Concentrations Of Heavy Metal Ions Research Articles

Steel slag as a potential adsorbent for efficient removal of Fe(II) from simulated acid mine drainage: adsorption performance and mechanism.

Acid mine drainage is an extraordinarily acidic and highly heavy metal ion-contaminated leachate, seriously threatening the environment. In this work, an industrial solid waste of steel slag is the adsorbent to remediate the simulated acid mine drainage containing a large amount of Fe(II) ions. Due to the excellent physicochemical properties and structures, steel slag exhibited remarkable Fe(II) removal performance. Its maximum removal efficiency was up to 100%. The initial pH, the dosage and particle size of steel slag, and initial concentration of heavy metal ions on Fe(II) removal efficiency were determined. The pseudo-second-order model and Freundlich isotherm model well described the adsorption behavior of steel slag, implying that the adsorption of Fe(II) by steel slag was mainly multilayer chemisorption. The thermodynamic study demonstrated that the adsorption process was endothermic and spontaneous; the enthalpy change was calculated to equal 91.21kJ/mol. Mechanism study showed that the entire removal process of Fe(II) by steel slag was completed by electrostatic adsorption, chemical precipitation, and surface complexation in cooperation, and the chemical precipitation was the dominant mechanism. Meaningfully, this study provides a valuable strategy and path for engineering applications of AMD remediation by steel slag, which is prospective as an ideal candidate for Fe(II) ions elimination, inspiring the future development of "Treating the wastes with wastes."

Functionalized halloysite nanotubes incorporated thin film nanocomposite nanofiltration membrane for treatment of wastewaters containing metal ions

The high concentrations of heavy metal ions in industrial effluents are one of the most challenging wastewaters to deal with. In this study and in order to change the inner diameter of the halloysite nanotubes (HNT), their internal surface was coated by different polymers (polydopamine, polyaniline and polystyrene) and then, the modified nanotubes were incorporated in the polyamide thin film NF membrane for the treatment of metal ions solutions. Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) studies indicated that the internal coating was successful. Furthermore, the neat and modified nanofiltration (NF) membranes were characterized in terms of morphology, contact angle, water flux and metal ion rejection. The modified membranes displayed lower contact angle values (29.4% reduction) that can be linked to the hydrophilic groups in the structure of the coated polymers and the smoother surface of the thin film nanocomposite (TFN) membrane. In addition, the permeation fluxes of the modified membranes were improved significantly (33.4% improvement) without any major reduction in their ion rejection; that shows HNTs act as the channels to transfer water through the membrane structure while the coating of the inner surface of HNT reduces the size of the channel and makes more repulsion and steric hindrance for the ion to pass through the nanotubes. Among the fabricated membranes, the NF membrane with 0.05 wt% polystyrene-coated HNT showed the lowest contact angle (55.30o) and the highest water permeation flux (27.51 L m-2 hr-1), compared to the neat TFC membrane (15.26 L m-2 hr-1) and the NF membrane with 0.05 wt% unmodified HNT (20.62 L m-2 hr-1).

Functionalized Activated Carbon Derived from Palm Kernel Shells for the Treatment of Simulated Heavy Metal-Contaminated Water.

Heavy metal contamination in water poses a great risk to human health as well as to the lives of other creatures. Activated carbon is a useful material to be applied for the treatment of heavy metal-contaminated water. In this study, functionalized activated carbon (FAC) was produced by the induction of nitro groups onto activated carbon using nitric acid. The resulting material was characterized in detail using the XRD, Raman, BET, FTIR, and FESEM techniques. The FAC was used for the treatment of heavy metal-contaminated water using different adsorption parameters, i.e., solution pH, contact time, adsorbent dosage and heavy metal ion concentrations, and these parameters were systematically optimized. It was found that FAC requires 90 min for the maximum adsorption of the heavy metal ions; Cr6+, Pb2+, Zn2+ and Cd2+. The kinetic study revealed that the metal ion adsorption follows the pseudo-second-order. The Freundlich and Langmuir isotherms were applied to determine the best fitting adsorption isotherm models. The adsorption capacities were also determined for each metal ion.

Alternative treatment for metal ions removal from acid mine drainage using an organic biomixture as a low cost adsorbent

Acid mine drainage, characterized by low pH and elevated heavy metal ion concentrations, causes severe harm to the environment. In this study, the feasibility of a new organic biomixture adsorbent for removing Fe3+, Zn2+, Cu2+ and Mn2+ metal ions from synthetic acid mine drainage was evaluated. This kinetic study showed fast metal ions adsorption within the first four to eight hours, and adsorption over 80% in the organic biomixture. The equilibrium adsorption isotherms resulted in a metal ion uptake greater than 84%, and the Freundlich model fitted well the data. The Freundlich affinity coefficient (Kf) ranged from 1.44 to 3.82 in the following order: Zn2+>Cu2+>Fe3+>Mn2+. Scanning electron microscope images revealed the heterogeneous structure of the biomixture, and energy-dispersive X-ray analysis after adsorption confirmed the ability of the biomixture to remove the metal ions. In the fixed-bed column, the Thomas model described (R2>0.95) the adsorption process of metal ions contained in the treated acid mine drainage well. The adsorption capacity (q0) of this system resulted in 164.2 mg g−1, 129.2 mg g−1, 26.0 mg g−1 and 15.3 mg g−1 of Fe3+, Zn2+, Cu2+ and Mn2+, respectively. This study confirmed the efficiency of an organic biomixture to adsorb metal ions and provide new and valuable information for the future design of low-cost treatments to reduce acid mine drainage pollution.

Adsorption Features of Loess Calcareous Nodules to Heavy-Metal Ions in Aqueous Solution

This paper explores the use of calcareous tuberculosis as an adsorbent and heavy-metal ions (Cu2+, Zn2+, Cd2+, and Pb2+) as adsorbates, and the influence of varying levels of particle size, adsorption time, pH, adsorbent dosage, and initial concentration of heavy metals is studied through an experiment of single heavy-metal adsorption. In addition, the impact of the temperature and other factors on the adsorption of heavy-metal ions by calcareous nodules is analyzed to identify the optimal conditions for the adsorption of heavy-metal ions by calcareous nodules. As shown by the research findings, the adsorption rates of Cu2+, Zn2+, and Pb2+ gradually declined with the increase in particle size, with no evident effect on Cd2+. In the meantime, with further increases in factors such as the adsorption time, adsorbent dosage, and temperature, the adsorption rates of Cu2+, Zn2+, Cd2+, and Pb2+ experienced gradual increases. The adsorption rates of Cu2+, Zn2+, and Cd2+ gradually declined with the increase in initial concentration of heavy-metal ions, whereas the adsorption rate of Pb2+ experience increased first and then declined. As the pH increased, the adsorption rate of Cd2+ experience increased first and then declined at a slow pace. The adsorption rates of Cu2+, Zn2+, and Pb2+ increased first and then decreased. The adsorption capacity of calcareous nodules toward the four heavy-metal ions was in the order of Pb2+ > Zn2+ > Cu2+ > Cd2+. When the particle size was set to 0.25 mm, the adsorption time was set to 120 min, and the dosage was set to 0.6 g, the calcareous nodules included Pb2+, Zn2+, and Cu2+. Moreover, Cd2+ was able to achieve stronger adsorption capacity, with the adsorption rate able to reach 83.33%, 77.78%, 73.81%, and 81.93% of its maximum level. Therefore, as the particle size of the heavy-metal ions decreased, the adsorption capacity generally became stronger. As the adsorption time increased, the temperature and the amount of adsorbent also increased. The optimal pH value for the adsorption of calcareous nodules toward Pb2+, Zn2+, Cu2+, and Cd2+ was found to be 7, 6, 5, and 8, respectively, and the optimal temperature was 50 °C. In summary, calcareous nodules are a natural, low-cost, and effective adsorbent.

Adsorption of lead, copper and zinc in a multi-metal aqueous solution by waste rubber tires for the design of single batch adsorber

Heavy metal pollution has emerged as one of the most serious environmental challenges facing the world today. The removal of heavy metals from the effluent is of special environmental concern because of their toxicity and persistence in nature. This study presents the suitability of activated carbon from waste rubber tire as a low-cost adsorbent for multiple adsorption of copper, lead and zinc from wastewater. The adsorbent removed heavy metal ions effectively from solution medium in the order of copper > lead > Zinc. The adsorption process was rapid with all metals reaching equilibrium within 120 min. The optimum pH for Lead was achieved at 5 and 6 for copper and Zinc. The removal of heavy metals was discovered to increase with adsorbent dosage and contact time and reduced with initial concentration. The adsorption of multiple heavy metals was modeled using Freundlich and Langmuir adsorption isotherms to assess the experimental findings. The equilibrium data better fitted to the Langmuir isotherm with regression coefficient (R2) of 0.9831, 0.9992 and 0.9953 for lead, copper and zinc respectively. The maximum adsorption capacities (Qmax) at equilibrium were 9.6805 mg/g, 12.4378 mg/g and 4.9950 mg/g for Lead, Copper and Zinc respectively. The adsorption kinetics indicated that pseudo-second-order kinetic model described well the sorption mechanism for multiple adsorption of heavy metals with R2 of more than 0.99 for all metal ions. An empirical model for predicting and designing of a single batch adsorber for 95 % multiple heavy metal ion removal at any given initial heavy metal ion concentration and effluent volume was further developed using activated carbon from waste rubber tires. Waste rubber tire Activated carbon demonstrated an ability for the treatment of wastewater containing these heavy metals in multimetal solutions.

Surface functionalization of mesoporous silica with maltodextrin for efficient adsorption of selective heavy metal ions from aqueous solution

A simple non-hydrothermal method for the synthesis of maltodextrin functionalized SBA-16 (SBA-16@MD) is reported for selective adsorption of heavy metal ions (HMIs) including Cd2+, Zn2+, and Cu2+ from aqueous solution. The as-synthesized SBA-16@MD is fully characterized by FESEM, EDX, HRTEM, PXRD, solid-state 13C NMR spectrum, TGA, and BET surface area measurement. The HMIs adsorption was investigated for several parameters, for example, HMIs concentration, adsorbent dose, temperature, pH, contact time, and stirring speed. The SBA-16@MD shows high values of adsorption capacity for Cd2+ (575.53 mg/g), Zn2+ (564.67 mg/g), and Cu2+ (509.73 mg/g) respectively, at pH 6. The calculated adsorption data are best fitted with the Langmuir isotherm inferring homogeneous HMIs adsorption on the surface of SBA-16@MD. The kinetic data are consistent with the pseudo-second-order and intraparticle diffusion models. The calculated thermodynamic data reveals that the nature of adsorption is endothermic and spontaneous. The high values of adsorption capacity, SBA-16@MD for Cd2+, Zn2+, and Cu2+ can be explained based on electrostatic interactions and ion exchange taking place between the SBA-16@MD surface and HMIs.

Determination of Pb(II) ion Adsorption Isotherm Model by Regenerated Spent Bleaching Earth (RSBE)

Waste water from several industries such as paint plant, printing, tin smelting, plastic factory, also fuel leaking from ships and ship welding are the main causes of the presence of Pb(II) ions in the water. Lead is a heavy metal that can adversely affects all organisms in the waters and can accumulate in the food chain, it is harmful to human and animal if exposed to it. Adsorption is one of the technologies for separating dissolved metal ions in liquid that easy handling and very effective. The concentration of heavy metal ions in solution can be reduced by using a adsorbent, such as zeolte, activated charcoal, regenerated spent bleaching earth (RSBE). Spent bleaching earth (SBE) is a disposal from edible of the bleaching unit in oil refinery industries, it can be regenerated to a adsorbent RSBE. The treatment SBE into RSBE, oil of SBE is separated by the solvent extraction method at 72°C for 5 hours with n-hexane as a solvent, followed by washing it with HCl 3%, then physically activated at 470°C for 12 hours. The goal of this study are to increase SBE value and reduce the level of Pb(II) ions in solution with RSBE. Several works done in this study, namely characterization of SBE and RSBE, determination of the absorption capacity of RSBE against Pb (II) ions at equilibrium conditions, and an adsorption isotherm model of Pb (II) ion by RSBE. Results, RSBE has a specific surface area of 165.88 m2/g, a total pore volume of 0.21 cc/g with an average pore diameter of 6.90 nm. Based on these values, RSBE is categorized as a mesoporous adsorbent. The adsorption of Pb (II) ion by RSBE reaches equilibrium after 150 minutes contact time.The adsorption Pb (II) ion by RSBE is follows the Langmuir isotherm adsorption model with a correlation coefficient (R2) value of 0.9935 and a maximum adsorbing capacity value of 4.29 mg Pb (II)/g RSBE.

MICROBIOLOGICAL AND SANITARY - CHEMICAL CHARACTERISTICS OF WASTEWATER FROM PHARMACEUTICAL COMPANY

Aim. Оssessment of wastewater from a pharmaceutical company according to sanitary-microbiological and chemical indicators to determine the method of treatment and remediation of them from pollutants and pathogens. Methods. In sanitary and bacteriological studies, classical microbiological methods were used to determine the total microbial number of pathogenic bacteria. Determination of the concentration of ammonium, nitrite and nitrate in wastewater samples from a pharmaceutical company was carried out spectrophotometrically using the chemical reaction of ions to Nessler's reagent, Griss reagent, and phenol sulfide acid. The content of heavy metal ions was determined by the method of electrothermal AAS using the device "Saturn-2", by the photometric method using 4-aminoantipyrine – phenol, by the extraction-photometric method – by surfactants, by the method of infrared spectrometry – by petroleum hydrocarbons. Results. It was experimentally confirmed that the total microbial count in wastewater samples from a pharmaceutical company slightly exceeded the standard value. The BGKP index and the E. coli index were within the normal range. The pathogenic bacteria Salmonella moscow and Klebsiella pneumoniae were found in the wastewater of pharmaceutical company. The contamination of pharmaceutical stock can be judged by the 8.5 times excess of the concentration of ammonium ions in them compared to the MPC. The results of chemical analysis of wastewater samples from a pharmaceutical company indicate their multicomponent composition.Of the heavy metal ions, ions of zinc, copper, lead, hexavalent chromium and cadmium were mainly detected. With the exception of cadmium ions, the concentration of heavy metal ions was 1.4–7.2 times higher than the MPC norm. Anionic surfactants predominated in pharmaceutical stocks – their concentration was 8.2 ± 0.7 mg/dm3. The level of phenolic and oil pollution of wastewater was minimal in comparison with the content of anionic surfactants, which could be caused by the activity of aboriginal strains of bacteria-destructors with a high phenolic capacity. Conclusion. The results of sanitary-microbiological and chemical analysis of wastewaters of a pharmaceutical company indicate their multicomponent nature and environmental hazard – they contain pathogenic bacteria Salmonella moscow and Klebsiella pneumoniae and pollutants of various nature: heavy metal ions Cu (II), Cr (VI) and Pb (II) at a concentration of 36.0 ± 14 μg/dm3, 3.0 ± 0.4 μg/dm3 and 14.0 ± 0.7 μg/dm3, respectively, and organic pollutants – phenol, oil products and anionic surfactants at a concentration of 0.003 ± 0.0006 mg/dm3, 0.81 ± 0.05 mg/dm3 and 8.2 ± 0.7 mg/dm3, respectively. Werecommend to carry out a comprehensive purification of wastewater from a pharmaceutical company from phenol, heavy metal ions [Cu (II), Cr (VI), Zn (II)], oil products, anionic surfactants and pathogens.

Research of heavy metals leaching from sediments after feritization processing of galvanic sludge

Possibility of environmental safety increasing for industrial enterprises as a result of resource-saving technology implementation for processing galvanic sludge is considered. An experimental study of stability for sediments after ferritization processing of galvanic sludge and exhausted technological solutions was carried out. As a result of dynamic leaching of heavy metal ions, the immobilization properties of sediments were determined, which were obtained at different technological parameters of the ferritization process. It is shown that the level of immobilization of heavy metals in ferritic sediments has significantly higher values in comparison with sediments of traditional wastewater neutralization. It was found, that the precipitate obtained at following key parameters of reaction mixture for the ferritization process: the total concentration of heavy metal ions 10.41 g/dm3; ratio of concentrations of iron ions to total concentration of other heavy metals ions 4/1 and pH value of 10.5, is characterized by the highest degree of immobilization of heavy metals in the sediments of 99.96% mass. Using the results of a complete factorial experiment, regression equation for the leaching of heavy metal ions (iron, nickel, copper and zinc) from ferrite sediments was obtained: ratio of iron concentrations to the total concentration of other heavy metals and the pH value of reaction mixture. The adequacy of coefficients of regression equations was evaluated according to the criteria of Student and Fisher, which with 95% reliability correspond to the experimental results of the study. The proposed calculation algorithm provides an opportunity to increase efficiency and automation of ferritization process. Subsequent use of the research results will allow to implement reliable utilization of ferritized galvanic waste by application them into the row materials for obtaining alkaline cements for special purposes.

Preparation of EDTA modified chitooligosaccharide/sodium alginate/Ca2+ physical double network hydrogel by using of high-salinity oilfield produced water for adsorption of Zn2+, Ni2+ and Mn2+

A novel EDTA functionalized chitooligosaccharide/sodium alginate/Ca2+ physical double network hydrogel (ECSDNH) was prepared by using of high-salinity oilfield produced water. The formation and structure of ECSDNH were characterized by FT-IR and SEM. Various factors, including EDTA functionalized chitooligosaccharide content, pH of solution, initial concentration of heavy metal ions, temperature and contact time, were thoroughly investigated to explore their effect on adsorption capacity of ECSDNH. The obtained results showed that ECSDNH had higher adsorption capacity for Zn2+, Ni2+ and Mn2+. The maximum adsorption capacities of Zn2+, Ni2+ and Mn2+ were 160.19 mg/g, 72.67 mg/g and 52.43 mg/g at 298 K, respectively. The pseudo-second-order kinetic model and Langmuir isotherm model fit the experimental data fairly well. The thermodynamic parameters of the adsorption, ΔH°, ΔS°, and ΔG°, were also calculated. In addition, the ECSDNH still had higher removal efficiency for three metal ions after three adsorption-regeneration cycles, indicating its potential application for removing heavy metal ions from wastewater.

Study on Mechanical and Microscopic Properties of Nickel–Copper-Contaminated Soil Solidified by Cement, Fly Ash and Desulfurization Gypsum Under Carbonization Condition

The engineering characteristics of remediated soil are easily affected by CO2 erosion in nature. However, there are limited investigations on the mechanical and microscopic properties of heavy metal-contaminated soil. This study introduces effect of accelerated carbonization on the mechanical and microscopic properties of nickel–copper-contaminated soil, and the soil has been treated with a novel curing agent, formed by mixing cement, fly ash and desulfurization gypsum (CFG). The objective of the study is to ascertain CO2 erosion resistance of nickel–copper-contaminated soil solidified by CFG. Using unconfined compressive strength (UCS) tests, carbonization depth, X-ray diffraction, and scanning electron microscopy, the sample’s characteristics are investigated under different carbonization times and heavy metal ion concentrations. The results demonstrate that the UCS of samples of Ni0Cu0, Ni0.02, and Ni0.4 decrease with the increasing carbonization time, while that of Ni1, Cu1, and Ni1Cu1 increase initially and then decrease; in addition, when the concentration of heavy metals is lower, the effect of carbonization on UCS of samples is more significant. Moreover, the carbonization depth of samples increases with the increasing carbonization time, and the prediction model is given. Furthermore, the microscopic analysis demonstrates that calcium carbonate is the main carbonization product. The decomposition of hydrated calcium silicate gel leads to poor integrity of the structure and more pores produced in samples, which is the main reason for the decrease of the UCS in the process of carbonization. The outcomes of this investigation provide a reference for the durability in practical engineering of heavy metal-contaminated soil solidified by CFG.

Determination of influence of pH on reaction mixture of ferritation process with electromagnetic pulse activation on the processing of galvanic sludge

This paper considers prospects for increasing the level of environmental safety of industrial enterprises as a result of the implementation of resource-saving technology of processing galvanic sludge using the ferritization method. The effectiveness of the use of electromagnetic pulse discharges for resource-saving activation of the ferritization process with the extraction of heavy metal ions from sludge (Fe, Ni, Cu, Zn) has been confirmed. The influence of key parameters of the process such as the pH value of the reaction mixture and the initial concentrations of metals in the solution on the quality of processing galvanic sludge by ferritization has been experimentally investigated. It was determined that with an increase in the pH value from 8.5 to 10.5 the residual concentrations of metal ions decrease to the values of 0.1÷0.25 mg/dm3 regardless of the total initial concentrations. It has been established that the technique of electromagnetic pulse activation ensures an adequate degree of extraction of metal ions of 99.9 %; it also has indisputable energy advantages compared to the thermal method: energy costs are reduced by more than 60 %. That indicates the suitability of purified water for reuse in galvanic production in terms of the requirements for the content of heavy metal ions in it. In addition, the structural studies of ferritization sediment samples have been carried out. The sediment is characterized by the maximum content of crystalline ferromagnetic phases of ferrite. It was established that an increase in the pH of the initial reaction mixture leads to an increase in the ferrite phase in sedimentation: at pH=10.5, phases were detected, which are characterized by a maximum ferrite content (exceeding 76 %). The proposed resource-saving ferritization process prevents environmental pollution, ensures efficient and rational utilization of raw materials and energy in the industry; it also makes it possible to obtain commodity products from industrial waste.

Heavy metal removal by biomass-derived carbon nanotubes as a greener environmental remediation: A comprehensive review

The concentrations of heavy metal ions found in waterways near industrial zones are often exceed the prescribed limits, posing a continued danger to the environment and public health. Therefore, greater attention has been devoted into finding the efficient solutions for adsorbing heavy metal ions. This review paper focuses on the synthesis of carbon nanotubes (CNTs) from biomass and their application in the removal of heavy metals from aqueous solutions. Techniques to produce CNTs, benefits of modification with various functional groups to enhance sorption uptake, effects of operating parameters, and adsorption mechanisms are reviewed. Adsorption occurs via physical adsorption, electrostatic interaction, surface complexation, and interaction between functional groups and heavy metal ions. Moreover, factors such as pH level, CNTs dosage, duration, temperature, ionic strength, and surface property of adsorbents have been identified as the common factors influencing the adsorption of heavy metals. The oxygenated functional groups initially present on the surface of the modified CNTs are responsible towards the adsorption enhancement of commonly-encountered heavy metals such as Pb2+, Cu2+, Cd2+, Co2+, Zn2+, Ni2+, Hg2+, and Cr6+. Despite the recent advances in the application of CNTs in environmental clean-up and pollution treatment have been demonstrated, major obstacles of CNTs such as high synthesis cost, the agglomeration in the post-treated solutions and the secondary pollution from chemicals in the surface modification, should be critically addressed in the future studies for successful large-scale applications of CNTs.

Environmental photochemistry in Solanum trilobatum mediated plasmonic nanoparticles as a probe for the detection of Cd2+ ions in water

Nowadays world deals with a lot of environmental troubles out of which water pollution is very dangerous. Water gets contaminated by heavy metal ions is a universal problem which needs suitable consideration to keep up the quality of the water. It will be advantageous that an easy device can be detecting the concentration of heavy metal ions in water. Here, a contaminant, cadmium from industrial affluent into water is considered and focused. Gold nanoparticles (AuNPs) have been synthesized by Solanum trilobatum leaf extract and its applications of antifungal and sensing activity was reported here. The influences of different concentration of these reducing agent on the synthesis of AuNPs (G5 and G10) have been evaluated. The structural, optical, vibrational, morphological and compositional properties of the AuNPs were studied through XRD, UV–vis spectra, FTIR, HRTEM and EDAX analysis. The optical studies showed surface plasmon absorbance peak at 526 nm. It shows that the absorbance of the peak becomes narrow with a higher concentration of leaf extract. XRD results showed the average size of the AuNPs was 8 nm. It also confirmed the high crystallinity of nanoparticles. FTIR exposes that amine and carboxyl groups may be involved in the stabilization and reduction mechanism. TEM pictures of both G10 and G5 demonstrate merely spherical nanoparticles. This morphology control is taken place owing to the adsorbed amine and carboxyl groups onto the gold nanoparticles cap the particles and improve the stability. The presence of gold elements in the sample was identified with the help of EDAX. The sensitivity of the system towards various Cd2+ concentrations was measured as 0.058/mM for G5 and 0.095/mM for G10. The prepared nanoparticles produced highest zone of inhibition (ZOI) of 17.5 mm and 19 mm against human being pathogenic fungi Aspergillus Flavus and Candida albicans respectively. Here, small sized spherical nanoparticles showed good antifungal activity.

Potential bioremediation of heavy metal ions, polycyclic aromatic hydrocarbons and biofilms with South African hot spring bacteria

Hot spring bacteria, Bacillus and Bacillus-related spp. from South Africa were screened for biosorption and biosurfactant properties for bioremediation of toxic pollutants. Concentrations of heavy metal ions of copper, chromium, nickel and iron were determined spectrophotometrically. Biosorption resulted in reductions of chromium and copper with four isolates (7T, 9T, 30M, 83Li) but not for iron and nickel. The majority of 40 isolates were biosurfactant positive using paraffin oil. Twelve of which were further screened against petroleum and sunflower seed oil with only four showing positive in all assays tested (16S, 71T, 76S, 85Li). By LC-MS, two isolates (76S, 77S) were shown to produce biosurfactant, subtilisin. Nine biosurfactant-positive isolates were screened for their anti-biofilm properties. Brevibacillus sp. (16S) was able to disrupt a crystal violet stained biofilm of Bacillus subtilis (54T). Screening of bacterial isolates from hot springs reveals potential bacterial candidates with diverse biophysical properties that can be useful in bioremediation of hazardous polluted water.

Copper and Lead Ions Removal by Electrocoagulation: Process Performance and Implications for Energy Consumption

Electroplating wastewater contains high amount of heavy metals that can cause serious problems to humans and the environment. Therefore, it is necessary to remove heavy metals from electroplating wastewater. The aim of this research was to examine the electrocoagulation (EC) process for removing the copper (Cu) and lead (Pb) ions from wastewater using aluminum electrodes. It also analyzes the removal efficiency and energy requirement rate of the EC method for heavy metals removal from wastewater. Regarding this matter, the operational parameters of the EC process were varied, including time (20−40 min), current density (40−80 A/m2), pH (3−11), and initial concentration of heavy metals. The concentration of heavy metals ions was analyzed using the atomic absorption spectroscopy (AAS) method. The results showed that the concentration of lead and copper ions decreased with the increase in EC time. The current density was observed as a notable parameter. High current density has an effect on increasing energy consumption. On the other hand, the performance of the electrocoagulation process decreased at low pH. The higher initial concentration of heavy metals resulted in higher removal efficiency than the lower concentration. The removal efficiency of copper and lead ions was 89.88% and 98.76%, respectively, at 40 min with electrocoagulation treatment of 80 A/m2 current density and pH 9. At this condition, the specific amounts of dissolved electrodes were 0.2201 kg/m3, and the energy consumption was 21.6 kWh/m3. The kinetic study showed that the removal of the ions follows the first-order model.

Indigoidine biosynthesis triggered by the heavy metal-responsive transcription regulator: a visual whole-cell biosensor.

During the last few decades, whole-cell biosensors have attracted increasing attention for their enormous potential in monitoring bioavailable heavy metal contaminations in the ecosystem. Visual and measurable output signals by employing natural pigments have been demonstrated to offer another potential choice to indicate the existence of bioavailable heavy metals in recent years. The biosynthesis of the blue pigment indigoidine has been achieved in E. coli following heterologous expression of both BpsA (a single-module non-ribosomal peptide synthetase) and PcpS (a PPTase to activate apo-BpsA). Moreover, we demonstrated herein the development of the indigoidine-based whole-cell biosensors to detect bioavailable Hg(II) and Pb(II) in water samples by employing metal-responsive transcriptional regulator MerR and PbrR as the sensory elements, and the indigoidine biosynthesis gene cluster as a reporter element. The resulting indigoidine-based biosensors presented a good selectivity and high sensitivity to target metal ions. High concentration of target metal exposure could be clearly recognized by the naked eye due to the color change by the secretion of indigoidine, and quantified by measuring the absorbance of the culture supernatants at 600 nm. Dose-response relationships existed between the exposure concentrations of target heavy metals and the production of indigoidine. Although fairly good linear relationships were obtained in a relatively limited concentration range of the concentrations of heavy metal ions, these findings suggest that genetically controlled indigoidine biosynthesis triggered by the MerR family transcriptional regulator can enable a sensitive, visual, and qualitative whole-cell biosensor for bioindicating the presence of bioaccessible heavy metal in environmental water samples. KEY POINTS: • Biosynthesis pathway of indigoidine reconstructed in a high copy number plasmid in E. coli. • Visual and colorimetric detection of Hg(II) and Pb(II) by manipulation of indigoidine biosynthesis through MerR family metalloregulator. •Enhanced detection sensitivity toward Hg(II) and Pb(II) achieved using novel pigment-based whole-cell biosensors.

Вплив іонів важких металів на екотоксикологічні показники витушки рогової (Mollusca, Gastropoda, Pulmonata, Bulinidae)

The influence of different concentrations of ions of copper, zinc, nickel, manganese of the aquatic environment on the ecotoxicological indicators of the wide range and the most numerous species of malacofauna of Ukraine – Planorbarius corneus (Linnaeus, 1758) was studied. According to the level of toxic effect on the coils, the pollutants studied by us belong to the categories of low-toxic (Mn2+), moderately toxic (Ni2+), highly toxic (Zn2+) and highly toxic (Cu2+) substances. The values of subthreshold, sublethal, chronically lethal, and acute lethal concentrations for each of the used toxicants (mg/dm3) were determined according to the peculiarities of behavior and physiological condition of the experimental animals. As the concentrations of metal ions in the medium increase, the values of the latent period in P. corneus increase. The first signs of poisoning in animals are a weakening of motor activity and increased mucus secretion. At lethal concentrations (LC100) of these toxicants in experimental mollusks develops a rapid pathological process. By the end of the experiment, all individuals in this group die. With increasing concentrations of heavy metal ions, lethal time and lethal mean time decrease. The highest lethal time values were observed for manganese (II) ions, and the lowest for copper ions. The reversibility of mollusk poisoning by different concentrations of these metals was studied. Restoration of functions in the studied animals is carried out in reverse order. Under the action of the same concentrations of heavy metal ions, the duration of the lethal mean time is different. The value of the coefficient of endurance under the influence of heavy metals on the horn extract decreases from high to low concentrations. At subthreshold concentrations, this coefficient cannot be established due to the absence of 100 % death of individuals until the end of the acute experiment. The values of the adaptation coefficient are the highest for highly toxic metal (Cu2+) and the lowest for weakly toxic (Mn2+). Under the action of copper ions, the adaptation of animals to the effects of the toxicant is temporary, followed by depression.

A prediction method of electrocoagulation reactor removal rate based on Long Term and Short Term Memory–Autoregressive Integrated Moving Average Model

In the process of electrochemical wastewater treatment, the removal rate of electrocoagulation reactor will be affected by various factors such as the pH value of wastewater solution, the current density, the wastewater flow rate and the initial concentration of heavy metal ions. Therefore, this study proposes a prediction method of the removal rate of the electrocoagulation reactor based on deep learning Long and Short-Term Memory (LSTM) network combined with the Autoregressive Integrated Moving Average Model (ARIMA) commonly used in engineering. Firstly, according to the concentration of heavy metal ions in the outlet and inlet solution of the reactor, the calculation formula for the removal rate of the reactor is defined. Secondly, in order to deepen the LSTM network model to analyze and learn the change trend of the historical removal rate data, the gradient value of the historical removal rate of the reactor before and after the change is extracted as its change feature value, and this feature value is taken as one of the input variables of the LSTM network model. Comprehensive analysis considered important factors such as the historical removal rate value of the reactor, the initial pH value of the wastewater solution, the voltage and current value, and the wastewater flow rate as the input variables of the LSTM deep learning network. The predicted value of the removal rate of electrocoagulation reactor is concluded by testing the combination of activation function and the number of fully connected layers, and the error compensation of the predicted value is carried out by using the ARIMA model. The effectiveness of the proposed method is verified by the industrial data collected from a wastewater treatment plant.