when water containing Pb(II), Cd(II) and Cr(III) flows through Mg(OH) 2 IRZ, exchangeable fraction of total concentration significantly reduce and the proportion of carbonate and Fe/Mn oxides fraction increase, indicating the decrease of their mobility and toxicity. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the removal ability of cadmium(II) and cobalt(II) ions from aqueous solution by raw and chemicly treated carob shells as an ecofriendly and sustainable biosorbents. The biosorbents were characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis (CHNOS), scanning electron microscopy (SEM), Boehm titration and the point of zero charge (pH PZC ). Biosorption experiments were carried out as function of solution pH, biosorbents dosage, contact time, initial metal ions concentration and temperature. The effect of some major inorganic ions including Na + , K + , Ca 2+ , Mg 2+ and Al 3+ on the biosorption efficiency was also investigated. From this studies it can be concluded that chemical pretreatment of the raw carob shells with NaOH strongly enhances its biosorption potential for the selected metals. Experimental results show that maximum biosorption capacity occurred at neutral pH medium. Kinetic data were best fitted with pseudo-first-order kinetic model instead of pseudo-second-order. Biosorption isotherms were best correlated with Langmuir model than with Freundlich model. The temperature doesn’t have much influence on the biosorption yield. Based on this preliminary study, full factorial experimental design with two levels (2 4 ) was used for the optimisation of the process. Four independent variables, including solution pH, biosorbents dosage, initial metal concentration and treating agent were investigated. Thus, the optimal conditions for high biosorption of cadmium(II) and cobalt(II) were achieved at pH = 6, biosorbent dosage of 1 g/L, initial metal concentration of 50 mg/L for NaOH treated carob shells. [ABSTRACT FROM AUTHOR]

Heavy metal pollution is a serious problem for Lentinula edodes; however, the treatment of contaminated L. edodes has seldom been studied. This study investigated the removal of cadmium (Cd) from contaminated L. edodes and its lentinan by complexation and coagulation. Some influencing factors, such as pH, medical dosage, and preoxidation were examined. Cd complexation from contaminated L. edodes was shown to be more efficient under acidic conditions ( pH 5.0), with a clearance rate of 80.47% in 25 mmol/L EDTA and 78.45% in 25 mmol/L sodium citrate. The Cd content in the lentinan of the contaminated L. edodes was markedly lower than that in the powdered mushroom (2.77 mg/kg vs. 19.49 mg/kg) and was easier to remove. The maximum Cd clearance rate (96.3%) for lentinan was obtained using an optimized process that involved preoxidation with 0.5 mg/L KMnO4, complexing with 25 mmol/L EDTA and 25 mmol/L sodium citrate, and coagulation with 50 mg/L activated carbon ( AC) at pH 10.0. [ABSTRACT FROM AUTHOR]

In this paper, electrical wire explosion (EWE) was used as a simple, clean, in situ method to synthesise nano zero-valent iron (nZVI) particles in liquid mediums. The structural and physical properties of the synthesised nZVI particles were characterised by x-ray diffraction, Brunauer-Emmett-Teller analysis, field emission scanning electron microscopy and transmission electron microscopy. The synthesised spherical nanoparticles, at a specific size of 10-50 nm, possessed large surface areas of approximately 13.27 m2/g, reinforcing the significant advantages of EWE, that is, less aggregation and in situ production of nanoparticles with enhanced removal efficacy, for groundwater treatment. After 1 h the adsorption capacity for Cr(VI), Ni(II), and Cd(II) ( Q60 = Cions/ Ciron (mg/g)) at pH 4 was approximately 143.4 (89.0%), 137.5 (79.0%), and 132.6 mg/g (72.0%), respectively. The effect of temperature was also examined at initial metal ions concentration of 70 mg/L, nZVI dosage of 0.2 g/L and pH 4. The results showed 45°C was the optimum temperature for adsorption of Cr(VI), Ni(II), and Cd(II) ions, and over a 60-min period at this temperature adsorption capacity increased to 153.56 (95.3%), 158.91 (91.3%), and 163.90 mg/g (89.0%), respectively. [ABSTRACT FROM AUTHOR]

Environmental remediation technologies that involve the use of sulfate-reducing bacteria constitute a feasible alternative to the remediation of sites polluted with heavy metals and metalloids. The present study evaluates hydrogen sulfide production and arsenic removal by two microbial consortia (C1 and C2) in batch systems exposed to different arsenic concentrations and oxidation states. We identify the following three consecutive stages of arsenate removal: (1) hydrogen sulfide production/accumulation, (2) arsenate reduction to arsenite associated with the incomplete oxidation of hydrogen sulfide to elemental sulfur and (3) arsenic polysulfide precipitation as the main arsenic removal mechanism from aqueous solution. Kinetic parameters are determined in regard to the arsenic oxidation state through the fit of hydrogen sulfide production. The r reached by C1 and C2 is increased seven- or eightfold when 250 mM As[+5] was used instead 250 mM As[+3]. Arsenic removal by extracellular precipitation of arsenic polysulfides associated with elemental sulfur precipitation detected through scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS) can explain the exceptional value of r observed at 250 mM during As[+5] exposition. [ABSTRACT FROM AUTHOR]

This study was carried out to assess, for the first time, the effect of water treatment residual nanoparticles (nWTR) on mobility, fractionation and speciation of Hg in two arid zone soils. Nanoscale water treatment residual application markedly reduced cumulative Hg released from soils studied, with the effect increasing as the nWTR application rate increases. The power function kinetic model well described the desorption process from soils and soils with nWTR. Meanwhile, application of nWTR greatly increased the association of Hg with the residual fraction and increased the most stable Hg species (Hg (OH)2 amor), which in turn enhanced Hg immobilization in the studied soils. Fourier transmission infrared spectroscopy analysis indicated the involvement of nWTR in the retention of Hg (II) and revealed that sorption occurred mainly through OH groups, which suggest inner-sphere adsorption of Hg ions to surface functional groups on nWTR. These results demonstrated the feasibility of using a green and low-cost nWTR as best management practice to retain and immobilize excess Hg in contaminated soils. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A novel and recyclable poly(polyethylene glycol diacrylate/maleamic acid) (p(PEGDA/MALA)) copolymer hydrogel beads were for the first time synthesized through a microfluidic method and used for the removal of heavy mental ions from water. The monodisperse and size-controlled pregel droplets were firstly prepared by a microfluidic device and then polymerized to the hydrogel beads under UV irradiation. The synthesized p(PEGDA/MALA) hydrogel beads were characterized using various techniques and showed good adsorption property for Pb. The influencing factors on the adsorption process of Pb were investigated in detail. The experiment results indicated that Pb adsorption process was pH dependent, and agreed with the Langmuir monolayer model and pseudo-second-order equation. The adsorbing mechanism of copolymer hydrogel beads for Pb mainly resulted from the electrostatic interaction and chelation action. The competitive adsorption experiment indicated that the affinity order in multicomponent adsorption was Pb>Cu>Cd. The well-designed p(PEGDA/MALA) copolymer hydrogel beads had excellent adsorption capacity and high recyclability and showed a promising application prospect in the decontamination of heavy metal ions in water. [ABSTRACT FROM AUTHOR]

The current study focuses on plant promoting and metal detoxifying properties of a heavy metal resistant bacterium with phosphate (P) solubilizing and Indole-3-acetic acid (IAA) producing capabilities. The bacterium was a strain of Pseudomonas putida Ws3 selected from an agricultural land irrigated with sewage water. It could solubilize P up to 300 mg/l and produce IAA up to 200 µg/l in seven days at optimal culture condition, i.e. NaCl (0.5%), KCl (0.01–0.04%), Mg/Cl 2 (0.3%) and NH 4 Cl (0.5%) and 30 °C. Regarding soluble P and IAA concentrations in Pikovskaya (PVK) liquid media, the activity of the bacterium declined in media containing CuCl 2 (500 mg/l), PbCl 2 (300 mg/l) or CdCl 2 (300 mg/l). The metals at elevated levels limited the bacterial population growth in a soil-like substrate supporting roots of a model plant (maize or Zea mays ). Weekly bacterial inoculation to the substrate for 40 days alleviated the condition for plant growth, led to increased plant dry weight and decreased the metals accumulated in plant with large effect sizes in the shoot (g=1.49) and root (g=1.36). [ABSTRACT FROM AUTHOR]

There is increasing interest in using water treatment residuals (WTRs) for heavy metals removal from wastewater due to their low cost, availability, and high efficiency in removing various pollutants. In this study, novel water treatment residuals nanoparticles (nWTRs) were prepared using high energy ball milling and used for efficient removal of Cd(II) in single- and multi-ion systems. The WTR nanoparticles demonstrated high removal efficiency for Cd from aqueous solution as the adsorption capacities of nWTR were 17 and 10 times higher than those of bulk WTR in single- and multielement systems, respectively. Noticeably, Cd(II) adsorption was clearly suppressed in the multi-ion system as Cu and Pb form the most stable monohydroxo complexes. Fourier transmission infrared (FTIR) analyses suggested the participation of OH−, O-Al-O, FeOH, and FeOOH entities in the adsorption process. The stability of Cd-nWTR surface complexes is evident as less than 0. 2% of adsorbed Cd(ll) was released at the highest Cd(II) concentration load after 4 consecutive desorption cycles. Moreover, the real efficiency of nWTR for Cd(II) removal from wastewater samples studied was calculated to be 98.35%. These results highlight the potential of nWTR for heavy metals removal from wastewater. [ABSTRACT FROM AUTHOR]

A robust and water-stable metal-organic framework (MOF), featuring hexagonal channels decorated with methionine residues ( 1), selectively captures toxic species such as CH3Hg+ and Hg2+ from water. 1 exhibits the largest Hg2+ uptake capacity ever reported for a MOF, decreasing the [Hg2+] and [CH3Hg+] concentrations in potable water from highly hazardous 10 ppm to the much safer values of 6 and 27 ppb, respectively. Just like with biological systems, the high-performance metal capture also involves a molecular recognition process. Both CH3Hg+ and Hg2+ are efficiently immobilized by specific conformations adopted by the flexible thioether 'claws' decorating the pores of 1. This leads to very stable structural conformations reminiscent of those responsible for the biological activity of the enzyme mercury reductase (MR). [ABSTRACT FROM AUTHOR]

A low-cost and environmentally friendly calcium alginate aerogel (CAA) was prepared by freeze-drying method, characterized, and evaluated for removal of Pb 2+ from water. Experimental results indicate that the CAA shows high selectivity and adsorption capacity for Pb 2+ . Relative selectivity coefficients for Pb 2+ over other metal ions are all over 10. The CAA can also adsorb 96.4% of Pb 2+ in aqueous solution. The maximum adsorption capacity of CAA for Pb 2+ is 390.7 mg/g, which is higher than that of other reported adsorbents. Moreover, the CAA can be regenerated by simple acid treatment and used repeatedly without loss in performance. [ABSTRACT FROM AUTHOR]

This study demonstrated that soil washing using ethylenediaminedisuccinic acid (EDDS) as a chelating agent was efficient at removing copper and zinc from real polluted soils. Only the exchangeable and reducible fractions of Cu and Zn were extracted by EDDS. Intra-particle diffusion was the main rate controlling step in this extraction of heavy metals from the solid matrix. Different contributions were found by applying the Weber and Morris intraparticle diffusion model resulting from the different roles of superficial and intra-particle diffusive processes.The diffusion coefficients of the Cu/EDDS and Zn/EDDS complexes in real contaminated soils were estimated using simplified diffusive models (based on Crank’s and Vermeulen's approximations). The relationship between the grain size and diffusion coefficient was also evaluated. In particular, the intraparticle diffusion coefficients increased with increasing the particle size, thus indicating that the smallest granulometric fractions are characterized by a higher percentage of micropores than the largest fractions. [ABSTRACT FROM AUTHOR]

In order to determine the effect of a dam on metal concentrations in riverine fish species, we studied fish inhabiting the influent (Cachapoal River) and effluent (Rapel River) of the Rapel Reservoir in central Chile. Heavy metals were quantified in gills, liver and muscle of the catfish Trichomycterus areolatus and the silverside Basilichthys microlepidotus. Also, the bioaccumulation index (BAI) was estimated by considering heavy metal concentrations obtained from water and sediment. Results showed the presence of Al, Cu, Fe, Mn, Pb and Zn in the fish organs. The analysis showed high metal concentrations in catfish inhabiting the influent compared to those collected in the effluent. These results indicate a possible filter effect of the dam for most of the metals identified in the fish organs, because metal concentrations decreased in the effluent. Finally, catfish exhibited a larger BAI for most metals analyzed. [ABSTRACT FROM AUTHOR]

Heavy metals and Dyes are very toxic and nonbiodegradable in waste waters to cause adverse health effects in human body and to induce irreversible pollution. Adsorption offers many potential advantages for removal of toxic heavy metals being flexibility in design and operation, high-quality treated effluent, reversible nature for multiple uses, and many commercially available adsorbent materials, such as activated carbon, zeolite, clay, sawdust, bark, biomass, lignin, chitosan and other polymer adsorbents. Compared to conventional adsorbent materials above, hydrogelbased adsorbents recently have attracted special attention to their highly potential for effective removal of heavy metals and dyes. Hydrogels are named "Hydrophilic Polymer" because of care for water. Hydrogels is not solved in water; however they have been swollen to their balance volume. Because of this swell behavior, they can adsorb big quantity of water in this structure. So they can term of "three sized polymers" due to protect their existing shape [9]. Hydrogels with porous structures and chemically-responsive functional groups, enable to readily capture metal ions and dyes from wastewater. Hydrogels with porous structures and chemically-responsive functional groups, enable to readily capture metal ions and dyes from wastewater. In adsorption applications, hydrogels are used in water purification, heavy metal/dying removing, controlled fertilizer released, ion exchange applications, chromatographic applications, dilute extractions, waste water treatments. This article general inform about usage of hydrogels in Dye and Heavy Metal adsorption. [ABSTRACT FROM AUTHOR]

Nanosilica particles modified by Schiff base ligands 3-methoxy salicylaldimine propyl triethoxysilane (MNS), 5-bromo salicylaldimine propyl triethoxysilane (MNS) and 3-hydroxy salicylaldimine propyl triethoxysilane (MNS) were prepared, and their potential for separation of copper, lead, zinc, cadmium, cobalt and nickel ions from aqueous solutions was examined. The effect of parameters influencing adsorption efficiency including aqueous-phase pH, amount of adsorbent, stirring time and initial concentration of the metal ions was assessed and discussed. Although MNS and MNS removed lead ions efficiently, all adsorbents showed strong selectivity toward copper ions. It was shown that, under some circumstances, MNS decreased the amount of other ions, particularly cobalt, in the aqueous phase. The adsorbents were also applied for removal of copper and lead ions from real samples. Possible quantitative desorption of the metal ions loaded onto the adsorbents suggests their multiple uses in adsorption-desorption process. Investigation of temperature dependency of the process led to determination of the Δ H°, Δ S° and Δ G° values. This investigation indicates that the adsorption of copper ions onto the all studied adsorbents and lead ions onto MNS and MNS is endothermic. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms were tested to describe the equilibrium data. Pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion equations were applied to study the kinetics of copper and lead adsorption onto the modified nanoparticles. This investigation indicates that the process for all adsorbents follows pseudo-second-order kinetics and suggests a chemisorption mechanism for the adsorption processes by the studied adsorbents. [ABSTRACT FROM AUTHOR]

In this research, an infiltration trench equipped with an extensive pretreatment and filter bed consisting of woodchip, sand and gravel was utilized as a low impact development technique to manage stormwater runoff from a highly impervious road with particular emphasis on heavy metal removal. Findings revealed that the major factors influencing the removal of heavy metals were the concentration of the particulate matters and heavy metals in runoff, runoff volume and flow rates. The reduction of heavy metals was enhanced by sedimentation of particulates through pretreatment. Fine particles (<2 mm) had the most significant amount of heavy metals, thus, enhanced adsorption and filtration using various filter media were important design considerations. Sediment was most highly attached on the surface area of woodchip than to other filter media like sand, gravel and geotextile. It is suggested that maintenance must be performed after the end of the winter season wherein high sediment rate was observed to maintain the efficiency of the treatment system. [ABSTRACT FROM AUTHOR]

Peanut hull is a local natural abundant agricultural waste in Egypt. The peanut hull was used as an adsorbent without any chemical or physical treatment for copper ions Cu(II) removal from aqueous solutions. Effects of various parameters such as contact time, particle size and dosage of adsorbent, initial pH, solution temperature, and initial concentration of Cu(II) were investigated for a batch adsorption system.The optimum operating conditions were (1 h, 150 rpm shaking speed, 25 °C, pH = 4, 1 g peanut hulls of particle size < 250 μm/50 ml of 150 ppm cupper ions solution concentration). The maximum adsorption capacity was 14.13 mg/g peanut hulls. Several kinetic models have been investigated to recognize the cupper ions adsorption mechanism onto peanut hulls. The results showed that the adsorption process obeyed the pseudo-second-order and intra-particle diffusion kinetic models, pointing that the adsorption mechanism is chemical and physical adsorption process. Langmuir and Freundlich adsorption isotherms have been investigated. The thermodynamic parameters have been studied, and it proved that, adsorption of Cu(II) using peanut hulls is endothermic and nonspontaneous. This study convinced that the naturally peanut hulls proved to be an alternative, attractive, effective, economic, and environmentally friendly adsorbent for Cu(II) removal from aqueous solution. [ABSTRACT FROM AUTHOR]

In order to use biosurfactants to desorb metals from biosorbents without changing their adsorption capacity, there is a need to determine conditions of process. In this study, we examined the kinetics of desorption of cadmium, zinc, and copper and their mixtures from activated sludge immobilized in 1.5% sodium alginate with 0.5% polyvinyl alcohol. Metals leaching from immobilized biomass were analyzed with the use of three biosurfactants—saponin, JBR 515, JBR 425, and nitric acid. Desorption effectiveness of single metals and their mixtures was also investigated as influenced by different desorption parameters such as pH, contact time, and dose of desorbents. The obtained values of kinetic constants of pseudo-first-order (k1) and pseudo-second-order (k2) showed that in case of all analyzed desorbents, the process of metals leaching from immobilized activated sludge proceeded according to the pseudo-second-order reaction as indicated by theR2values. Out of the analyzed desorbents, saponin and nitric acid proved to be the most effective in leaching both individual metals and their mixtures from the biosorbent. Saponin showed high leaching effectiveness in a pH range of 1–5, whereas the optimal conditions for nitric acid were at pH 1–2. The effectiveness of metals desorption from biosorbent using saponin reached 94.8% (Zn), 86.6% (Cu), and 51.2% (Cd) (a solution of single metal) and 92.7, 73.6, and 43.1%, respectively, for a solution of metal mixture. These results show that saponin is an attractive and environmentally friendly desorbent for the removal of metals and their mixtures from biosorbent. [ABSTRACT FROM PUBLISHER]

The tendu (Diospyros melanoxylon) leaves as refuse from bidi industry, contaminate the environment by its disposal and its degradation period is so long compared to other leaves. Adsorption process is carried out in shake flask condition using carbonized tendu leaf refuse as a adsorbent. The results obtained by the process of biosorption using tendu leaf for synthetic effluent show that the maximum efficiency achieved is 99.5% for chromium and 95% for copper at pH 5. In relation to electroplating effluent, the removal efficiency of chromium is 97%, copper is 96%, cadmium 81% and magnesium 75%. From electroplating effluent contaminated soil, the leachate was collected. 100% removal efficiency of all metals is noted. The isothermal studies showed good result for pH 5 and pH 7. The Langmuir isotherm fits to the data of the present study better than the Freundlich isotherms. Also the exprimental data follows pseudo-first order reaction. [ABSTRACT FROM AUTHOR]

Diplotaxis harra biomass was used as a precursor for the preparation of activated carbons by phosphoric acid activation. The effects of several factors controlling the activation process, such as carbonization temperature (500–600 °C), activation temperature (400–500 °C), activation time (1–2 h) and impregnation ratio (g H 3 PO 4 /g carbon) (1.5–2) were established. In order to reduce the number of experiments, full factorial experimental design at two levels (2 4 ) were carried out to achieve optimal preparation conditions and better conditions for the removal of cadmium and cobalt ions from aqueous solutions. The experimental results showed that the carbonization temperature was more significant with a negative effect for iodine number and methylene blue index. Therefore, activation temperature and activation time present a positive effect for iodine number and negative effect for methylene blue index. The impregnation ratio shows a positive impact for the both indicated responses. The removal of cadmuim and cobalt ions onto activated carbons was more sensitive to methylene blue index. Moreover, the interaction between carbonization and activation temperatures was the most influencing in cadmium and cobalt ions removal with a positive effect. Using this statistical tool, the best conditions for the removal of cadmium and cobalt by Diplotaxis Harra based activated carbons were established. The maximum iodine number and methylene blue index obtained under these experimental conditions were 1058.8 mg/g and 280.4 mg/g respectively. The high sorption capacities were 31.6 mg/g for cadmium and 25.9 mg/g for cobalt. Those characteristics were shown close than those of a commercial activated carbon used in water treatment and those reported by other researchers studying activated carbon preparation from various solid wastes. [ABSTRACT FROM AUTHOR]

For the development of decentralized treatment systems for road runoff, the determination of pollutant removal capacities is essential. The aim of this study was to evaluate the impact of boundary conditions on the simultaneous removal of copper, nickel, and zinc by six sorbents used for urban stormwater treatment (i.e., granular activated alumina, anthracite, granular reactivated carbon, granular ferric hydroxide, calcium carbonate, and granular activated lignite). For batch experiments, capacities were determined at initial concentrations within the range of 2.5-180 mg/L with a rotary shaker. Further influences were investigated: the use of a horizontal shaker for concentrations of up to 1080 mg/L, a variation of the initial pH value (5 and 7), and the presence of a buffer. Furthermore, the influences of the filtration process on the capacities were studied. Kinetic experiments were conducted for contact times between 5 min and 120 min. Lab-scale column experiments with inflow concentrations of 2.5 mg/L (copper and nickel) and 5.0 mg/L (zinc) at an initial pH of 5 and a contact time of 11 min were performed for comparison. Selected experiments were subsequently carried out with changes in initial concentrations and contact time. One result is that it is essential to conduct batch experiments with the metals of interest. The capacities determined by column experiments deviated from batch experiments. Batch experiments under well-defined conditions can be used to evaluate different production batches. Column experiments give a more faithful capacity by considering realistic boundary conditions and should be preferred to determine efficiencies and service lives. [ABSTRACT FROM AUTHOR]

This paper physically and numerically models the influence of biofilms on heavy metal removal in a gravel filter. Experimental flow columns were constructed to determine the removal of Cu, Pb and Zn by gabbro and dolomite gravel lithologies with and without natural biofilm from sustainable urban drainage systems (SuDS). Breakthrough experiments showed that, whilst abiotic gravel filters removed up to 51% of metals, those with biofilms enhanced heavy metal removal by up to a further 29%, with Cu removal illustrating the greatest response to biofilm growth. An advection–diffusion equation successfully modelled metal tracer transport within biofilm columns. This model yielded a permanent loss term (k) for metal tracers of between 0.01 and 1.05, correlating well with measured data from breakthrough experiments. Additional 16S rRNA clone library analysis of the biofilm indicated strong sensitivity of bacterial community composition to the lithology of the filter medium, with gabbro filters displayingProteobacteriadominance (54%) and dolomite columns showingCyanobacteriadominance (47%). [ABSTRACT FROM AUTHOR]

Summary Concentrations of dissolved metals in stormwater runoff from urbanized watersheds are much higher than established guidelines for the protection of aquatic life. Five potential soil amendment materials derived from affordable, abundant sources have been tested as filter media using shaker tests and were found to remove dissolved metals in stormwater runoff. Blast furnace (BF) slag and basic oxygenated furnace (BOF) slag from a steel mill, a drinking water treatment residual (DWTR) from a surface water treatment plant, goethite-rich overburden (IRON) from a coal mine, and woodchips (WC) were tested. The IRON and BOF amendments were shown to remove 46–98% of dissolved metals (Cr, Co, Cu, Pb, Ni, Zn) in repacked soil columns. Freundlich adsorption isotherm constants for six metals across five materials were calculated. Breakthrough curves of dissolved metals and total metal accumulation within the filter media were measured in column tests using synthetic runoff. A reduction in system performance over time occurred due to progressive saturation of the treatment media. Despite this, the top 7 cm of each filter media removed up to 72% of the dissolved metals. A calibrated HYDRUS-1D model was used to simulate long-term metal accumulation in the filter media, and model results suggest that for these metals a BOF filter media thickness as low as 15 cm can be used to improve stormwater quality to meet standards for up to twenty years. The treatment media evaluated in this research can be used to improve urban stormwater runoff discharging to environmentally sensitive areas (ESAs). [ABSTRACT FROM AUTHOR]

In this study, the influence of the heavy-metal-resistant rhizobacterial inoculant Rhodococcus ruber N7 on the growth and enzyme activity of Sorghum bicolor (L.) Moench. under cadmium stress was investigated in quartz sand pot experiments. The effect of cadmium and bacterium on the plant biomass accumulation, photosynthetic pigments, protein content, and the activities of plant-tissue enzymes such as peroxidase, laccase, and tyrosinase were estimated. It was shown that the presence of cadmium in the sand influenced the roots to a greater extent than it influenced the aerial parts of sorghum. This is manifested as increased protein content, reduced activity of peroxidase, and increased activity of laccase. Compared with cadmium stress, inoculation of plants with rhizobacterium R. ruber N7 has a stronger (and often opposite) effect on the biochemical parameters of sorghum, including a decrease in the concentration of protein in the plant, but increased the activity of peroxidase, laccase, and tyrosinase. Under cadmium contamination of sand, R. ruber N7 successfully colonizes the roots of Sorghum bicolor, survives in its root zone, and contributes to the accumulation of the metal in the plant roots, thereby reducing the concentration of the pollutant in the environment. [ABSTRACT FROM AUTHOR]

A 2-compartment electrodialytic cell set-up for treatment of solid materials has in many respects proven superior to other types of cells in removing heavy metals from sediments. Most notably, remediation times were shorter, energy consumption was lower and higher removal efficiencies were observed. By employing m1ultivariate modelling and investigating additional experimental variables, the relative importance of variables effecting remediation was determined and response surfaces for heavy metal removal were calculated. Employing optimal conditions it was possible to remove targeted metals (Pb, Cu, Zn), by 73–96 %, and remediation objectives could be met in a large region of the studied experimental domain. [ABSTRACT FROM AUTHOR]

In this paper, the ability of granular activated carbon (GAC), silica spongolite (SS) and zeolite (Z) to remove heavy metals from aqueous solutions has been investigated through column tests. The breakthrough times for a mobile tracer that does not sorb to the material for SS, GAC and layered SS, Z and GAC were as follows: 2.54×104 s, 2.38×104 s and 3.02×104s. The breakthrough time (tbR) for Ni was in the range fromtbR = 1.70×106 s for SS, throughtbR = 3.98×105 s for the layered bed, totbR = 8.75×105 s for GAC. The breakthrough time for Cd was in the range fromtbR = 1.83×105 s for GAC totbR = 1.30×106 s for SS, Z, GAC. During the experiment, the concentration of Cd, Cu, Pb and Zn in the solution from a column filled with construction aggregate and the concentration of Pb, and Cu in a filtrate from the column filled with several materials was close to zero. The reduction in metal ions removal was due to high pH values of the solution (above 8.00). In addition, during the testing period, an increase in Cd and Zn concentrations in the filtrate from the column filled with the layered bed was observed, but at the end of the experiment the concentrations did not reach the maximum values. The test results suggest that the multilayered permeable reactive barrier is the most effective technology for long time effective removal of heavy metals. [ABSTRACT FROM AUTHOR]

A vast array of industrial waste products, agricultural by-products, and biological materials, such as bacteria, algae, yeasts, and fungi have received increased attention for heavy metal removal and recovery due to their good performance, low cost, and availability in large quantities. Such materials are cheaper, more effective alternatives to commercial activated carbon (AC) for the removal of heavy metals from aqueous solution. The authors review in greater detail the various factors affecting the adsorption capacity and cost efficiency based on the literatures and present research results. Special emphasis has been made on nature of the precursors, their pretreatment and modification, the activation conditions of time and temperature, pH of aqueous media, and regeneration/reuse potential. The authors present some of the latest important results and give a source of up-to-date literature on the ACs prepared from various low-cost precursors from agro-industrial wastes as well as from biological materials. The evolution of adsorption has turned from an interesting alternative approach into a powerful standard technique by offering a numbers of advantages: better performance in terms of ulterior adsorption capacity, rate of adsorption, solving wastewaters pollution in a cost-effective way, and overcoming part of the solid wastes problem around the world. Various advantages and challenges have been identified and a widespread and great progress in this area can be expected in the future. [ABSTRACT FROM PUBLISHER]

The concentration decay curves for the adsorption of lead on a granular activated carbon from coconut shells are obtained in an agitated batch adsorber. The experimental adsorption rate data are modeling using a complex diffusional model which takes into account adsorption, external mass transfer and intraparticle diffusion. It is assumed that the intraparticle diffusion is due to pore volume diffusion and surface diffusion. The external mass transfer coefficient is estimated from the initial slope of the concentration decay curve. The effective diffusion coefficients are evaluated by matching the experimental concentration decay data with a numerical solution of the mathematical model. The pore volume and surface diffusion model adjusts the data quite well. The results indicate that intraparticle diffusion controls the whole process, diffusion is predominantly due to pore volume diffusion and surface diffusion is negligible. The logarithm of the pore volume diffusion coefficient is linearly dependent upon the inverse of the temperature, upon the initial pH and upon the maximum amount of lead adsorbed by the activated carbon. The external mass transfer and the pore volume diffusion coefficients increase with the initial temperature, with the initial pH, decrease with the lead initial concentration and pass through a maximum with the adsorbent dose. [ABSTRACT FROM AUTHOR]

Polyethersulfone membranes with integrated negatively-charged hydrogel of crosslinked poly(acrylamido-2-methylpropane sulfonic acid) were prepared by a combination of a liquid phase inversion process with photopolymerization and crosslinking of functional monomers included in the casting solution. A designed experiment was conducted to select the optimal composition for preparing membranes with a sufficient degree of swelling and ion exchange capacity. Scanning electron microscopy images revealed an ultrafine hybrid structure with an interconnected network of submicron particles embedded within the microporous polyethersulfone support. An intramembrane diffusion model was used to describe kinetics of heavy metal sorption by these hydrogels and the calculated apparent diffusion coefficients were 2–3 times larger than in commercial ion-exchange resins. Equilibrium sorption of heavy metals was described using a semi-empirical Langmuir model. [ABSTRACT FROM AUTHOR]

Heavy metals in sludge are of great concerns worldwide due to their high toxicity. The toxicity of heavy metals strongly depends on their stability in the sludge. This study investigated the stability of typical sludge heavy metals (As, Cd, Cr, Cu, Ni, Hg, and Pb) during ultrasonic sludge treatment process. Results showed that sonication enhanced the stability of sludge heavy metals, which was beneficial for sludge disposal and reclamation. Content of stable fractions increased and content of unsteady fractions decreased after 15-min sonication at 2.0 WmL−1. The stability of each heavy metal in sludge was significantly different during sonication. For arsenic, unsteady fractions decreased from 94 to 9% and stable fractions increased from 0 to 68% after 15-min sonication; for mercury and lead, stability showed little change due to the high residual fraction. Sonication changed the stability order of heavy metals in sludge. In the untreated sludge, the stability order was As < Ni < Cd < Cu < Cr < Pb < Hg; after 15-min sonication, the order was Cd < Ni < Cu < Cr < As < Pb < Hg. [ABSTRACT FROM PUBLISHER]

Three bacterial species of PG01, PG02, and PG03 were isolated from coastal sediments of Bushehr (Iran) as mercury-resistant bacteria. According to 16S ribosomal DNA gene sequence, the strains were identified as Vibrio natriegens, Vibrio parahaemolyticus, and Oceanimonas baumannii, respectively. Minimum inhibitory concentration test in the presence of HgCl2 revealed that the strain PG02 was the most resistant one, which tolerated up to 45 mg L−1 Hg2+. Tracing the growth curves for the PG02 showed that when it is initially exposed to 5 mg L−1 Hg2+ in the medium, only 10% of its natural growth is reduced, while it simultaneously succeeds to remove 90% of mercury. However, initially 10 mg L−1 Hg2+ in the medium led to 30% growth inhibition and 80% mercury removal. According to a linear relationship between the growth inhibition percentage and the initial mercury concentrations, the median effective concentration was calculated as 21.84 mg L−1 for PG02. Central composite design under response surface methodology well proposed a model with high values of R2 = 0.999 and adjusted R2 = 0.998 which predicted the maximum mercury removal of 89.47% by PG02 under optimum pH of 7.2, temperature of 37.5°C and the initial mercury concentration of 5 mg L−1. [ABSTRACT FROM AUTHOR]