Removal Of Ca2 Research Articles

Effectiveness of five instruments when removing calcium hydroxide paste from simulated internal root resorption cavities in extracted maxillary central incisors.

To evaluate the effectiveness of five instruments used for irrigant agitation during the removal of calcium hydroxide [Ca(OH)2 ] paste in simulated internal root resorption (IRR) cavities created in extracted maxillary central incisors. Seventy maxillary central incisors with a single canal were selected. The canals were accessed and instrumented with Reciproc R50, then the roots were split in the bucco-lingual direction and the halves separated. Simulated IRR cavities were created, in both halves of the roots, 5mm from the apex with a spherical bur. The specimens were reconstructed with cyanoacrylate glue and allocated into seven groups: negative control - no treatment; positive control - filled with Ca(OH)2 without performing any irrigation protocol; the other groups were divided according to the instrument used for irrigant agitation, namely: Ultrasonic, EndoActivator® , EDDY® , XP-endo® Finisher and XP-endo® Shaper. The specimens were cleaved and analysed using optical microscopy and scanning electron microscopy, to compare the Ca(OH)2 remnants between them. Then, theIRR cavities created by the burs were cleaned and subjected to a protocol of demineralization with 20% nitric acid, the roots reconstructed, and the irrigant agitation methods, as well as the microscopic analysis was repeated. Analysis of the images of Ca(OH)2 remaining in the simulated IRR cavities after irrigation was performed by two calibrated examiners based on a previously established scoring system. The data were statistically compared by Kruskal-Wallis test, Mann-Whitney U-test and Wilcoxon tests, with the significance level set at 5%. There was a significant difference in the effectiveness of the instruments in relation to the cavity creation method (bur vs. bur/acid) and evaluation method (optical microscopy and scanning electron microscopy) (P<0.05). The XP-endo® Finisher and EDDY® groups were associated with significantly more effective removal of Ca(OH)2 when the IRR cavities were created using the acid protocol and analysed by scanning electron microscopy. None of the instruments tested were able to completely remove the Ca(OH)2 pastefrom the simulated IRR cavities; however, the EDDY® and XP-endo® Finisher removed more Ca(OH)2 in the bur/acid cavity creation method analysed by scanning electron microscopy.

Are the typical organic components in biomass pyrolyzed bio-oil available for leaching of alkali and alkaline earth metallic species (AAEMs) from biomass?

In this study, six dominant organic compounds in biomass pyrolyzed bio-oil, composed of acidic compound (acetic acid) and non-acidic compound (furfural, hydroxyacetone, ethylene glycol, phenol, and guaiacol) were used to remove AAEMs from different lignocellulosic biomass (rice husk, cotton stalk, and fir sawdust) by leaching pretreatment. Other four conventional solutions (deionized water, hydrochloric acid solution, aqueous phase bio-oil, and simulated bio-oil) were selected as control eluents. Results showed that the removal rate of AAEMs was highly affected by the types of immersion solutions, pH values, and the species of biomass. Majority of K in biomass could be removed by leaching of acetic acid. Ca was more difficult to be removed by leaching of water and acetic acid, but could be removed by leaching of HCl. In general, the removal rate of K was highest among the four species of AAMEs by using five non-acidic components, followed by Na, Mg, and Ca. The use of five non-acidic solutions was significantly benefit for the remove of K, Mg, and Na, but, was less useful in removal of Ca in rice husk and fir sawdust. However, the removal rates of Ca in cotton stalk by leaching of phenol, guaiacol, and hydroxyacetone were increased to nearly three times than water leaching. A synergistic effect for removing AAEMs occurred between acetic acid and non-acidic components in bio-oil, indicating that the non-acidic compounds also play an important role in leaching of AAEMs.

Naja atra Cardiotoxin 3 Elicits Autophagy and Apoptosis in U937 Human Leukemia Cells through the Ca2+/PP2A/AMPK Axis.

Cardiotoxins (CTXs) are suggested to exert their cytotoxicity through cell membrane damage. Other studies show that penetration of CTXs into cells elicits mitochondrial fragmentation or lysosome disruption, leading to cell death. Considering the role of AMPK-activated protein kinase (AMPK) in mitochondrial biogenesis and lysosomal biogenesis, we aimed to investigate whether the AMPK-mediated pathway modulated Naja atra (Taiwan cobra) CTX3 cytotoxicity in U937 human leukemia cells. Our results showed that CTX3 induced autophagy and apoptosis in U937 cells, whereas autophagic inhibitors suppressed CTX3-induced apoptosis. CTX3 treatment elicited Ca2+-dependent degradation of the protein phosphatase 2A (PP2A) catalytic subunit (PP2Acα) and phosphorylation of AMPKα. Overexpression of PP2Acα mitigated the CTX3-induced AMPKα phosphorylation. CTX3-induced autophagy was via AMPK-mediated suppression of the Akt/mTOR pathway. Removal of Ca2+ or suppression of AMPKα phosphorylation inhibited the CTX3-induced cell death. CTX3 was unable to induce autophagy and apoptosis in U937 cells expressing constitutively active Akt. Met-modified CTX3 retained its membrane-perturbing activity, however, it did not induce AMPK activation and death of U937 cells. These results conclusively indicate that CTX3 induces autophagy and apoptosis in U937 cells via the Ca2+/PP2A/AMPK axis, and suggest that the membrane-perturbing activity of CTX3 is not crucial for the cell death signaling pathway induction.

Exploring calcium ion-dependent effect on the intermolecular interaction between human secreted phospholipase A2 and its peptide inhibitors in coronary artery disease

Human secreted phospholipase A2 (hsPLA2) is a small calcium ion (Ca2+)-regulatory protein secreting from platelets, eosinophils and T-lymphocytes, which has been established as an important biomarker and potential target for the diagnosis and therapy of coronary artery disease. Short peptide inhibitors are used to competitively suppress the enzymatic activity of hsPLA2. Here, Ca2+ effect on the intermolecular recognition and interaction between hsPLA2 and its peptide inhibitors is investigated systematically by using molecular modeling and bioinformatics analysis. Dynamics simulations reveal that the hsPLA2 structure bound with Ca2+ is rather stable and has low thermal motion; removal of Ca2+ considerably increases structural flexibility and intrinsic disorder of the protein. Energetics calculations suggest that presence of Ca2+ can effectively promote the interaction of hsPLA2 with peptide inhibitors. In particular, the local substructures of hsPLA2 such as helix H1, loop L2 and double-stranded β-sheet DS that participate in peptide recognition are involved in or nearby Ca2+-coordinating site and can be directly stabilized by the Ca2+. In addition, a significant concentration-dependent effect of Ca2+ on peptide–hsPLA2 binding is observed in vitro, that is, a little of Ca2+ can largely improve peptide binding affinity, but high Ca2+ concentration does not increase the affinity substantially. The correlation between calculated free energy and experimental binding affinity over different peptide inhibitors is improved considerably by adding Ca2+ to hsPLA2. Specifically, the FLSYK peptide can generally bind to Ca2+-bound hsPLA2 with a moderate or high affinity (Kd ranges between 56 and 210 μM), but have only a modest affinity or even nonbinding to Ca2+-free hsPLA2 (Kd > 400 μM or = n.d.).

Efficacy of Different Irrigation Systems Used to Remove Calcium Hydroxide from the Root Canal

Introduction: The present study aimed to compare the cleaning efficacy of passive ultrasonic irrigation (PUI), self-adjusting file (SAF), EndoVac, and conventional syringe irrigation (CSI) techniques on Ca(OH)2 removal from the root canal. Methods: This study was conducted on the mesial roots of 36 human mandibular molar teeth. After 1 month, the Ca(OH)2 was removed from the experimental groups using four different irrigation techniques (SAF, PUI, EndoVac, and CSI). The inner surfaces of the canals were examined using a stereomicroscope at 30x magnification. The assessment of remaining Ca(OH)2 medicament in the grooves was performed by three calibrated dentists using a scoring system ranged 0-3. Results: None of the groups showed complete Ca(OH)2 removal from the root canals. The PUI technique removed significantly more Ca(OH)2 from all root canals, compared to EndoVac and CSI techniques (P<0.05). In the apical third, SAF group results were significantly better than the CSI group results (P<0.05). In the middle third, the SAF technique led to significantly better results in the removal of Ca(OH)2, compared to the techniques used in other groups (P<0.05).Conclusion: Currently, there is no irrigation system that can completely remove Ca(OH)2 from the root canal in endodontics. Regarding the removal of Ca(OH)2 from root canals, the PUI technique was significantly better than EndoVac and CSI techniques. In addition, the SAF technique showed significant efficacy in the middle third of the root canals.

Method for Preparation of Nutrient-depleted Soil for Determination of Plant Nutrient Requirements

ABSTRACTResearch for nutrient optimization and crop nutrient use efficiency requires precise control on soil nutrient status. While nutrient-depleted soils are preferable to artificial soils or hydroponics, reliable and affordable methods for nutrient removal are lacking. We report the systematic standardization and validation of a simple method to wash soil with purified deionized water for the removal of nutrients such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and organic carbon. Sandy soil was washed with RO water (1:1, w/v) followed by several washes with Type 1 ultrapure water (2:1, w/v) and tested after each wash for the removal of organic carbon, N, P, K, and Ca. After seven washes, total dissolved solids (TDS) were reduced to 5 ppm, conductivity to 10 µS, organic carbon content was reduced by 78%, while N by 19.5%, P by 30%, K by 48% and Ca by 29%. Two genotypes of rice were grown for full life cycle under normal and low N fertilizer (urea) levels to demonstrate that soil depleted with nutrients by our method supports normal plant growth in the greenhouse and allows experiments impossible under field conditions. Precise control on the nutrient status of the soil by our method also helped demonstrate yield differences between genotypes and N regimes and also that higher grain yields can be obtained with low nitrogen (N) input. Thus, our method facilitates better design of experiments for precise determination of nutrient requirements for crop growth and nutrient use efficiency.

REMOVAL IMPURITIS GARAM DENGAN METODE PERTUKARAN ION SECARA BATCH

Salt is one of the consumer and industrial consumption products that has the maincontent of sodium chloride (NaCl). The present quality of the salt product currentlycontains about 90-93% sodium chloride, and the other is known as an impurities ofcalcium (Ca), magnesium (Mg), potassium (K) and sulfate (SO4) ions. The presence ofthese impurities will decrease the quality of the salt product, so a method is needed todecrease the content of impurities in the salt product. One of the methods that can beused to reduce the levels of impurities such as Ca, Mg, K, and sulfate (SO4) ions in saltsolution is ion exchange method. In this study we studied the effect of cation resinamount (50-150) grams per liter of salt solution and anion solution (150 grams) andcontact time (5-25) minutes on removal of Ca, Mg, K and SO4 ions. The study wasconducted in a stirred tank with a fixed rotation speed of 200 rpm, and the initial qualityof the salt solution contained Ca ions: 0.07%, Mg: 0.09%, K: 0.04% and SO4: 0.4%.Based on the result of the research, the removal of Ca ion: 93.6%, Mg: 78.93%, K:25.00% dan SO4: 85.47 % at condition of cation resin amount: 150 gram/liter andcontact time 25 minutes.

An extraction and precipitation process for the removal of Ca and Mg from ammonium sulfate rare earth wastewaters

Softening ammonia sulfate wastewater is one of the vital issues in the rare earth industry. In this article, a novel softening process using [4,4′-isopropylidenebis (phenoxyacetate)] (H2IPOAA) for Ca2+ and Mg2+ (M2+) is developed. The effect factors, i.e., equilibrium time, pH value of aqueous phase and saponification degree are investigated. The extraction mechanism is proposed to be cation exchange. With a saponification degree of 85%, H2IPOAA is successfully used for the precipitation of Ca2+ and Mg2+ from ammonia sulfate wastewater within 10 min. The process can form precipitated particles with an average size of 35 μm, which are much larger than the precipitates formed by H2C2O4, Na2C2O4 and Na2CO3. The precipitated particles can be easily separated from the raffinate. In addition, H2IPOAA is repeatedly used for five times with a little loss. To a considerable extent, the reuse of H2IPOAA contributes to lowering the cost and reducing the pollution. The concentrations of Ca2+ and Mg2+ in the raffinate extracted by H2IPOAA are up to the MVR standard for wastewater treatment. The economical and efficient softening process meets the need of green chemistry, which is expected to replace traditional industrial processes for water softening based on H2C2O4, Na2C2O4 and Na2CO3.

Use of a microelectrode array to record extracellular pacemaker potentials from the gastrointestinal tracts of the ICR mouse and house musk shrew (Suncus murinus)

BackgroundThe rhythmic contraction and relaxation of smooth muscles in the gastrointestinal (GI) tract is governed by pacemaker electrical potentials, also termed slow waves, which are calcium currents generated by interstitial cells of Cajal (ICCs). Malfunction of pacemaker rhythms contributes to a number of clinically challenging gastrointestinal motility disorders. MethodA microelectrode array (MEA) was used to record slow waves in vitro from intact GI tissues freshly isolated from the ICR mouse and Suncus murinus. The effects of temperature, extracellular calcium and potassium concentrations on pacemaker potentials were quantified using spatiotemporal metrics. ResultsPacemaker frequency decreased from the duodenum to the ileum in the mouse, but this phenomenon was less significant in Suncus murinus. In both the mouse and Suncus murinus, the stomach had a much lower pacemaker frequency than the intestine. Propagation velocity and amplitude were highest in the proximal intestine. Temperature significantly increased pacemaker frequency in the intestinal tissues of both species. Removal of Ca2+ from the medium inhibited pacemaker potential and increasing the Ca2+ concentration increased pacemaker frequency in the mouse ileum. Increasing K+ concentration decreased pacemaker frequency in the absence of nifedipine. ConclusionsThe MEA allows efficient investigation of gut pacemaker frequency and propagation.

Energy Efficient Phosphorus Recovery by Microbial Electrolysis Cell Induced Calcium Phosphate Precipitation

Phosphorus (P) removal and recovery from waste streams is essential for a sustainable world. Here, we updated a previously developed abiotic electrochemical P recovery system to a bioelectrochemical system. The anode was inoculated with electroactive bacteria (electricigens) which are capable of oxidizing soluble organic substrates and releasing electrons. These electrons are then used for the reduction of water at the cathode, resulting in an increase of pH close to the cathode. Hence, phosphate can be removed with coexisting calcium ions as calcium phosphate at the surface of the cathode with a much lower energy input. Depending on the available substrate (sodium acetate) concentration, an average current density from 1.1 ± 0.1 to 6.6 ± 0.4 A/m 2 was achieved. This resulted in a P removal of 20.1 ± 1.5% to 73.9 ± 3.7%, a Ca removal of 10.5 ± 0.6% to 44.3 ± 1.7% and a Mg removal of 2.7 ± 1.9% to 16.3 ± 3.0%. The specific energy consumption and the purity of the solids were limited by the relative low P concentration (0.23 mM) in the domestic wastewater. The relative abundance of calcium phosphate in the recovered product increased from 23% to 66% and the energy consumption for recovery was decreased from 224 ± 7 kWh/kg P to just 56 ± 6 kWh/kg P when treating wastewater with higher P concentration (0.76 mM). An even lower energy demand of 21 ± 2 kWh/kg P was obtained with a platinized cathode. This highlights the promising potential of bioelectrochemical P recovery from P-rich waste streams.

MILD HYPOXIA/ACIDOSIS INCREASE THE FREQUENCY OF CALCIUM OSCILLATIONS TO AUGMENT SECRETORY ACTIVITY IN RAT CAROTID BODY CHEMORECEPTORS

In carotid body (CB) chemoreceptors (Type 1/gloms cells), severe levels of hypoxia (<1%O2) and acidosis (pH 5.0–6.5) are well known to produce strong depolarization and sustained elevation of intracellular [Ca], which enhances transmitter secretion. We studied the effects of mild and moderate levels of hypoxia (2–5%O2) and acidosis (pH7.0–7.3) on cell membrane potential (Em), Ca signaling and catecholamine secretion in Type 1 cells isolated from 3–4 week-old rats. Spontaneous Ca oscillations of varying frequency and amplitude were observed under normoxic conditions in many individual Type 1 cells in cluster. The frequency and amplitude of Ca oscillations were perfusion flow- and temperature-dependent. Verapamil (an inhibitor of both T- and L- type Ca channels), 2-APB (inhibitor of IP3 receptor and store-operated Ca entry) and removal of external Ca abolished Ca oscillations. Mild/moderate hypoxia (2–5%O2) produced low level depolarization (<12 mV) and increased the frequency and amplitude of Ca oscillations. Mild/moderate acidosis (pH 7.0–7.2) also produced small depolarization (<15 mV) and increased the frequency and amplitude of Ca oscillations. These effects of hypoxia and acidosis were reduced to varying degrees by Ca channel inhibitors, but were not inhibited by amiloride. In CB slices, both hypoxia and acidosis caused small increases in catecholamine secretion as assessed by amperometry. These findings show that mild hypoxia and acidosis increase the frequency and amplitude of Ca oscillations, thereby augmenting the secretory activity of the CB. Support or Funding Information This work was supported by funding from NIH Ca oscillations in gloms cells: effect of 2-APB This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Velocity and wall shear stress of 18% EDTA irrigation solution flow in the removal of Ca(OH)2 with computational fluid dynamic analysis

Introduction: Ethylene Diamine Tetra Acetic Acid (EDTA) 18% irrigation solution is one of the chelating agents that able to remove calcium hydroxide (Ca(OH)2) from the root canal wall. Failure of root canal treatment can be caused by the presence of residual calcium hydroxide in the root canal wall, thus blocking the bond between the medication and root canal filling material with the root canal wall. This study was aimed to observe the EDTA 18% flow in removing the Ca(OH)2 using CFD analysis. Methods: This research was descriptive. Cleanliness of the root canal wall from Ca(OH)2 medicament using EDTA 18% irrigation was analysed using the CFD method with test specimens in the form of resin blocks made according to the characteristics of the root canal. The irrigation needle used was side-vented with a position of 3 mm from the apical tooth. Stage analysis of root canal geometry was performed using Computational Fluid Dynamics (CFD) analysis to observe the characteristics of irrigation solutions in root canals in 3D. Results: The streamlined characteristics of EDTA 18% irrigation solution showed a unique behaviour due to the features of the side-vent shaped irrigation needle. Irrigation flow in the crown area of the inlet (side-vented irrigation needle) showed low velocity so that the fluid flow when exiting the inlet was more towards the apical than the outlet (root canal orifice). Conclusion: Velocity and wall shear stress of EDTA 18% showed the results validation conformity between experimental and CFD, that the maximum velocity of EDTA 18% is 19 ms-1 and EDTA 18% wall shear stress is 1.56 KPa for calcium hydroxide removal observed from the CFD study. Keywords: Computational fluid dynamics, EDTA 18%, calcium hydroxide (Ca(OH)2), velocity, wall shear stress

Geochemical characteristics of the eolian deposits in the Zoigê basin and their implications for provenance and weathering intensity

Eolian deposits in the Zoigê basin at the northeastern region of the Tibetan Plateau (TP) were analyzed for their major-trace elements and SmNd isotopic compositions to explore the provenance and weathering intensity. The results are compared with the data from the Lingtai section (LT) in the Chinese Loess Plateau (CLP). Eolian deposits from different sections in the Zoigê basin have resembling geochemical compositions, reflecting similar provenance. Their major element compositions are close to those of the UCC, and their UCC-normalized major-trace element abundances and chondrite-normalized rare earth element (REE) abundances are similar to the LT samples. However, the SiO2, Al2O3, TiO2, Zr, Hf, Sc, Co, V, Ni concentrations and SiO2/TiO2, TiO2/Al2O3, Co/Th, La/Sc, Th/Sc, εNd(0), 147Sm/144Nd ratios of the Zoigê sections are quite different from those of the LT section, which suggests different provenances for the eolian deposits in these two regions. The relatively high abundances of SiO2, Zr, Hf and low abundances of trace elements indicate that local sediments on the TP are the major contributors to the eolian deposits in the Zoigê basin. Eolian deposits from the Zoigê basin have experienced the early Na and Ca removal stage, and chemical weathering parameters suggest a moderate weathering condition in the source and deposition regions.

Influence of Cell Configuration and Long-Term Operation on Electrochemical Phosphorus Recovery from Domestic Wastewater.

Phosphorus (P) is an important, scarce, and irreplaceable element, and therefore its recovery and recycling are essential for the sustainability of the modern world. We previously demonstrated the possibility of P recovery by electrochemically induced calcium phosphate precipitation. In this Article, we further investigated the influence of cell configuration and long-term operation on the removal of P and coremoved calcium (Ca), magnesium (Mg), and inorganic carbon. The results indicated that the relative removal of P was faster than that of Ca, Mg, and inorganic carbon initially, but later, due to decreased P concentration, the removal of Ca and Mg became dominant. A maximum P removal in 4 days is 75% at 1.4 A m–2, 85% at 8.3 A m–2 and 92% at 27.8 A m–2. While a higher current density improves the removal of all ions, the relative increased removal of Ca and Mg affects the product quality. While the variation of electrode distance and electrode material have no significant effects on P removal, it has implication for reducing the energy cost. A 16-day continuous-flow test proved calcium phosphate precipitation could continue for 6 days without losing efficiency even when the cathode was covered with precipitates. However, after 6 days, the precipitates need to be collected; otherwise, the removal efficiency dropped for P removal. Economic evaluation indicates that the recovery cost lies in the range of 2.3–201.4 euro/kg P, depending on P concentration in targeted wastewater and electrolysis current. We concluded that a better strategy for producing a product with high P content in an energy-efficient way is to construct the electrochemical cell with cheaper stainless steel cathode, with a shorter electrode distance, and that targets P-rich wastewater.

Integrated submerged membrane distillation-adsorption system for rubidium recovery

Seawater reverse osmosis (SWRO) brine management is essential for desalination. Improving brine recovery rate with resource recovery can enhance the overall desalination process. In this study, an integrated submerged membrane distillation (S-MD) with adsorption (granular potassium copper hexacyanoferrate (KCuFC)) was evaluated for improving water recovery from brine while extracting valuable Rb. The thermal S-MD process (55 °C) with a continuous supply of Rb-rich SWRO brine enabled Rb to be concentrated (99% rejection) while producing fresh water. Concentrated Rb in thermal condition enhanced Rb extraction by granular KCuFC. An optimum dose (0.24 g/L) KCuFC was identified based on 98% Rb mass adsorption (9.78 mg as Rb). The integrated submerged MD-adsorption system was able to achieve more than 85% water recovery and Rb extraction in continuous feed supply (in two cycles). Ca in SWRO brine resulted in CaSO4 deposition onto the membrane and surface of KCuFC, reducing recovery rate and Rb adsorption. MD water recovery significantly improved upon Ca removal while achieving a total of 6.65 mg of Rb extraction. In comparing the performance of different KCuFC forms (granular, particle and powder), the particle form of KCuFC exhibited 10–47% higher capacity in terms of total adsorbed Rb mass and adsorption rate.

Evaluating the impact of nano-magnesium calcite waste on the performance of cement mortar in normal and sulfate-rich media

The motivation behind this work is to evaluate the impact of nano-magnesium calcite (NMC) waste on the performance of cement mortar (CM) and its resistivity to sulfate attack. The addition of urea and urease enzyme to ground water resulted in the removal of Ca2+ and Mg2+ as NMC precipitate (byproduct of treatment process). As a beneficial recycling method, NMC with different proportions were individually blended with CM to enhance its performance in normal and sulfate-rich media. The results revealed that the NMC has a positive impact on the early-ages compressive strength of CM. Where, the addition of 1 wt% of NMC led to a significant enhancement in the rates of strength development and total porosity reduction at all ages of hydration. Comparing with reference mixture, a highest performance in sulfate medium was obtained in case of all CMs containing NMC. Complementary, the CM incorporated with 1 wt% NMC showed the highest resistance to sulfate attack (up to 12-months) which associated with lower compressive strength regression, total porosity increment, sulfate expansion and consequently lower ettringite formation rate.

Excitation of murine cardiac myocytes by nanosecond pulsed electric field.

Opening of voltage-gated sodium channels takes tens to hundreds of microseconds, and mechanisms of their opening by nanosecond pulsed electric field (nsPEF) stimuli remain elusive. This study was aimed at uncovering the mechanisms of how nsPEF elicits action potentials (APs) in cardiomyocytes. Fluorescent imaging of optical APs (FluoVolt) and Ca2+ -transients (Fluo-4) was performed in enzymatically isolated murine ventricular cardiomyocytes stimulated by 200-nanosecond trapezoidal pulses. nsPEF stimulation evoked tetrodotoxin-sensitive APs accompanied or preceded by slow sustained depolarization (SSD) and, in most cells, by transient afterdepolarization waves. SSD threshold was lower than the AP threshold (1.26 ± 0.03 vs 1.34 ± 0.03 kV/cm, respectively, P < 0.001). Inhibition of l-type calcium and sodium-calcium exchanger currents reduced the SSD amplitude and increased the AP threshold ( P < 0.05). The threshold for Ca 2+ -transients (1.40 ± 0.04 kV/cm) was not significantly affected by a tetrodotoxin-verapamil cocktail, suggesting the activation of a Ca 2+ entry pathway independent from the opening of Na + or Ca 2+ voltage-gated channels. Removal of external Ca 2+ decreased the SSD amplitude ( P = 0.004) and blocked Ca 2+ -transients but not APs. The incidence of transient afterdepolarization waves was decreased by verapamil and by removal of external Ca 2+ ( P = 0.002). The study established that nsPEF stimulation caused calcium entry into cardiac myocytes (including routes other than voltage-gated calcium channels) and SSD. Tetrodotoxin-sensitive APs were mediated by SSD, whose amplitude depended on the calcium entry. Plasma membrane electroporation was the most likely primary mechanism of SSD with additional contribution from l-type calcium and sodium-calcium exchanger currents.

Highly efficient removal of phosphonates from water by a combined Fe(III)/UV/co-precipitation process

Considerable amount of phosphorous is present as organic phosphonates (usually in the form of metal complexes, e.g., Ca(II)-phosphonate) in domestic and industrial effluents, which cannot be effectively removed by traditional processes for phosphate. Herein, we employed a proprietary process, i.e., Fe(III) displacement/UV irradiation/co-precipitation (denoted Fe(III)/UV/NaOH), to enable an efficient removal of Ca(II)-phosphonate complexes from water. The combined process includes three basic steps, i.e., Fe(III) replacement with the complexed Ca(II) to form Fe(III)-phosphonate of high photo-reactivity, UV-mediated degradation of Fe(III)-phosphonate to form phosphate and other intermediates, and the final phosphorous removal via co-precipitation at pH = 6. The operational conditions for the combined process to remove a typical phosphonate Ca(II)-NTMP (nitrilotrismethylenephosphonate) are optimized, where ∼60% NTMP is transformed to phosphate with the total phosphorous reduction from 1.81 mg/L to 0.17 mg/L. Under UV irradiation, the cleavage of NTMP is identified at the C-N and C-P bonds to form the intermediate products and phosphate in sequence. Also, the combined process is employed for treatment of two authentic effluents before and after activated sludge treatment, resulting in the phosphorous drop from 4.3 mg/L to 0.23 mg/L and from 0.90 mg/L to 0.14 mg/L respectively, which is much superior to other processes including Fenton/co-precipitation. In general, the combined process exhibits great potential for efficient removal of phosphonates from contaminated waters.

Fate of calcium, magnesium and inorganic carbon in electrochemical phosphorus recovery from domestic wastewater

Calcium (Ca), magnesium (Mg), phosphate and (bi)carbonate are removed simultaneously in electrochemical recovery of phosphorus (P) from sewage. However, the fate of these ions is not completely understood yet. In this paper, through wastewater acidification and current density altering, we clarified the precipitation process and electrochemical interaction of phosphate and coexisting ions. The removal of P is attributed to amorphous calcium phosphate (ACP) formation, whereas the removal of bicarbonate is mainly due to calcite (CaCO3) formation and acid-base neutralization. While both ACP and calcite results in Ca removal, Ca predominantly ends up in calcite. For Mg, it is exclusively removed as brucite (Mg(OH)2). Regardless of the acidification, 53 ± 2% P and 32 ± 1% Mg were removed in 24 h at 8.3 A/m2. By contrast, in response to the acidification, the removal of Ca dropped from 42% to 19%. The removal of Mg depends on the current density, with less than 5% removed at 1.4 A/m2 but 70% at 27.8 A/m2 in 24 h. Based on the precipitation mechanisms, the formation of calcite and brucite can be reduced by acidification and operating at a relatively low current density, respectively. Accordingly, we achieved the lowest Ca/P molar ratio (1.8) and the highest relative abundance of ACP in the precipitates (75%) at bulk pH 3.8 with a current density of 1.4 A/m2.

Effective removal of calcium and magnesium sulfates from wastewater in the rare earth industry.

The wastewater discharged from the rare earth (RE) industry generally contains a high level of calcium and magnesium sulfates, which confers permanent hardness and causes difficulties in recycling this wastewater. In this study, the alkyl phenoxy acetic acid derivatives including 4-methyl phenoxy acetic acid (M-POAA), 4-tert-butyl phenoxy acetic acid (B-POAA) and 4-tert-octyl phenoxy acetic acid (O-POAA), were synthesized via the Williamson reaction and characterized by nuclear magnetic resonance (NMR), infrared (IR), and ultra-violet (UV) spectroscopy, as well as elemental analysis and X-ray diffraction (XRD). Synthesis of the POAAs were simple and green, and the raw materials used for their production are widely available and low-cost. The potential for removal of Ca and Mg sulfates from industrial wastewater using POAAs as the organic precipitants was assessed. The total precipitation efficiencies of Ca and Mg from wastewater with the use of POAAs increased with the following order: M-POAA < B-POAA < O-POAA. The residual concentrations of Ca and Mg using O-POAA as the precipitant were lower than 0.099 and 0.089 g L−1, respectively. The O-POAA could be regenerated five times without any significant change in its structure and precipitation performance. Thus, the use of the novel precipitants is a prospective alternative to the conventional processes for softening wastewater.