Effect Of Ionic Strength Research Articles

The Binding Properties of Antibodies to Z-DNA in the Sera of Normal Healthy Subjects.

Antibodies to DNA are a diverse set of antibodies that bind sites on DNA, a polymeric macromolecule that displays various conformations. In a previous study, we showed that sera of normal healthy subjects (NHS) contain IgG antibodies to Z-DNA, a left-handed helix with a zig-zig backbone. Recent studies have demonstrated the presence of Z-DNA in bacterial biofilms, suggesting a source of this conformation to induce responses. To characterize further antibodies to Z-DNA, we used an ELISA assay with brominated poly(dGdC) as a source of Z-DNA and determined the isotype of these antibodies and their binding properties. Results of these studies indicate that NHS sera contain IgM and IgA as well as IgG anti-Z-DNA antibodies. As shown by the effects of ionic strength in association and dissociation assays, the anti-Z-DNA antibodies bind primarily by electrostatic interactions; this type of binding differs from that of induced anti-Z-DNA antibodies from immunized animals which bind by non-ionic interactions. Furthermore, urea caused dissociation of NHS anti-Z-DNA at molar concentrations much lower than those for the induced antibodies. These studies also showed IgA anti-Z-DNA antibodies in fecal water. Together, these studies demonstrate that antibodies to Z-DNA occur commonly in normal immunity and may arise as a response to Z-DNA of bacterial origin.

Ionic strength alters crosslinker-driven self-organization of microtubules.

The microtubule cytoskeleton is a major structural element inside cells that directs self-organization using microtubule-associated proteins and motors. It has been shown that finite-sized, spindle-like microtubule organizations, called "tactoids," can form in vitro spontaneously from mixtures of tubulin and the antiparallel crosslinker, MAP65, from the MAP65/PRC1/Ase family. Here, we probe the ability of MAP65 to form tactoids as a function of the ionic strength of the buffer to attempt to break the electrostatic interactions binding MAP65 to microtubules and inter-MAP65 binding. We observe that, with increasing monovalent salts, the organizations change from finite tactoids to unbounded length bundles, yet the MAP65 binding and crosslinking appear to stay intact. We further explore the effects of ionic strength on the dissociation constant of MAP65 using both microtubule pelleting and single-molecule binding assays. We find that salt can reduce the binding, yet salt never negates it. Instead, we believe that the salt is affecting the ability of the MAP65 to form phase-separated droplets, which cause the nucleation and growth of tactoids, as recently demonstrated.

Applicability and characterization of the natural Moroccan clay for cationic dye removal: Kinetic, isotherms studies, and application on effluent treatment for textile dyeing

The aim of this study was to investigate the adsorption of methylene blue (MB) using Natural Moroccan clay (NMC). The NMC was characterized by, Brunauer-Emmett-Teller (BET), Point of Zero Charge (pHPZC), Fourier-Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). Adsorption key variables, including dosage of adsorbent dose, solution pH, and initial concentrations, effect of ionic strength, contact time and temperature were inspected for determining their impacts on MB dye removal. The adsorption process of MB onto NMC was examined using various isotherm models, such as Langmuir, Temkin and Freundlich. The results indicate that the adsorption process is characterized by the Langmuir isotherm, which is confirmed by the fitting data and the comparison of the correlation coefficient (R2). This suggests the highest adsorption capacity of 32.14 mg/g. The pseudo-second order kinetic model provides a good fit for the kinetic data, achieving an R2 value of 0.997. From these results, the method is employed for textile wastewater treatment primarily composed of methylene blue.

Modulation of molecular state and air-water interface adsorption behavior of ovalbumin via interference with its surrounding charge distribution

Herein, pH combined with ionic strength was employed to modulate the charge distribution around ovalbumin molecules, and the whole process (from the water phase to the interface) of film formation and stabilization of ovalbumin at the air-water interface was further analyzed. As the pH continuously rose above the isoelectric point, the molecular surface charge increased. More cations, however, reduced the surface charge through the electrostatic shielding effect. The pH and cationic strength were shown to have a remarkable effect on the aggregate size. Intrinsic fluorescence and excitation emission matrix spectroscopy indicated that the migration of tryptophan and tyrosine was accompanied by a change in the backbone structure and rearrangement of the hydrophilic/hydrophobic side chains. Interfacial adsorption kinetic analysis revealed that low pH and ionic strength generally favored the adsorption and stabilization of ovalbumin. Lissajous plots confirmed that stronger intra-interfacial interactions and viscoelastic-like solid interfaces would be generated under the above conditions. Interfacial dilatational rheology analysis illustrated that in most cases, the interfacial film formed by ovalbumin was dominated by an elastic response and produced a nonlinear viscoelastic response under strain. Overall, the combined effect of low pH (pH 5.0) and ionic strength (25 mmol/L and 50 mmol/L) on the surface charge resulted in superior foam capacity (60.00% for pH 5.0 and 50 mmol/L) and stability (97.87% for pH 5.0 and 25 mmol/L). This study detailed the mechanism by which charge influenced the molecular and interfacial properties of ovalbumin, leading the way for the development of protein-based foam systems.

Effect of Ionic Strength and pH on the Sorption of Heavy Metals onto Polyaniline Copolymers in Aqueous Solutions.

Polyaniline (PANI) and two copolymers, poly(aniline-co-o-toluidine) (PoTOL-50) and poly(aniline-co-o-anisidine) (PoANI-50) were synthesized with equal input ratios (1:1) to enhance PANI as sensing material for the sensing of various heavy metal analytes in aqueous solutions. The polymers were evaluated for both their sensitivity and selectivity toward four heavy metals (Ba2+, Cd2+, Cu2+, and Ni2+) and two common matrix interferents (Ca2+ and Mg2+) at 10 and 40 ppm. The effect of pH and ionic strength of the aqueous solutions on the sensitivity and selectivity was also evaluated. All three polymers showed high sensitivity and selectivity to Ba2+. Varying the pH and ionic strength of solutions did not show significant differences in either the selectivity or the sensitivity of the polymers.

Cholesteric Tactoids with Tunable Helical Pitch Assembled by Lysozyme Amyloid Fibrils.

Amyloid fibrils are biological rod-like particles showing liquid-liquid crystalline phase separation into cholesteric phases through a complex behavior of nucleation, growth, and order-order transitions. Yet, controlling the self-assembly of amyloids into liquid crystals, and particularly the resulting helical periodicity, remains challenging. Here, a novel cholesteric system is introduced and characterized based on hen egg white lysozyme (HEWL) amyloid fibrils and the results rationalized via a combination of experiments and theoretical scaling arguments. Specifically, the transition behaviors are elucidated from homogenous nematic, bipolar nematic to cholesteric tactoids following the classic Onsager model and the free energy functional model from Frank-Oseen elasticity theory. Additionally, the critical effects of pH and ionic strength on these order-order-transitions, as well as on the shape and helical pitch of the cholesteric tactoids are demonstrated. It is found that a small increase in pH from 2.0 to 2.8 results in a 34% decrease in pitch, while, on the contrary, increasing ionic strength from 0 to 10mm leads to a 39% increase in pitch. The present study provides an approach to obtain controllable chiral nematic structures from HEWL amyloid fibrils, and may contribute further to the application of protein-based liquid crystals in pitch-sensitive biosensors or biomimetic architectures.

Performance of Anion Exchange Membrane Water Electrolysis with High Ionic Strength Electrolyte

Anion exchange membrane water electrolysis (AEMWE) provides the advantages of conventional alkaline water electrolysis and proton exchange membrane water electrolysis for low-temperature hydrogen production. This study investigates the effect of ionic strength in low hydroxide concentration anolyte on AEMWE performance. The anolyte was recirculated at the anode, and the cathode was operated dry. Different alkali cations in the high ionic strength anolyte improved the cathode overpotential by increasing the water transport from the anode to the cathode. Li+, Na+, K+, and Cs+ cations were tested with K+ providing the lowest electrolysis overpotential among the cations tested. The transference number of the alkali cations was measured by a modified Bruce-Vincent method using a membrane electrode assembly, composed of a hydrogen-evolving cathode and oxygen-evolving anode and anion exchange polymer membrane. The result shows that the cathode overpotential is influenced by the cation mobility, which is related to the hydration shell width. The electrolysis overpotential trend with different alkali cations in the anolyte scaled with the alkali dynamic ionic radius. Durable electrolysis was performed in 1,000 h test at 60 °C and 1 A cm−2.

Collision-attachment simulation of membrane fouling by oppositely and similarly charged colloids

The fouling propensity of oppositely charged colloids (OCC) and similarly charged colloids (SCC) on reverse osmosis (RO) and nanofiltration (NF) membranes are systematically investigated using a developed collision-attachment approach. The probability of successful colloidal attachment (i.e., attachment efficiency) is modelled by Boltzmann energy distribution, which captures the critical roles of colloid-colloid/membrane interaction and permeate drag. Our simulations highlight the important effects of ionic strength Is, colloidal size dp and initial flux J0 on combined fouling. In a moderate condition (e.g., Is =10 mM, dp=50 nm and J0= 100 L/m2h), OCC mixtures shows more severe fouling compared to the respective single foulant owing to electrostatic neutralization. In contrast, the flux loss of SCC species falls between those of the two single foulants but more closely resembles that of the single low-charged colloids due to its weak electrostatic repulsion. Increased ionic strength Is leads to less severe fouling for OCC but more severe fouling for SCC, as a result of the suppressed electrostatic attraction/repulsion. At a high Is (e.g., 3–5 M), all the single and mixed systems show the identical pseudo-stable flux Js. Small colloidal size leads to the drag-controlled condition, where severe fouling occurs for both single and mixed foulants. On the contrary, better flux stability appears at greater dp for both individual and mixed species, thanks to the increasingly dominated role of energy barrier and thus lowered attachment efficiency. Furthermore, higher J0 above limiting flux exerts greater permeate drag, leading to elevated attachment efficiency, and thus more flux losses for both OCC and SCC. Our modelling gains deep insights into the role of energy barrier, permeate drag, and attachment efficiency in governing combined fouling, which provides crucial guidelines for fouling reduction in practical engineering.

The Effect of Ionic Strength on the Formation and Stability of Ovalbumin-Xanthan Gum Complex Emulsions.

Protein-polysaccharide complexes have been widely used to stabilize emulsions, but the effect of NaCl on ovalbumin-xanthan gum (OVA-XG) complex emulsions is unclear. Therefore, OVA-XG complex emulsions with different XG concentrations at pH 5.5 were prepared, and the effects of NaCl on them were explored. The results indicated that the NaCl significantly affected the interaction force between OVA-XG complexes. The NaCl improved the adsorption of proteins at the oil-water interface and significantly enhanced emulsion stability, and the droplet size and zeta potential of the emulsion gradually decreased with increasing NaCl concentrations (0-0.08 M). In particular, 0.08 M NaCl was added to the OVA-0.2% XG emulsion, which had a minimum droplet size of 18.3 μm. Additionally, XG as a stabilizer could improve the stability of the emulsions, and the OVA-0.3% XG emulsion also exhibited good stability, even without NaCl. This study further revealed the effects of NaCl on emulsions, which has positive implications for the application of egg white proteins in food processing.

Functional Properties of Moringa Oleifera Protein Isolates as Influenced by Different Isolation Techniques, pH, and Ionic Strength

AbstractPlant-based proteins are increasingly being utilized as they are sustainable, economical, and can enhance the organoleptic properties of food products. This study investigated the effect of extraction and isolation techniques (alkaline extraction & isoelectric precipitation and salt extraction & micellization) on the functional properties ((solubility, water holding and oil absorption capacity (WHC/OAC), emulsifying activity and stability index (EAI/ESI), foaming capacity and stability (FC/FS), and gelation)) of Moringa oleifera protein isolates. The effect of ionic strength (0.2–1.0 M NaCl) and pH (2–10) on the functional properties were also investigated. Salt extraction & micellization produced an isolate with a high solubility at 0.8 M NaCl and pH 10 (98.1%, 91.8%), EAI at 0.6 M NaCl and pH 6 (56.2 m2/g, 77.0 m2/g), and ESI at 0.8 M NaCl and pH 4 (64.4 min, 243.5 min). Alkaline extraction & isoelectric precipitation resulted in an isolate with a high WHC at 0.6 M NaCl and pH 10 (5.8 g/g, 4.0 g/g), OAC (4.9 g/g), FC at 0.4 M NaCl and pH 2 (203.3%, 163.3%), and gelation at 0.2 M NaCl, 0.4 M NaCl, and pH 8 (20.0%). Both extraction methods can be applied in the valorization of M. oleifera seedcake. Micellized isolate could be used in food emulsions due to better emulsifying properties, while isoelectric isolate can be applied in meats and sauces, owing to better water holding and oil absorption capacity. M. oleifera protein isolates are promising plant-based proteins that can be used in food formulations or to replace animal-derived proteins in food.

Facilitated transport of toluene and naphthalene with humic acid in high- and low-permeability systems: Role of ionic strength and cationic type

The occurrence of colloids on pollutants transport in groundwater has attracted more attention. However, the research on the regulation mechanism of colloids on combined pollutants transport in heterogeneous aquifers is limited. In this study, a series of tank experiments were conducted to systematically investigate the effects of ionic strength, and cation type on humic acid (HA) facilitated transport of toluene (TOL), and naphthalene (NAP) in high- and low-permeability systems. The results showed that HA facilitated pollutants transport in low Na+ solution. In Ca2+ solution, the presence of HA hindered pollutants transport, and the inhibition increased with the increase of ionic strength. Both in Na+ solution and low Ca2+ solution, the influence of heterogeneous structure on pollutant transport played a dominant role, and TOL and NAP had a greater transport potential in the high permeability zone (HPZ) due to the preferential flow. Whereas, deposition of HA aggregates, and electrostatic attractive interaction had negative effects on transport than groundwater flow in high Ca2+ solution. Pollutants were prone to accumulate at the bottom of the HPZ, and the top of the low permeability zone (LPZ). These new findings provide insights into the mechanism of colloids influence on the pollutants transport in heterogenous aquifer.

Evaluation of novel chromatographic prototypes for supercoiled plasmid DNA polishing.

Since the world first approved gene therapeutics, nucleic acid-based therapies have gained prominence. Several strategies for DNA-based therapy have been approved, and numerous clinical trials for plasmid DNA (pDNA)-based vaccines are currently in development. Due to the rising interest in pDNA for vaccination and gene therapy, plasmid manufacturing must become more effective. One of the most critical steps is downstream processing, involving isolation and purification procedures. To comply with the regulatory guidelines, pDNA must be available as a highly purified, homogeneous preparation of supercoiled pDNA (sc pDNA). This process undertakes several challenges, primarily due to the diversity of molecules derived from the producer organism. In this study, different resins were tested for the adsorption and selective polishing of sc pDNA. To identify optimal pDNA adsorption conditions, batch and column assays were performed with different resins while promoting electrostatic and hydrophobic interactions. The effect of ionic strength, pH, and contact time were evaluated and optimized. Additionally, static and dynamic binding capacities were determined for the selected resins. Analytical chromatography and agarose gel electrophoresis were used to assess the selectivity of the most promising resins toward sc pDNA isoform. Also, genomic DNA, endotoxins, and proteins were quantified to characterize the final sc pDNA quality. At the same time, the recovery and purity yields were evaluated by quantification of sc pDNA after the purification procedure. Overall, the results of the chromatographic assays using agmatine- and arginine-based resins have shown promising potential for sc pDNA polishing. Both resins demonstrated excellent binding capacity for pDNA, with agmatine outperforming arginine-based resin in terms of capacity. However, arginine-based resin exhibited a superior pDNA recovery yield, reaching a notable 52.2% recovery compared to 10.09% from agmatine. Furthermore, both resins exhibited high relative purity levels above 90% for the sc pDNA. The comprehensive characterization of the recovered sc pDNA also revealed a significant reduction in gDNA levels, reinforcing the potential of these prototypes for obtaining high-quality and pure sc pDNA. These findings highlight the promising applications of both resins in scalable pDNA purification processes for gene therapy and biopharmaceutical applications.

Application of Musa acuminata mediated iron oxide nanoparticles in the removal of sunset yellow dye

This study deals with the biogenic preparation of iron oxide nanoparticles (MION) by employing the Musa acuminata pseudostem extract. The morphological aspects of MION were investigated using SEM and HR-TEM, revealing its spherical shape and size of 20 - 60 nm. The MION’s XRD spectra further supported their size to be 20 nm. The FTIR spectrum depicted the presence of phytochemicals in Musa acuminata pseudo stem extract. Antibacterial studies were performed to assess MION’s biocompatibility. The MION was subjected to remove sunset yellow FCF dye solution and batch adsorption parameters like pH (3.0), contact time (180 min), MION dosage (4 mg/100 mL) and initial dye concentration (15 mg/L) were optimized. It was also ascertained that the Freundlich isotherm and pseudo-first-order kinetics were found to be best fit with a maximum adsorption capacity of 8.93 mg/mg, respectively. The thermodynamic findings indicated that MION's adsorption process exhibited spontaneity and endothermicity. The effect of ionic strength and humic acid resulted in a corresponding enhancement and reduction in the removal efficacy for sunset yellow adsorption. The recyclability of MION exhibited consistent performance over five successive cycles with a 75.4% sunset yellow recovery rate. Therefore, MION is cost-effective and efficient in removing toxic dye pollutants.

Exploring Energy-Efficient Techniques and Chemical Kinetics in Reactive Nitrogen Species Production with Ambient Air Plasma for Plasma-Activated Water

This study investigates the chemical kinetics of reactive nitrogen species (RNS) formation in plasma-activated water (PAW) using ambient air and evaluates its energy efficiency. A singular plasma/liquid reactor was used, with discharge power varying between 16.4 to 27.0 W and agitation speeds set at 0 and 750 rpm. The reactor operated across temperatures from 5.00 to 35.00 °C during a consistent 180 min plasma activation. Analysis encompassed ionic strength effects, hydronium activity, conductivity, and iodide as a redox indicator for PAW. Findings suggest reactive species predominantly originate in the gas phase and move to the liquid through the gas-liquid interface. HNO3 production in PAW demonstrated a zero-order, temperature-dependent reaction. From activation parameters and ionic strength effects, a determinant step for aqueous HNO3 production was proposed. The influence of discharge power and agitation on HNO3 and HNO2 production was associated with heightened rates due to increased mass transfer and electric field strength. The research highlighted a trade-off between energy efficiency and nitrate production rate, emphasizing an efficiency peak of 72.33 nmol J-1 in PAW, pivotal for cost and operational benefits.

Separation of the heme protein cytochrome C using a 3D structured graphene oxide bionanocomposite as an adsorbent.

Proteins are of great importance for medicine and the pharmaceutical and food industries. However, proteins need to be purified prior to their application. This work investigated the application of a hydrogel bionanocomposite based on agar and graphene oxide (GO) for capturing cytochrome C (Cyto C) heme protein by adsorption from aqueous solutions with other proteins. Although applications of GO-based materials in adsorption are widely studied, the focus on semi-continuous processes remains limited. Adsorption experiments were carried out in batch and fixed bed columns. The effect of pH and ionic strength on adsorption was investigated, and there is evidence that electrostatic interactions between Cyto C and the nanocomposite were favoured at pH = 7; the adsorption capacity decreased as NaCl and KCl concentrations increased, ascribed to the weak electrostatic interaction between the protein and GO active sites in the bionanocomposite. All adsorption isotherm models (Langmuir, Freundlich, Sips) used gave suitable adjustments to the equilibrium experimental data and the kinetic models applied. The maximum adsorption capacity predicted by the Langmuir isotherm was ∼400 mgCytoC gadsorbent,dry-1, and the adsorption thermodynamics indicated a physisorption process. Tests were performed to evaluate the co-adsorption in batch, and the composite was effective in adsorbing Cyto C in solution with bovine serum albumin (BSA) and L-phenylalanine. Fixed bed tests were performed, and although protein adsorption onto nanoparticles can be challenging, the Cyto C adsorbed could be successfully recovered after desorption. Overall, the GO-based hydrogel was an effective method for cytochrome C adsorption, exhibiting a notorious potential for applications in protein separation processes.

LnDOTA puppeteering: removing the water molecule and imposing tetragonal symmetry.

Complexes of lanthanide(iii) ions (Ln) with tetraazacyclododecane-N,N',N'',N'''-tetraacetate (DOTA) are a benchmark in the field of magnetism due to their well-investigated and sometimes surprising features. Ab initio calculations suggest that the ninth ligand, an axial water molecule, is key in defining the magnetic properties because it breaks the potential C4 symmetry of the resulting complexes. In this paper, we experimentally isolate the role of the water molecule by excluding it from the metal coordination sphere without altering the chemical structure of the ligand. Our complexes are therefore designed to be geometrically tetragonal and strict crystallographic symmetry is achieved by exploiting a combination of solution ionic strength and solid state packing effects. A thorough multitechnique approach has been used to unravel the electronic structure and magnetic anisotropy of the complexes. Moreover, the geometry enhancement allows us to predict, using only one angle obtained from the crystal structure, the ground state composition of all the studied derivatives (Ln = Tb to Yb). Therefore, these systems also provide an excellent platform to test the validity and limitations of the ab initio methods. Our combined experimental and theoretical investigation proves that the water molecule is indeed key in defining the magnetic anisotropy and the slow relaxation of these complexes.

Waugh Type Polyoxometalate Enneamolybdomangate(IV) as an Acid Catalyst for Hydrolysis and as an Oxidant for Aspirin: A Kinetic Study

The oxidations of aspirin and salicylic acid by enneamolybdomanganate(IV) were studied in perchloric acid medium. The aspirin undergo hydrolysis prior to the oxidation to generate salicylic acid, which was found to be catalyzed by both HClO4 as well as the oxidant. The rate of hydrolysis of aspirin catalyzed by the oxidant was found to be lesser than that of HClO4. A mechanism based on the kinetic results is proposed for oxidation of both aspirin and salicylic acid. Initially, aspirin undergo hydrolysis to give salicylic acid, which is catalyzed by both the oxidant, which also acts as an acid catalyst and the HClO4 used. The salicylic acid generated in prior hydrolysis reacts with an oxidant undergoing oxidative decarboxylation by enneamolybdomanganate(IV) in a rate determining step generating phenol. Further oxidation of phenol by another oxidant molecule gives the final product p-benzoquinone in a fast step. The mechanism of oxidation of salicylic acid was also studied under identical conditions as that of aspirin and found to be similar except its prior hydrolysis. A plausible mechanism was proposed and the rate laws for both the substrates were derived. In order to understand the intervention of free radicals the reaction was studied in presence of added acrylonitrile. The formation of copious precipitate due to polymerization of added acrylonitrile was not observed and the values of kobs also remain constant in presence of added acrylonitrile. The formation of MnIII was also studied in presence of added tetrasodium pyrophosphate, which did not affect the values of kobs. Therefore, the formation of free radical and MnIII was excluded while proposing mechanisms for both the substrates. The effect of added products Mn2+ and molybdate also did not have any effects indicating no prior equilibria involving these two products. The effect of ionic strength and solvent polarity are in favour of the reaction between two neutral molecules. The activation parameters were determined and support an outer sphere reaction with formation of a weak precursor complex between the reactants was proposed for both aspirin and salicylic acid.

2D/3D MXene/NiFeMn-layered double hydroxide decorated gelatin for removal of Cr(VI) and Congo red: Performance and mechanism

The discharge of toxic heavy metals and dyes into water is considered a principal reason for ecosystem deterioration. Therefore, the development of versatile adsorbents that can treat this threat is an urgent issue. On this basis, we designed and characterized a novel Ti3C2TX/NiFeMn-LDH@Gel composite to aptly remove hazardous hexavalent chromium ions Cr(VI) and organic Congo red dye (CR). Ti3C2TX/NiFeMn-LDH@Gel composite was facilely synthesized by introducing NiFeMn-layered double hydroxide and Ti3C2TX MXene into gelatin via a cross-linking reaction. Experimental data revealed that raising Ti3C2TX amount to 10 % in the matrix has dramatically promoted the adsorption aptitude of Ti3C2TX/NiFeMn-LDH@Gel towards Cr(VI) and CR. Freundlich model best described Cr(VI) and CR adsorption, with qmax reaching 423.73 mg/g, and 588.24 mg/g, respectively. Additionally, the adsorption kinetics of Cr(VI) and CR were fitted to the pseudo-second order model accompanied with spontaneity, randomness, and endothermic behavior. In addition, stability, and selectivity of Ti3C2TX/NiFeMn-LDH@Gel were investigated. Effect of ionic strength and interfering ions were explored as well. Besides, the recyclability test inferred superb adsorption capacities towards Cr(VI) and CR till the 5th cycle, revealing the potentiality of Ti3C2TX/NiFeMn-LDH@Gel towards anionic contaminants removal.

Efficiency of electrocoagulation for simultaneous treatment of As and Mn in neutral mine water

Despite the efficiency and ease of implementation of electrocoagulation (ECG), its industrial application for the treatment of contaminated mine water is limited due to high energy and electrode consumption. The main objective of the present study was to identify the most performant ECG conditions using Fe–electrodes for the simultaneous removal of As(III) and Mn(II) from synthetic and surrogate neutral mine water, while limiting energy and electrode consumption. Treatability tests were performed on i) single synthetic effluents containing only 3.5mg/L As (SAs) or 4.5mg/L Mn (SMn), ii)binary synthetic effluents containing both As and Mn (SAs+Mn), and iii) surrogate mine water (Elow and Ehigh). The effect of current density (CD), ionic strength, and retention time were first evaluated for the treatment of SAs, SMn, and SAs+Mn. Then, the most performant conditions were used to treat Elow and Ehigh. The toxicity to Daphnia magna of Elow and Ehigh was evaluated before and after ECG treatment. The results showed that the increase of CD from 0.25 to 10 mA/cm2 greatly improved the removal of Mn and to a lesser extent of As, as well as energy and electrode consumption. Despite a negligible effect on the removal efficiency of As and Mn, the ionic strength (from 0.25 to 2.5mS/cm) and inter-electrode distance (from 10 to 50 mm) strongly affected the energy consumption. Results showed that ECG efficiently removed As (>97 %) from SAs at low CD (0.5 mA/cm2), while Mn required a 3.3-fold higher CD to achieve satisfactory removal (>60 %) from SMn. For the treatment of SAs+Mn, As removal was more efficient and faster than Mn removal (99 vs. 60 % and 20 vs. 60 min, respectively) at a CD of 2.0 mA/cm2. Moreover, the simultaneous removal of As and Mn at 2.0 mA/cm2 produced a volume of sludge 3.3 times greater than at 0.5 mA/cm2. Lastly, high As (99 %) and variable Mn (40–57 %) removal efficiencies were obtained after Elow and Ehigh treatment, with potential positive effect of the presence of Ca2+ and Cl- on the removal of As, while SO42- may have negatively affected the removal of Mn. After ECG treatment, no addition of toxicity to D. magna was observed for Elow and Ehigh. The outcomes of this study may provide promising insights for the application of ECG for simultaneous removal of metal(loid)s from contaminated mine water.

Adsorption Performance and Mechanisms of Tetracycline on Clay Minerals in Estuaries and Nearby Coastal Areas.

Clay minerals in sediments have strong adsorption capacities for pollutants, but their role in the distribution of antibiotics in estuaries and nearby coastal areas is unclear. We evaluated the clay mineral montmorillonite (SWy-2) adsorption capacity for tetracycline (TC). We assessed the adsorption capacity of SWy-2 for TC by measuring the removal percentage of 30 mg/L TC over time. The effects of pH and ionic strength on the TC adsorption onto SWy-2 were investigated. We analyzed the kinetics of TC adsorption using a pseudo-second-order model and determined the adsorption isotherm using the Langmuir equation. SWy-2 particles were characterized using zeta potential, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analyses before and after TC adsorption. The removal percentage of 30 mg/L TC by SWy-2 reached 70.76% within 0.25 h and gradually increased to 78.64% at 6 h. TC adsorption was influenced by pH and ionic strength, where low pH enhanced and high ionic strength reduced the adsorption. The kinetics of TC adsorption followed a pseudo-second-order model, and the adsorption isotherm adhered to the Langmuir equation. The saturated adsorption capacity (qmax) of SWy-2 for TC was 227.27 mg/g. Zeta potential, FTIR, and XRD analyses confirmed that electrostatic interactions and chemical bonds played a significant role in the TC adsorption by SWy-2. SWy-2 clay mineral exhibits a substantial adsorption capacity for TC, indicating its potential as an effective sorbent to mitigate antibiotic contamination in estuaries and nearby coastal areas. The observed effects of pH and ionic strength on TC adsorption have implications for the environmental fate and transport of antibiotics. The pseudo-second-order kinetic model and Langmuir isotherm equation provide valuable insights into the adsorption behavior and capacity of TC on SWy-2. Characterization analyses support the involvement of electrostatic interactions and chemical bonds in the SWy-2-TC adsorption mechanism.