Contaminated Water Streams Research Articles

Co-Al layered double oxide activated carbon composite for eliminating lead ions from water

In the current study, preparation of cobalt-aluminum layered double oxide doped activated carbon (Co-Al LDO/AC) was achieved by the co-precipitation technique and utilized for the remediation of lead (Pb2+) from water. Various methods were employed to examine the properties of the composite material, including BET, XRD, FTIR, SEM, and EDS analysis. The material characterization outcomes indicated that the LDO structure was successfully incorporated into the AC matrices with a surface area of 189.4 m2/g. The influence of adsorption parameters including Co-Al LDO/AC dosage, period of contact, initial Pb2+ loading, and initial solution pH were investigated. Moreover, the isotherm and kinetic models were investigated to provide a deeper understanding of the elimination mechanism of Pb2+ ions. The adsorption results illustrated that pH has a substantial influence on Pb2+ removal with a highest removal effectiveness at pH = 6 and a fast adsorption rate within 7 h. The kinetic data were well aligned with the pseudo-second-order model while the isotherm data obeyed the Sips model (R2>0.966). The highest adsorption uptake, estimated by the Sips model was 25.09 mg/g. Considering the modeling and characterization of the spent Co-Al LDO/AC, a chemical interaction process was involved in the elimination process and mainly controlled by ion exchange, electrostatic interactions, and surface complexation mechanisms. Accordingly, the Co-Al LDO/AC could have great potential as a promising hybrid for the purification of toxic Pb2+ ions from contaminated water streams.

Effects of Temperature and DC Electric Fields on Perfluorooctanoic Acid Sorption Kinetics to Activated Carbon.

Sorption to activated carbon is a common approach to reducing environmental risks of waterborne perfluorooctanoic acid (PFOA), while effective and flexible approaches to PFOA sorption are needed. Variations in temperature or the use of electrokinetic phenomena (electroosmosis and electromigration) in the presence of external DC electric fields have been shown to alter the contaminant sorption of contaminants. Their role in PFOA sorption, however, remains unclear. Here, we investigated the joint effects of DC electric fields and the temperature on the sorption of PFOA on activated carbon. Temperature-dependent batch and column sorption experiments were performed in the presence and absence of DC fields, and the results were evaluated by using different kinetic sorption models. We found an emerging interplay of DC and temperature on PFOA sorption, which was linked via the liquid viscosity (η) of the electrolyte. For instance, the combined presence of a DC field and low temperature increased the PFOA loading up to 38% in 48 h relative to DC-free controls. We further developed a model that allowed us to predict temperature- and DC field strength-dependent electrokinetic benefits on the drivers of PFOA sorption kinetics (i.e., intraparticle diffusivity and the film mass transfer coefficient). Our insights may give rise to future DC- and temperature-driven applications for PFOA sorption, for instance, in response to fluctuating PFOA concentrations in contaminated water streams.

VERTICAL DISTRIBUTION OF RADIONUCLIDES IN SOILS OF SEMIPALATINSK TEST SITE

The article addresses the pattern of vertical distribution of the major long-lived man-made radionuclides 137Cs, 241Am, 90Sr and 239+240Pu in soils of the Semipalatinsk Test Site. Areas of different contamination with radionuclides are discussed – places of aboveground nuclear and fusion tests conducted at the ‘Experimental Field’ site, the fallout in the form of plumes within the Semipalatinsk Test Site, areas of radiological warfare agent tests at the ‘4А’ site, areas of meadow ecosystems associated with radioactively contaminated water streams from test adits of the ‘Degelen’ testing site, conventionally ‘background’ areas of the test site, in which no nuclear or fusion tests were conducted. In the course of research, differences were revealed in the vertical distribution of radionuclides of interest in soils of the above areas. Differences are attributed to the pattern of how contamination with radionuclides is formed and to abiotic and biotic factors such as physical and chemical soil properties, moistening conditions, human activity and others. Based upon findings, recommendations were developed, aimed at the optimization of research into the vertical distribution of radionuclides in the soil cover of the former Semipalatinsk test Site. In particular, it was found that when undertaking such research, it was sufficient to confine oneself to dividing a territory by the soil type and restrict the research depth to 30 cm.

Designing engineered biopolymer mesh filter for robust sequestration of chromium (VI), fluoride and other emerging pollutants: A sustainable approach

In this study, we demonstrate the use of functionalized inter-penetrated biomaterial mesh composites (FMCs) as rapid hazardous heavy metal and emerging pollutant retention media. Varying composition of metal precursors, the biopolymers were first functionalized to be converted into highly active hazard retention sites. Further, the structural and morphological confirmation of these synthesized FMC’s were characterized using different analytical tools such as FT-IR, p-XRD, FE-SEM, XPS, DLS, and Zeta potential. Likewise, experiments were conducted to investigate the removal efficiency of toxic pollutants such Cr6+, F−, and series of emerging pollutants. The optimized composition among the five variant FMCs showed maximum adsorption capacity of 315.86 mg/g for Cr6+ ions, 52.75 mg/g for fluoride ions, 77.71 mg/g for Ciploflaxin and 61.5 mg/g for Diclofenac. Further, to investigate the practical use and robustness of the composite materials, continuous flow adsorptive membrane filters were fabricated and then the adsorptive membrane was tested in continuous filtration mode for the robust removal of series of pollutants both in simulated feed condition as well as real contaminated samples. In this mode, the adsorptive membrane showed a flux of ∼ 300–900 LMH and > 98% retention efficiency for Cr6+, 92% rejection for CTAB, and 60% retention for both low molecular weight pharmaceutical pollutants and F− ions. Therefore, this research demonstrates a sustainable strategy for efficiently removing Cr6+, F−, and emerging pollutants like active pharmaceutical ingredients (APIs) from contaminated water streams.

Comparative adsorption of Eriochrome black T onto recyclable steel dust wastes: Isotherm, kinetics and thermodynamic studies

In this study, low-cost steel dust wastes from two different steel-manufacturing plants were investigated for the decontamination of water containing an anionic dye, Eriochrome black T (EBT). The characterization results indicated that the steel dust particles are mesoporous material with heterogenous structure and exhibit different surface functionalities that, mainly, included metal oxides and C-O groups. The steel dust particles showed high affinity towards EBT dye (100% removal) at pH 2, and dye concentration 20 mg/L. The kinetic data was better described by pseudo-second order model indicating chemisorption interactions. The isotherm results showed good fitting to the Langmuir isotherm model implying monolayer EBT adsorption onto steel dust particles. The maximum adsorption capacity of Q-Steel and L-Steel was 100.20 mg/g and 94.18 mg/g, respectively. The thermodynamic study demonstrated endothermic nature of EBT adsorption process. The steel dust particles showed excellent removal performance of EBT dye (i.e., less than 10% reduction) after five regeneration cycles. This demonstrated that steel dust particles can be directly, used as potential low cost and recyclable adsorbent material for treating dye contaminated water streams.

Sustainable green nanoadsorbents for remediation of pharmaceuticals from water and wastewater: A critical review

In the last three decades, pharmaceutical research has increased tremendously to offer safe and healthy life. However, the high consumption of these harmful drugs has risen devastating impact on ecosystems. Therefore, it is worldwide paramount concern to effectively clean pharmaceuticals contaminated water streams to ensure safer environment and healthier life. Nanotechnology enables to produce new, high-technical material, such as membranes, adsorbent, nano-catalysts, functional surfaces, coverages and reagents for more effective water and wastewater cleanup processes. Nevertheless, nano-sorbent materials are regarded the most appropriate treatment technology for water and wastewater because of their facile application and a large number of adsorbents. Several conventional techniques have been operational for domestic wastewater treatment but are inefficient for pharmaceuticals removal. Alternatively, adsorption techniques have played a pivotal role in water and wastewater treatment for a long, but their rise in attraction is proportional with the continuous emergence of new micropollutants in the aquatic environment and new discoveries of sustainable and low-cost adsorbents. Recently, advancements in adsorption technique for wastewater treatment through nanoadsorbents has greatly increased due to its low production cost, sustainability, better physicochemical properties and high removal performance for pharmaceuticals. Herein, this review critically evaluates the performance of sustainable green nanoadsorbent for the remediation of pharmaceutical pollutants from water. The influential sorption parameters and interaction mechanism are also discussed. Moreover, the future prospects of nanoadsorbents for the remediation of pharmaceuticals are also presented.

Fixed-bed flow experiments with supported green nZVI for the remediation of contaminated waters: Effect of pH and background solution composition

Aim of this study is to evaluate the performance of a nanocomposite material (R-nFe), consisting of nano zero valent iron (nZVI) and a cation exchange resin, for Cr(VI) reduction and heavy metals removal from contaminated water streams. The effect of pH and the background solution composition was investigated by conducting three columns tests. In Column I, the experiments were carried out using NaCl as background electrolyte while in Column II and III the background solution consisted of 50% tertiary effluents of a waste water treatment plant and 50% deionized water. The kinetics of Cr(VI) removal was found to be much faster at acidic pHs. Based on the experimental results it was calculated that the required contact time of the permeating solution with the RnFe beads for Cr(VI) removal at pH 7 is 6.5 times longer than at pH 4. The results also revealed the role of competing ions on the performance of RnFe. During the operation of the column with an inert electrolyte, such as NaCl, the RnFe bed removed an amount of Cr(VI) equivalent to 4200 mg/kg. When the column was fed with a water stream containing relatively high levels of nitrates, the RnFe removed efficiently only 190 mg/kg Cr(VI), due to the competitive consumption of nanoiron for the reduction of nitrates. The nanocomposite was found to be very efficient for the simultaneous removal of tested heavy metals, i.e. Cu, Zn, Ni, Cd and Pb, which were selectively retained in the cation exchange sites of the supporting resin matrix.

Electrochemical Destruction of ‘Forever Chemicals’: The Right Solution at the Right Time

Per- and polyfluoroalkyl substances (PFAS) are manmade compounds used in a variety of industrial applications, and their consumption by humans can lead to many adverse health effects. Due to their high stability, destroying PFAS once they have contaminated water streams has become a major challenge. One promising remediation method is electrochemical oxidation (EO). To perform EO, electrode materials that can withstand high current and voltage conditions are required. Boron-doped diamond (BDD) is one such material, and its viability has been demonstrated for the EO of PFAS in a custom water treatment system applied and optimized to high-strength waste streams laden with PFAS. The permanent and disruptive nature of the technology lends itself to applicability in complex media such as IX regenerates, RO rejects, aqueous film forming foam (AFFF), industrial wastewaters, and landfill leachates, among others.

Synthesis of a zinc–imidazole metal–organic framework (ZIF-8) using ZnO rods grown on cotton fabrics as precursors: arsenate absorption studies

A Zn-imidazolate metal–organic framework, ZIF-8, was synthesized using ZnO nanorods grown on cotton fibers as precursors. We monitored the synthesis path via X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The fibers were evaluated by their capacity to absorb arsenate from aqueous solutions and we used scanning transmission electron microscopy–high angle annular dark-field (STEM–HAADF) imaging to observe the transport gradient of arsenate across the ZIF layer and the ZnO interface. The uptake of arsenate in the fibers coated with ZIF-8 on top of the ZnO rods, at pH 7, was of 70% while the uptake of the fibers coated only with ZnO rods was 38%. In addition to the enhanced uptake capacity, the fibers containing ZIF-8 also exhibited lower amounts of Zn leaching into the arsenate solutions. These results provide insights on the synthesis of Zn-imidazole metal–organic frameworks and confirm the potential use of ZIF-8 in the removal of arsenate from contaminated water streams.

Electrokinetic effects on the interaction of phenanthrene with geo-sorbents.

Interactions with solid matrices control the persistence and (bio-)degradability of hydrophobic organic chemicals (HOC). Approaches influencing the rate or extent of HOC interactions with matrices are thus longed for. When a direct current (DC) electric field is applied to a matrix immersed in an ionic solution, it invokes transport processes including electromigration, electrophoresis, and electroosmotic flow (EOF). EOF is the surface charge-induced movement of pore fluids. It has the potential to mobilize uncharged organic contaminants and, hence, to influence their interactions with sorbing geo-matrices (i.e. geo-sorbents). Here, we assessed the effects of weak DC electric fields on sorption and desorption of phenanthrene (PHE) in various mineral and carbonaceous geo-sorbents. We found that DC fields significantly changed the rates and extent of PHE sorption and desorption as compared to DC-free controls. A distinct correlation between the Gibbs free energy change (ΔG°) and electrokinetic effects such as the EOF velocity was observed; in case of mineral sorbents EOF limited (or even inhibited) PHE sorption and increased its desorption. In strongly sorbing carbonaceous geo-sorbents, however, EOF significantly increased the rates of PHE sorption and reduced PHE desorption by > 99% for both activated charcoal and exfoliated graphite. Based on our findings, an approach linking ΔG° and EOF velocity was developed to estimate DC-induced PHE sorption and desorption benefits on mineral and carbonaceous sorbents. We conclude that such kinetic regulation gives rise to future technical applications that may allow modulating sorption processes e.g. in response to fluctuating sorbate concentrations in contaminated water streams.

Selective and Efficient Removal of Fluoride from Water: In Situ Engineered Amyloid Fibril/ZrO2 Hybrid Membranes.

We report a new strategy for efficient removal of F- from contaminated water streams, and it relies on carbon hybrid membranes made of amyloid fibril/ZrO2 nanoparticles (<10 nm). These membranes exhibit superior selectivity for F- against various competitive ions, with a distribution coefficient (Kd ) as high as 6820 mL g-1 , exceeding commercial ion-exchange resins (IRA-900) by 180 times and outdoing the performance of most commercial carbon-activated aluminum membranes. At both low and high (ca. 200 mg L-1 ) F- concentrations, the membrane efficiency exceeds 99.5 % removal. For real untreated municipal tap water (ca. 2.8 mg L-1 ) under continuous operating mode, data indicates that about 1750 kg water m-2 membrane can be treated while maintaining drinking water quality, and the saturated membranes can be regenerated and reused several times without decrease in performance. This technology is promising for mitigating the problem of fluoride water contamination worldwide.

Selective and Efficient Removal of Fluoride from Water: In Situ Engineered Amyloid Fibril/ZrO2 Hybrid Membranes

AbstractWe report a new strategy for efficient removal of F− from contaminated water streams, and it relies on carbon hybrid membranes made of amyloid fibril/ZrO2 nanoparticles (&lt;10 nm). These membranes exhibit superior selectivity for F− against various competitive ions, with a distribution coefficient (Kd) as high as 6820 mL g−1, exceeding commercial ion‐exchange resins (IRA‐900) by 180 times and outdoing the performance of most commercial carbon‐activated aluminum membranes. At both low and high (ca. 200 mg L−1) F− concentrations, the membrane efficiency exceeds 99.5 % removal. For real untreated municipal tap water (ca. 2.8 mg L−1) under continuous operating mode, data indicates that about 1750 kg water m−2 membrane can be treated while maintaining drinking water quality, and the saturated membranes can be regenerated and reused several times without decrease in performance. This technology is promising for mitigating the problem of fluoride water contamination worldwide.

Engineering and kinetic aspects of bacterial uranium reduction for the remediation of uranium contaminated environments.

Biological reduction of soluble uranium from U(VI) to insoluble U(IV) coupled to the oxidation of an electron donor (hydrogen or organic compounds) is a potentially cost-efficient way to reduce the U concentrations in contaminated waters to below regulatory limits. A variety of microorganisms originating from both U contaminated and non-contaminated environments have demonstrated U(VI) reduction capacity under anaerobic conditions. Bioreduction of U(VI) is considered especially promising for in situ remediation, where the activity of indigenous microorganisms is stimulated by supplying a suitable electron donor to the subsurface to contain U contamination to a specific location in a sparingly soluble form. Less studied microbial biofilm-based bioreactors and bioelectrochemical systems have also shown potential for efficient U(VI) reduction to remove U from contaminated water streams. This review compares the advantages and challenges of U(VI)-reducing in situ remediation processes, bioreactors and bioelectrochemical systems. In addition, the current knowledge of U(VI) bioreduction mechanisms and factors affecting U(VI) reduction kinetics (e.g. pH, temperature, and the chemical composition of the contaminated water) are discussed, as both of these aspects are important in designing efficient remediation processes.

Utilization of montmorillonite as a refining solution for the treatment of ametryn, a second generation of pesticide

This study reported the feasibility of natural montmorillonite as a refining solution for the adsorptive treatment of ametryn pesticide. The adsorption performance was evaluate with respect to the initial concentrations, contact time and solution pH. Equilibrium data were simulated using the nonlinear Langmuir, Freundlich and Temkin isotherm models, and kinetic equations. The physical and chemical properties were examined using the Scanning Electron Microscopy (SEM), Fourier-Transform Infrared (FTIR) Spectroscopy, nitrogen adsorption-desorption curve, and zero-point-of-charge. Results showed that the equilibrium data were well fitted to the Langmuir isotherm model and pseudo-second order kinetic equation, with a monolayer adsorption capacity of 188.81mg/g. The natural montmorillonite illustrated the high Brunaeur–Emmet–Teller (BET) surface area and total pore volume of 164.79m2/g and 0.271cm3/g, respectively, with a pore diameter of 65.74Å. Thermodynamic study demonstrated that the adsorption process was spontaneous and endothermic in nature. The findings revealed the potential of montmorillonite as an outstanding and viable source of natural adsorbent for the successive uptake of ametryn from the contaminated water streams.

Removal of Iopromide and Its Intermediates from Ozone-Treated Water Using Granular Activated Carbon

The potential of granular activated carbon (GAC) to remove iopromide and its intermediates from ozone-treated river water was evaluated. Mass spectrum analysis showed that ozone treatment lead to partial removal of iopromide (m/z 791.8) with generation of various intermediates. GAC demonstrated a lower iopromide adsorption (1.60 μg/g) in the presence of natural organic matter (NOM) compared to NOM-free water (12.54 μg/g), indicating the inhibitory effect of NOM on iopromide adsorption. Ozone treatment of the influent reduced the inhibitory effect of NOM by altering its composition and inducing polarity shift. GAC post-treatment resulted in improved removal of residual iopromide and its intermediates from the ozone-treated influent. Application of such combined treatment of ozonation followed by GAC adsorption can be an effective strategy for the removal of iopromide and its intermediates from contaminated water streams.

Removal of arsenate and arsenite from aqueous solution by adsorption on clay minerals

Sorption of arsenic species [As(V) and As(III)] on different clay minerals including kaolinite (KGa-1), montmorillonite (SWy-1), and nontronites (NAU-1 and NAU-2) with respect to sorption kinetics, isotherms and pH was investigated. As(V) and As(III) sorption on clay minerals was significantly influenced by pH. Higher sorption of As(V) was observed at low pH that decreased above pH 5.0, while As(III) sorption was maximum around pH 7.0. The sorption kinetics was well described by the pseudo-second-order equation for both As(V) and As(III). Among the tested clay minerals, NAU-2 was most effective for the removal of arsenic with rate constants of 0.084 and 0.056 g mg− 1 min− 1 for As(V) and As(III), respectively. A good correlation was observed between adsorbing capacity (qe) and equilibrium mass concentration (Ce) using the isothermal Freundlich adsorption model for SWy-1, NAU-1, and NAU-2 minerals as indicated by the high values of R2 coefficient. Our results indicate that clay minerals can serve as effective sorbents for the removal of As from contaminated water streams.

STUDIES ON GLUTARALDEHYDE CROSSLINKED XANTHATED CHITOSAN TOWARDS THE REMOVAL OF MERCURY (II) FROM CONTAMINATED WATER STREAMS

Chitosan was cross linked with gluteraldehyde and chemically modified by introducing xanthate group onto its backbone using carbon disulfide under alkaline conditions. This crosslinked xanthated chitosan flakes (XC) was used as an adsorbent for the removal of mercury ions from contaminated water streams near the coal mines. XC was found to be far more efficient than the conventionally used adsorbent activated carbon. FTIR studies indicated the interaction both amine and the xanthate groups. The maximum uptake of mercury by XC in batch studies was found to be 425.5 2.5 mg/g at an optimum pH of 4.0. Due to the high formation constant of mercury with xanthate and adsorption was carried out at pH 4, anions like nitrate, chloride and sulfate up to 0.5M did not interfere in the adsorption behavior of mercury. Thermodynamic parameters such as .S, .H and .G indicated the suitability of XC towards the removal of mercury. Desorption of the bound mercury from XC was accomplished with 0.01 M NaOH. The data from regeneration efficiencies for five cycles, evidenced the reusability of XC in the treatment of mercury-laden wastewater.

Thiol functionalized sugarcane bagasse—A low cost adsorbent for mercury remediation from compact fluorescent bulbs and contaminated water streams

Novel thiol functionalized sugarcane bagasse (SCB-S) was synthesized and structurally characterized by various techniques like scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) and Fourier transform infra red (FTIR) spectroscopy. The adsorption properties of Hg2+ as a function of pH, contact time and initial metal concentration were characterized by cold vapor AAS. The adsorption kinetics fitted the pseudo second order kinetics and equilibrium reached within 120min. The experimental data were modeled with Langmuir and Freundlich isotherms and various isotherm parameters were evaluated. Thermodynamic parameters such as ΔS, ΔH and ΔG indicated the suitability of SCB-S for the removal of Hg(II). Recycling studies indicated the performance of SCB-S up to five cycles without appreciable depreciation in the capacity. Studies have been conducted to demonstrate the applicability of the sorbent toward the removal of Hg(0) vapor from broken compact fluorescent light (CFL) bulbs at ambient temperature and Hg(II) from contaminated water streams.

Silver-modified clinoptilolite for the removal of Escherichia coli and heavy metals from aqueous solutions.

This paper investigates the potential of using the silver antibacterial properties combined with the metal ion exchange characteristics of silver-modified clinoptilolite to produce a treatment system capable of removing both contaminants from aqueous streams. The results have shown that silver-modified clinoptilolite is capable of completely eliminating Escherichia coli after 30-min contact time demonstrating its effectiveness as a disinfectant. Systems containing both E. coli and metals exhibited 100 % E. coli reduction after 15-min contact time and maximum metal adsorption removal efficiencies of 97, 98, and 99 % for Pb(2+), Cd(2+), and Zn(2+) respectively after 60 min; 0.182-0.266 mg/g of metal ions were adsorbed by the zeolites in the single- and mixed-metal-containing solutions. Nonmodified clinoptilolite showed no antibacterial properties. This study demonstrated that silver-modified clinoptilolite exhibited high disinfection and heavy metal removal efficiencies and consequently could provide an effective combined treatment system for the removal of E. coli and metals from contaminated water streams.

Enhanced sorption of mercury from compact fluorescent bulbs and contaminated water streams using functionalized multiwalled carbon nanotubes

Three different functionalized multiwalled carbon nanotubes were prepared, namely, oxidized CNTs (CNT-OX), iodide incorporated MWCNT (CNT-I) and sulfur incorporated MWCNT (CNT-S). The as prepared adsorbents were structurally characterized by various spectral techniques like scanning electron microscopy (SEM), energy dispersive X-ray (EDAX), Brunauer, Emmett, and Teller (BET) surface area analyzer, Fourier transform infra red (FTIR) and Raman spectroscopy. Loading of iodide and sulfur was evident from the EDAX graphs. The adsorption properties of Hg2+ as a function of pH, contact time and initial metal concentration were characterized by Cold vapor AAS. The adsorption kinetics fitted the Pseudo second order kinetics and equilibrium was reached within 90min. The experimental data were modeled with Langmuir, Freundlich, Dubinin-Redushkevich and Temkin isotherms and various isotherm parameters were evaluated. It was found that the mercury adsorption capacity for the prepared adsorbents were in the order of CNT-S>CNT-I>CNT-OX>CNT. Studies have been conducted to demonstrate the applicability of the sorbent toward the removal of Hg(0) from broken compact fluorescent light (CFL) bulbs and Hg(II) from contaminated water streams.