Removal Of Calcium Research Articles

Beyond dumping: New strategies in the separation of preservative salt from tannery waste mixed salt and its reuse for tannery industrial application

The tannery effluent treatment plants produce tonnes of waste in the form of mixed salts containing sodium chloride, sulfate, calcium, and magnesium salts. Disposal of these mixed salts may create an environmental problem. The proposed method broadly consists of the separation of sodium chloride from reverse osmosis (RO) reject and raw-hide waste salt (preservative salt) of the tannery. This study used the physicochemical method to treat waste salt from tannery industrial waste. The addition of sodium hydroxide and sodium carbonate improved calcium and magnesium removal efficiency in the RO reject and preservative waste salts. The optimization of the sodium salt of hydroxide and carbonate is very important to remove an unwanted substance from waste salt. The sodium chloride was recovered, and the purity was about >98% which was successfully reused as preservative salt as well as in the pickling process in the tannery industry.

Role of hyperpolarization-activated cyclic nucleotide-gated channel HCN2 in embryonic neural stem cell proliferation and differentiation

Hyperpolarization-activated cyclic nucleotide-gated channels (HCN channels) are involved in spontaneous activity in many electrically active cell types such as cardiomyocytes and neurons. In this study, the role of HCN channels in proliferation and migration of Nestin and Sox2 expressing embryonic neural progenitor cells (NPC) originating from the subventricular zone (SVZ) was examined. Immunostaining and PCR data showed that the HCN2 subtype was highly expressed in these cells. Patch clamp recordings revealed a hyperpolarization-activated current, which was sensitive to inhibitors of HCN channels. Using the fluorescence dye bis-(1,3-dibutylbarbituric acid)-trimethineoxonol (DiBAC(4)(3)) we found that a prompt reduction of the extracellular K+ concentration, or exposing the cells to acute hypoxia, induced an instant hyperpolarization in the whole cell population. Recovery from low K+ induced hyperpolarization after extracellular calcium removal, or by re-oxygenation of hypoxic cells, was sensitive to ZD7288, a HCN channel inhibitor. Treatment of neurosphere cultures from the SVZ with ZD7288 caused a significant and reversible inhibition of neurosphere formation from single cells indicating that proliferation of progenitor cells was reduced. Furthermore, the migration of neuronal cells from neurospheres was considerably retarded in the presence of ZD7288. The results suggest that HCN2 channels are involved in controlling the proliferation of NPC and that HCN2 channel-induced spontaneous electrical activity may trigger the motility response of neurosphere-derived neurons in concert with other ion channels. Furthermore, the response to hypoxia suggests that HCN2 channels may trigger the chemotactic response of NPC to ischemic brain regions seen in many studies.

Comparative study on simultaneous removal of calcium and sulfate ions from flotation recycling water by aluminum hydroxide

Due to the environmental policies and economic reasons, the water used in some flotation operations of complex sulfide ores is recirculated, causing the ion concentration of some species to increase over time, affecting the flotation of the minerals of interest. In this work, an experimental and thermodynamic analysis of the synthetic solutions was presented with a high content of calcium and sulfate ions. The study focused on evaluating the use of two aluminum compounds for the precipitation of Ca2+ and SO42− in the form of ettringite. The amorphous aluminum hydroxide was found to be more efficient than the crystalline one, giving rise to 83% calcium and 91% sulfate removal. The XRD analysis of the solids showed the main reaction product of ettringite, accompanied by small amounts of calcite, due to the absorption of atmospheric carbon dioxide. The final solution after the chemical treatment showed residual calcium and sulfate concentrations below 200 mg/L. Finally, the kinetics of calcium removal appeared to correspond to a second order reaction with respect to calcium concentration, with an apparent activation energy of 53.48 kJ/mol, which may suggest that the ettringite precipitation process is governed by the chemical reaction.

Aortic Stiffness in L-NAME Treated C57Bl/6 Mice Displays a Shift From Early Endothelial Dysfunction to Late-Term Vascular Smooth Muscle Cell Dysfunction.

Introduction and Aims: Endothelial dysfunction is recognized as a cardiovascular aging hallmark. Administration of nitric oxide synthase blocker N-Ω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) constitutes a well-known small animal model of cardiovascular aging. Despite extensive phenotypic characterization, the exact aortic function changes in L-NAME treated mice are largely unknown. Therefore, this study presents a longitudinal characterization of the aortic reactivity and biomechanical alterations in L-NAME treated C57Bl/6 mice. Methods and Results: Male C57Bl/6 mice were treated with L-NAME (0.5 mg/ml drinking water) for 1, 2, 4, 8, or 16 weeks. Peripheral blood pressure measurement (tail-cuff) and transthoracic echocardiograms were recorded, showing progressive hypertension after 4 weeks of treatment and progressive cardiac hypertrophy after 8–16 weeks of treatment. Aortic stiffness was measured in vivo as aortic pulse wave velocity (aPWV, ultrasound) and ex vivo as Peterson modulus (Ep). Aortic reactivity and biomechanics were investigated ex vivo in thoracic aortic rings, mounted isometrically or dynamically-stretched in organ bath set-ups. Aortic stiffening was heightened in L-NAME treated mice after all treatment durations, thereby preceding the development of hypertension and cardiac aging. L-NAME treatment doubled the rate of arterial stiffening compared to control mice, and displayed an attenuation of the elevated aortic stiffness at high distending pressure, possibly due to late-term reduction of medial collagen types I, III, and IV content. Remarkably, endothelial dysfunction, measured by acetylcholine concentration-response stimulation in precontracted aortic rings, was only observed after short-term (1–4 weeks) treatment, followed by restoration of endothelial function which coincided with increased phosphorylation of endothelial nitric oxide synthase (S1177). In the late-disease phase (8–16 weeks), vascular smooth muscle cell (VSMC) dysfunction developed, including increased contribution of voltage-dependent calcium channels (assessed by inhibition with diltiazem), basal VSMC cytoplasmic calcium loading (assessed by removal of extracellular calcium), and heightened intracellular contractile calcium handling (assessed by measurement of sarcoplasmic reticulum-mediated transient contractions). Conclusion: Arterial stiffness precedes peripheral hypertension and cardiac hypertrophy in chronic L-NAME treated male C57Bl/6 mice. The underlying aortic disease mechanisms underwent a distinct shift from early endothelial dysfunction to late-term VSMC dysfunction, with continued disease progression.

Effect of process variables on producing biocoals by hydrothermal carbonisation of pine Kraft lignin at low temperatures

Lignin from pulping is recovered in a wet form, making it ideal for hydrothermal carbonisation (HTC). This study investigates the effects of temperature (200–280 °C), residence time (1–6 h), and water to biomass mass ratio (2:1–6:1) on the composition of the resultant biocoal and the extent of alkaline and alkaline metal removal during HTC of pine Kraft lignin (PKL). Consistent with studies on other biomass materials, temperature exhibited the most significant effect on biocoal yield and properties, followed by residence time showing a marginal effect and varying the water to lignin mass only affecting alkaline and alkaline earth metals removal. Biocoal yields were in the range of 76–95 % (80–97 % on a carbon basis) and, compositionally, the biocoal obtained corresponded to sub-bituminous (220–260 °C) and high volatile bituminous coals (280 °C). Gas yields are low with the gas comprising mainly CO2 (98 v/v). The optimum temperature, time and biomass to water ratio for alkaline and alkaline earth metals removal was 260 °C, 3 h and 5:1 under which 93–95 % for sodium (Na) and potassium (K) and 75–80 % for magnesium (Mg) and calcium (Ca) removal were achieved. Solid-state 13C Nuclear Magnetic Resonance (NMR) revealed that during HTC, the oxygen-containing bonds of esters, ethers, and carboxylic groups were dissociated to produce lower-molecular weight including phenolic compounds dissolved in the process water. These findings have shown that the HTC is a promising alternative thermochemical route for coalification of wet PKL to a low ash coal-like fuel similar to sub-bituminous coal in rank that has potential applications for carbonisation.

Comprehensive demetallization of crude oil using spherical polyelectrolyte brushes with submicron polybutadiene latex as a core

AbstractStable oil‐soluble metals complexes in crude oil bring various problems to the oil processing. In the previous work, four spherical polymer brushes with SiO2 as a core showed high nickel and calcium removal efficiency, but SiO2 has high density and smaller specific surface area, greatly limiting the demetallization efficiency. In the present work, spherical polyelectrolyte brushes (PAA@PB) were synthesized by emulsion grafting polymerization. DLS and TEM show that PAA@PB exhibits a uniform spherical core‐shell structure with a diameter of 526.3 nm, and TGA exhibits that the grafting rate is 20.6%. The demetallization rate and selectivity of PAA@PB were investigated with varying concentration, electrical desalination conditions, pH value, and NaCl concentration. In contrast, the demetallization efficiency of PAA@PB is much greater than that of PAA@SiO2‐G. Notably, PAA@PB exhibits excellent nickel removal efficiency, but a little more selective for iron. The optimal removal rate for calcium, nickel, and iron are 55.3%, 52.6%, and 46.1%, respectively. Compared with P4VP@SiO2‐G, which possesses the highest demetallization efficiency among four polymer brushes with SiO2, to achieve the same nickel removal rate, the concentration of PAA@PB is almost eight times less than that of P4VP@SiO2‐G. Consequently, PAA@PB has great potential as an excellent comprehensive demetallization agent.

Contaminants Removal from Wastewater of LFP Batteries Recycling Process Using Adsorption Methods

Wastewater from the LFP battery cathode recycling process still contains metals such as lithium, calcium, sodium, and silica. Adsorption method was used to remove metal ions in the artificial waste of LFP batteries. This experiment was carried out by adding 2, 4, 6, 8, and 10 g of activated carbon, respectively, into 100 mL of an artificial waste solution then put into water-bath shaker at room temperature. For kinetic data, the filtrate was taken every 1 hour, while for equilibrium data the filtrate was taken every 24 hours. The concentrations of the initial solution and the filtrate were analyzed by ICP-OES. The experimental results showed the maximum percentage removal of lithium, calcium, sodium, and silica was at a dose of 100 g L-1 of activated carbon, which were 99.90%, 97.51%, 86.10%, and 79.08%, respectively. It was found that the Freundlich equilibrium model was more suitable for the adsorption isotherm indicated by the correlation coefficients value for lithium, calcium, sodium, and silicon were 0.9869, 0.8850, 0.8974, and 0.9576, respectively. This adsorption followed the Pseudo second order kinetic model derived from correlation coefficient values of chemical kinetic studies.

Efficient extraction of tungsten, calcium, and phosphorus from low-grade scheelite concentrate

• Scheelite and apatite in low-grade scheelite were digested completely by HNO 3 . • Tungsten was leached in the form of soluble phosphotungstic acid. • Calcium was leached and recovered in the form of gypsum whiskers. • The excess phosphorus can be recovered in the form of nitrophosphate fertilizer . In the traditional process for tungsten recovery from scheelite concentrate, phosphorus is regarded as a harmful impurity that should be strictly controlled. Moreover, the calcium that entered the resideue as Ca(OH) 2 or CaCO 3 was discarded or landfilled. To date, the residues from the traditional process have been listed as solid hazardous waste in China. A novel method was investigated to realize the comprehensive recovery of tungsten, phosphorus, and calcium. In the leaching process, 96% of scheelite (CaWO 4 ) and 99% of apatite (Ca 5 (PO 4 ) 3 F) were digested under the conditions of 3 M HNO 3 , at a liquid/solid ratio of 10:1, a leaching temperature of 90 °C, and leaching time of 2 h. After extracting tungsten from the leaching solution by solvent extraction, about 70% of Ca 2+ in the raffinate was recovered as calcium sulfate whiskers by adding H 2 SO 4 . Subsequently, the solution from the calcium removal process was reused to leach scheelite after adding the consumed HNO 3 . When the P 2 O 5 concentration in the circulating leaching solution was over 30%, it was discharged and neutralized by NH 3 ·H 2 O, and then used to produce a nitrophosphate fertilizer by spray granulation and drying processes.

The performance and mechanism of simultaneous removal of calcium and heavy metals by Ochrobactrum sp. GMC12 with the chia seed (Salvia hispanica) gum as a synergist

A bacterium Ochrobactrum sp. GMC12, capable of biomineralization and denitrification, was employed to investigate the performance and mechanism of heavy metals removal. A chia seeds (Salvia hispanica) gum was proposed as a synergist for the first time. The results showed that strain GMC12 reduced Ca2+, Cd2+, Zn2+, and nitrate by 83.38, 98.89, 98.95, and 100% (2.09, 0.29, 0.55, and 0.79 mg L−1 h−1), respectively, over 96 h continuous determination experiments. The concentration gradient test revealed that strain GMC12 would effectively remove Cd2+ and Zn2+ by 99.80 and 99.91% (0.67 and 1.35 mg L−1 h−1), respectively, under the synergistic effect of gum (1.0%, w/v). The SEM-EDS and XRD manifested that Ca2+, HMs ions, and anionic groups coated on the bacteria surface to form CaCO3, Ca5(PO4)3OH, CdCO3, Cd5(PO4)3OH, ZnCO3, and Zn2(PO4)OH. The fluorescence spectrometry and fourier transform infrared (FTIR) spectra illustrated that extracellular polymeric substance (EPS) was the key product for the nucleation site of bacteria, and the gum promoted the accumulation of bio-precipitates and accelerated the removal of HMs. In this research, Ochrobactrum sp. GMC12 exhibited great potential in wastewater treatment and chia seeds gum would go deep into material preparation and wastewater treatment due to its non-toxic nature, high viscosity, and advantageous morphology.

Microbial induced calcium precipitation based anaerobic immobilized biofilm reactor for fluoride, calcium, and nitrate removal from groundwater

In this study, the anaerobic quartz sand fixed biofilm reactor containing Cupriavidus sp. W12 was established to simultaneously remove calcium (Ca2+), fluoride (F−) and nitrate (NO3–N) from groundwater. After 84 days of continuous operation, the optimum operating parameters and defluoridation mechanism were explored, and the microbial community structure under different pH environments were compared and analyzed. Under the optimal operation conditions (HRT of 6 h, initial Ca2+ concentration of 180 mg L−1, and pH of 7.0), the removal efficiencies of Ca2+, F−, and NO3–N were 58.97%, 91.93%, and 100%, respectively. Gas chromatography (GC) results indicate that N2 is the main gas produced by the bioreactor. Three−dimension excitation emission matrix fluorescence spectroscopy (3D−EEM) showed that extracellular polymers (EPS) are produced during bacterial growth and metabolism. The results of Scanning electron microscopy−energy dispersive spectrometer (SEM−EDS), X−ray diffraction (XRD), and Fourier transform infrared spectrometer (FTIR) demonstrated that the defluoridation mechanism is attributed to the synergetic effects of ion exchange, co−precipitation, and chemisorption. The comparative analysis of the microbial community structure under different pH conditions show that Cupriavidus is the dominant bacteria in the bioreactor throughout the experiment, and it shows a prominent advantage at pH of 7.0. This research provides an application foundation for anaerobic microbial induced calcium precipitation (MICP) bioremediation of Ca2+, F−, and NO3–N from groundwater.

Mechanical Stress Modulates Calcium-Activated-Chloride Currents in Differentiating Lens Cells.

During accommodation, the lens changes focus by altering its shape following contraction and relaxation of the ciliary muscle. At the cellular level, these changes in shape may be accompanied by fluid flow in and out of individual lens cells. We tested the hypothesis that some of this flow might be directly modulated by pressure-activated channels. In particular, we used the whole cell patch clamp technique to test whether calcium-activated-chloride channels (CaCCs) expressed in differentiating lens cells are activated by mechanical stimulation. Our results show that mechanical stress, produced by focally perfusing the lens cell at a constant rate, caused a significant increase in a chloride current that could be fully reversed by stopping perfusion. The time course of activation and recovery from activation of the flow-induced current occurred rapidly over a time frame similar to that of accommodation. The flow-induced current could be inhibited by the TMEM16A specific CaCC blocker, Ani9, suggesting that the affected current was predominantly due to TMEM16A chloride channels. The mechanism of action of mechanical stress did not appear to involve calcium influx through other mechanosensitive ion channels since removal of calcium from the bath solution failed to block the flow-induced chloride current. In conclusion, our results suggest that CaCCs in the lens can be rapidly and reversibly modulated by mechanical stress, consistent with their participation in regulation of volume in this organ.

Synergistic removal of calcium and iron impurities from calcium-rich and high-alumina fly ash by acid leaching control

Fly ash is an ultrafine solid waste generated during coal combustion in industry, and the impurities contained significantly inhibit its high-value utilization. Based on a novel acid leaching control process to comprehensively utilize the high-alumina fly ash, the synergistic removal of calcium and iron impurities and the reaction mechanism was systemically studied. The removal property of CaO and Fe2O3 using hydrochloric acid solution is better than other acid solutions. Increasing the acid concentration, leaching temperature, duration and liquid-solid ratio can promote the removal efficiencies of CaO and Fe2O3, but excessive acid concentration and leaching temperature decrease the removal efficiencies. The optimal conditions for the synergistic removal of calcium and iron impurities are leaching at 80 °C for 2.0 h under a liquid-solid ratio of 4.0 in 6.0 mol·L−1 hydrochloric acid, and both the residual contents of CaO and Fe2O3 in the leached product are less than 0.7%. The reaction kinetics of calcium and iron impurities in hydrochloric acid solution correspond to the layer diffusion control, and the apparent activation energies are 44.04 kJ·mol−1 and 50.68 kJ·mol−1 respectively. The minerals of fly ash after treatment are mainly mullite, quartz and amorphous alumina, while the minerals of gehlenite, anhydrite and hematite dissolve in the leaching process.

Isolation and characterisation of micellar casein from buffalo milk using microfiltration technique with modified buffer composition

The objective of this work was to study the effect of di‐sodium phosphate (Na2HPO4) and calcium chloride (CaCl2) salt concentrations (10 to 90 mM) on the isolation of casein micelles from buffalo milk by microfiltration (0.20 μm) process. Destabilisation of buffalo micellar casein resulted in the presence of CaCl2. A complete isolation of caseins from buffalo skim milk was achieved using modified buffer containing 90 mM Na2HPO4 after 4th cycle of washing with 92% removal of whey proteins. Modification of casein micelles with Na2HPO4 resulted in 33% removal of calcium in the preparation of buffalo micellar casein. Based on transmission electron micrographs, no aggregation was recorded for buffalo micellar casein and size varied from 30 to 80 nm.

A mathematical estimation for quantified calcium supplementation during intermittent hemodialysis using regional citrate anticoagulation.

Regional citrate anticoagulation has been recommended as an alternative of anticoagulation for patients at high risk of bleeding undergoing intermittent hemodialysis. Precise calcium supplementation is important for the safety of regional citrate anticoagulation. In this study, we aimed to develop a possible method to optimize calcium supplementation for regional citrate anticoagulation in intermittent hemodialysis. The investigation consisted of a pilot study and a validation study. 18 patients undergoing intermittent hemodialysis anticoagulated by citrate, and six types of filters were included in the pilot study. The ionized calcium levels were monitored and maintained in the targeted range. Calcium-free dialysate was used in the study. After linear regression analysis of the clearance of non-protein bound calcium and calculating the ratio of the non-protein bound calcium concentration to total calcium concentration, we developed a mathematical model for estimation of extracorporeal circuit calcium removal. Another 8 maintenance hemodialysis patients (12 sessions) were enrolled in the validation study to validate the new version of the calcium supplementation approach. In the pilot study, positive correlations were found between the clearance of non-protein bound calcium and the hematocrit-adjusted clearance of creatinine and phosphate given in the dialyzer leaflet (R2 =0.31, p=0.0165). The ratio of the non-protein bound calcium concentration to total calcium concentration at the pre-filter point after infusion of citrate were constant about 0.75. In the validation study, we found that the systemic ionized calcium levels were stably maintained in the safe range and no filter clotting occurred during the hemodialysis when we used the new model of calcium supplementation. We developed a possible method to quantify calcium supplementation for intermittent hemodialysis anticoagulated by citrate which may help to avoid negative calcium balance and reduce the incidence of complications.

High-Efficiency Removal of Calcium and Magnesium from Lithium-Concentrated Solution via Counter-Current Extraction Using Di-(2-ethylhexyl)phosphinic Acid

A high loss ratio of lithium (Li+) and low removal efficiency of calcium (Ca2+) and magnesium (Mg2+) remain a major challenge so far in obtaining high-purity lithium products from a lithium-concentrated solution. In this work, a state-of-the-art separation and purification process including saponification, extraction, scrubbing, stripping, and precipitation was proposed, which achieved the ultrapurity lithium concentration. Compared with the previously reported di(2-ethylhexyl)phosphoric acid (P204, D2EHPA) system, the selected extractant di(2-ethylhexyl)phosphinic acid (P227) showed superior separation ability with a lower loss ratio of Li+. Meanwhile, the stripping acidity of the loaded organic phase was low, and the selective stripping of Li+ can be achieved by controlling the phase ratio. In the ternary mixed system, the removal efficiency of Ca2+ and Mg2+ reached 99.81% and 100%, respectively, while only 0.71% Li+ was extracted. The yield and purity of Li+ at an aqueous phase exit were 98.44% and 99.99%, respectively, indicating the successful production of the ultrapurity lithium-concentrated solution. Furthermore, in the simulated actual solutions, the 100% removal efficiencies of both Ca2+ and Mg2+ and only 2.09% Li+ loss demonstrated that our system possesses the potential of high-performance practical applications. More importantly, the high-purity Li2CO3 product was therefore obtained by precipitation treatments. These findings take a step toward developing an ultrahigh ion-selective technique for efficient lithium purification from a lithium-concentrated solution that could serve as industrially applicable separation platforms.

Removal of Calcium over Apricot Shell Derived Activated Carbon: Kinetic and thermodynamic study

The apricot shells (AS) derived activated carbon (AC) was employed in removing the water hardness ions (calcium) from synthetic hard water. The ZnCl2 activation route was implemented in synthesizing the AC from the AS. The typical AC sample was diagnosed for its morphology by the FESEM technique, elemental analysis using EDX technique, influential surface groups by FTIR spectroscopy, and crystallinity by the XRD. This AC sample was then applied to eliminate the calcium ion (Ca+2) from synthetic hard water by investigating factors affecting the Ca+2 removal efficiency, like the solution pH, Ca+2initial concentration, AC dosage, temperature, and contact time. The outcomes revealed that Ca+2 removal by the so-synthesized AC is pH, temperature, and time-dependent. The best Ca+2 removal % reached 80.12 %, while the best adsorption capacity was 70.42 mg/g. The Langmuir adsorption isotherm and the pseudo-second-order kinetic model demonstrated were best described Ca+2 removal by the AC. The enthalpy and Gibbs free energy functions indicated that Ca+2adsorption is endothermic and spontaneous. Thus, the consequences assured that the ASs derived AC can be exploited as an effective adsorbent to remove Ca+2from the solution.

Enhanced Removal of Fluoride, Nitrate, and Calcium Using Self-Assembled Fungus-Flexible Fiber Composite Microspheres Combined with Microbially Induced Calcium Precipitation

Enhanced Removal of Fluoride, Nitrate, and Calcium Using Self-Assembled Fungus-Flexible Fiber Composite Microspheres Combined with Microbially Induced Calcium Precipitation

Sphingosine-1-phosphate induces Ca<sup>2+</sup> mobilization via TRPC6 channels in SH-SY5Y cells and hippocampal neurons

Sphingosine-1-phosphate (S1P) is a widely expressed biologically active sphingolipid that plays an important role in cell differentiation, migration, proliferation, metabolism and apoptosis. S1P activates various signaling pathways, some of which evoke Ca<sup>2+</sup> signals in the cytosol. Few studies have focused on the mechanism by which S1P evokes Ca<sup>2+</sup> signals in neurons. Here, we show that S1P evokes global Ca<sup>2+</sup> signals in SH-SY5Y cells and hippocampal neurons. Removal of extracellular calcium largely abolished the S1P-induced increase in intracellular Ca<sup>2+</sup>, suggesting that the influx of extracellular Ca<sup>2+</sup> is the major contributor to this process. Moreover, we found that S1P-induced Ca<sup>2+</sup> mobilization is independent of G protein-coupled S1P receptors. The TRPC6 inhibitor SAR7334 suppressed S1P-induced calcium signals, indicating that the TRPC6 channel acts as the downstream effector of S1P. Using patch-clamp recording, we showed that S1P activates TRPC6 currents. Two Src tyrosine kinase inhibitors, Src-I1 and PP2, dramatically inhibited the activation of TRPC6 by S1P. Taken together, our data suggest that S1P activates TRPC6 channels in a Src-dependent way to induce Ca<sup>2+</sup> mobilization in SH-SY5Y cells and hippocampal neurons.

Calcium and silica removal from water in evaporative cooling systems, using precipitation and electrocoagulation

Calcium and silica removal from water in evaporative cooling systems, using precipitation and electrocoagulation

The Conversion of Calcium-Containing Phases and Their Separation with NaCl in Molten Salt Chlorinated Slags at High Temperature

The titanium resources in Panxi reign, China, have a high-impurities content of Ca and Mg, which is usually processed by the molten salt chlorination process. This process allows higher Ca and Mg content in its furnace burdens. However, there is a huge amount of molten salt chlorinated slag produced by this process, consisting of complex compounds and waste NaCl/KCl salts. These slags are always stockpiled without efficient utilization, causing serious environmental pollutions. To recycle the NaCl in the slag back to the molten salt chlorination process, a novel process to deal with those molten salt chlorinated slags with phase conversion at high temperature is presented in this paper. The calcium-containing solid phase was generated when Na2SiO3 was added to the molten salt chlorinated slags at high temperature, while NaCl was kept as a liquid. Thus, liquid NaCl was easily separated from the calcium-containing solid phase, and it could be reused in the molten salt chlorination process. The conversion of calcium-containing phases and their separation of NaCl are the key parts of this work, and they have been systematically studied in this paper; thermodynamic analysis, phase transformation behavior, and calcium removal behavior have all been investigated. The calcium removal rate is 78.69% when the molar ratio of CaCl2:Na2SiO3 is 1:1.5 at 1173 K and N2 atmosphere.