Boron Removal via Formation of Magnesium Silicate Solids during Precipitative Softening

Precipitative softening is an option to remove silicon and boron from natural waters. Silicon was removed from hard waters by precipitative softening when the molar ratio of Mg:Si was less than 6:1 by the formation of an amorphous magnesium silicate. This solid had an apparent solubility product constant of 10?25.66 and was stoichiometrically similar to the mineral forsterite, Mg2SiO4. Boron removal was consistent with sorption to this amorphous magnesium silicate and could be roughly described by a Freundlich isotherm: Bsorb/Mg2SiO4(s) = 21×Bsol0.51.     

水氯镁石复盐法脱水工艺

用烧瓶蒸馏装置模拟固定床脱水设备,研究用苯胺盐酸盐作脱水剂的复盐法将水氯镁石(MgCl2.6H2O)脱水制备无水氯化镁(MgCl2)的过程,考察复盐配料比例、保护气含水浓度、热解温度、热解时间等因素对所制备无水氯化镁产品中氧化镁和水分含量的影响,优化用固定床脱水工艺条件。结果表明,完全脱水和脱苯胺盐酸盐的最佳温度和时间分别是300℃与25～30 min和320～350℃与10～20min。最佳配料摩尔比C6H5NH2.HCl∶MgCl2.6H2O为1.1∶1.0。在最佳条件下,可得到合格的无水氯化镁产品MgCl298%～98.6%,MgO 0.03%～0.38%,苯胺盐酸盐0.10%～0.12%,水分0.60%～0.81%。     

The effects of magnesium on hydroxyapatite formation in vitro from CaHPO4 and Ca4(PO4)2O at 37.4 degrees C

The effects of magnesium ion on the formation of calcium-deficient hydroxyapatite [Ca9HPO4(PO4)5OH, CDHAp] from CaHPO4 and Ca4(PO4)2O dissolution were investigated using two magnesium sources: Mg3(PO4)2 (chemical system 1) or MgCl2 . H2O (chemical system 2) solutions. Because chloroapatite does not form from aqueous solutions, the use of two magnesium sources facilitated the determination of magnesium's role during synthetic hydroxyapatite formation in vitro and possible related effects during biomineralization. Isothermal calorimetry determined the progress of reactions. Two peaks are observed as heat is evolved during the formation of CDHAp in water at 37.4 degrees C. The nucleation and growth of CDHAp are the corresponding mechanisms. Although the time for complete reaction and total heat-of-reaction DeltaHr remain constant, the height of the first peak is reduced as the concentration of magnesium ion approaches 4 mM in either chemical system. Magnesium does not substitute into CDHAp even though there are calcium vacancies available. Subsequent increases cause the remaining heat peak to broaden and the time required for complete reaction to approach 24 hours as the initial MgCl2 concentration reaches 100 mM. Supersaturation limits chemical system 1 to Mg3(PO4)2 concentrations below 10 mM. A MgCl2 concentration of 3.16 M precludes CDHAp from forming for over 3 months; rather newberyite, MgHPO4 . 3H2O, precipitates. The morphology and surface area of the CDHAp formed in 100 mM MgCl2 solution are comparable to those of CDHAp formed in water. The surface areas are approximately 80 m2/g. Magnesium concentrations below 4 mM only inhibit nucleation whereas those above 4 mM inhibit growth as well. Magnesium phosphate complexes are more inhibitory than magnesium chloride complexes. Increasing the liquid-to-solids ratio or agitation significantly increases the induction period before reaction initiates. Increasing the liquid-to-solids ratio increases the time span for growth whereas increasing agitation decreases the time span for growth. The large inhibitory effect of agitation suggests quiescent systems are more suitable for determining the kinetics of HAp formation. A magnesium inorganic chemical activity (alphaMg = gammaMg[Mg2+]) many times greater than that in biological fluids is required before inhibition of hydroxyapatite formation is realized.     

Selective Precipitation of Phosphate from Semiconductor Wastewater

Selective precipitation of phosphate from fluoride-containing wastewater was studied using magnesium salts. Wastewater sampled from a semiconductor manufacture was found to contain 936 mg/L of fluoride (F?), 640 mg/L of sulfate (SO42?), 118 mg/L of phosphate (PO43?), and 26.72 mg/L ammonium (NH4+). Magnesium chloride (MgCl2) was more effective than magnesium oxide (MgO) in inducing precipitation reactions between magnesium and phosphate. Effects of both molar ratio ([Mg2+]:[PO43?]) and pH were examined and experimental results were compared with those from equilibrium modeling by PHREEQC. A total of 41.72% of phosphate was removed and recovered when at molar ratio of 3:2 and pH of 10. Precipitation of phosphate increased with increasing molar ratio and 66.19% of phosphate was recovered when molar ratio was 3:1. Precipitation of phosphate increased as pH changed from 8 to 10. However, it decreased as pH increased from 10 to 12, probably because of competition between phosphate and hydroxyl (OH?) ions. Solid precipitates were characterized by field emission scanning electron microscope with energy dispersive spectrometer and X-ray diffraction. In accordance with theoretical modeling, it was found that the precipitate in pH range of 8–10 was predominantly bobierrite [Mg3(PO4)2.8H2O] and some amorphous precipitates. However, brucite [Mg(OH)2] precipitate would start to form when pH became higher than 10. Results showed that MgCl2 can be a selective precipitation reagent for phosphate removal from semiconductor wastewater since it does not form precipitate with fluoride, sulfate, and ammonium.     

NaCl-KCl-MgCl_2熔盐中的CaF_2溶解行为及其对液镁汇集的影响

采用XRD、气冷阴极等手段对CaF_2在NaCl-KCl-MgCl_2电解质体系中的溶解行为及其对液镁汇集状况进行研究。研究表明,CaF_2在NaCl-KCl-MgCl_2熔盐溶解行为表现为CaF_2与MgCl_2反应生成CaCl_2和MgF_2,且随着CaF_2含量的添加,体系氟离子和钙离子浓度逐渐升高,但氟离子增加量相当较慢;CaF_2对液镁汇集的影响表现为与电解质中的MgO结合生成Mg_2OFCl和Mg_2OF_2,降低MgO对液镁汇集的影响,镁在阴极呈现大颗粒的片状结构;随着CaF_2添加量的增加,NaCl-KCl-MgCl_2熔盐体系表面张力逐渐降低,主要受反应产物CaCl_2生成的影响。     

Hydraulic Conductivity and Leachate Characteristics of Stabilized Fly Ash

Disposal of fly ash on land amounts to sacrificing precious land space. Recycling of fly ash is one of the methods of solving the disposal problem. Stabilization of a low lime fly ash with lime and gypsum was studied through large scale tests on the stabilized material designed to simulate field recycling conditions as closely as possible, and found to be a very effective means to control hydraulic conductivity and leachate characteristics. The effects of moulding water content, lime content, gypsum content, curing period, and flow period on hydraulic conductivity, and on leachate of metals flowing out of the stabilized fly ash are reported herein. With proper proportioning of the mix, and adequate curing, the values of hydraulic conductivity on the order of 10?7 cm∕s were achieved. The concentrations of As, Cd, Cr, Cu, Fe, Hg, Mg, Ni, Pb, and Zn in the effluent emanating from the hydraulic conductivity specimens of mixes with higher proportions of lime or lime and gypsum were below threshold limits acceptable for contaminants flowing into ground water.     

Particulate and THM Precursor Removal with Ferric Chloride

Pilot-scale experiments were performed to investigate the effectiveness of enhanced coagulation in removing particles and trihalomethane (THM) precursors from two surface source waters: California State Project water and Colorado River water. The removal of suspended particles and natural organic matter at various ferric chloride doses and coagulation pHs was assessed through source water and filter effluent measurements of turbidity, particle count, UV254, TOC, and THM formation potential. Overall, it was found that optimal removal of particles and THM precursors by enhanced coagulation with ferric chloride is obtained at high coagulant doses (>16 mg∕L) and low pH conditions. Generally, turbidity removal is more efficient and head loss is more moderate at ambient pH compared with pH 5.5. Additionally, filter effluent particle counts were found to be consistent with residual turbidity data. The removal of THM precursors by enhanced coagulation is significantly enhanced at pH 5.5 compared with ambient pH. The reduction in THM formation potential is consistent with the trends observed for the THM precursor removal data (i.e., UV254 and TOC data). Furthermore, specific UV absorbance was used to estimate the proportion of humic substances in the raw waters. Enhanced coagulation was found to be less effective for the source water with the lower specific UV absorbance.     

Precipitative Removal of As, Ba, B, Cr, Sr, and V Using Sodium Carbonate

Sodium carbonate softening at pH 10.3 is a viable method of removing the inorganic contaminants arsenic, barium, chromium, strontium, and vanadium from drinking water sources. A broad survey revealed that removals varied widely and were dependent on solution composition. Median removals of As, Ba, Cr, Sr, and V were 24, 100, 92, 99, and 60%, respectively. Linear and nonlinear empirical models were fit for crudely estimating the removal of these contaminants in the presence of other elements that are typically removed in the softening process (i.e., calcium, magnesium, silicon, iron, and aluminum). Boron was removed to a much lesser extent (median removal 2%) indicating soda ash softening is not a promising treatment option for this purpose.     

用镁和石灰对铁水脱硫预处理的热力学

由热力学数据计算与MgS、MgO和镁蒸气平衡的铁水中的硫和氧的活度。在Mg和CaO同时喷入铁水时,镁的脱硫能力会增大。以氮作载气,它会与镁生成Mg3N2,但是Mg3N2在高温下也能参与脱硫和脱氧反应。     

Mass spectral fragmentation of 18-norsteroids and 12-oxo-20-hydroxysteroids

The free magnesium concentration in the axoplasm of the giant axon of the squid, Loligo pealei, was estimated by exploting the known sensitivity of the sodium pump to intracellular Mg2+ levels. The Mg-citrate buffer which, when injected into the axon, resulted in no change in sodium efflux was in equilibrium with a Mg2+ level of about 3--4 mM. Optimal [Mg2+] for the sodium pump is somewhat higher. Total magnesium content of axoplasm was 6.7 mmol/kg, and that of hemolymph was 44 mM. The rate coefficient for 28Mg efflux was about 2 X 10(-3) min-u for a 500-mum axon at 22-25degreesC, with a very high temperature coefficient (Q10=4-5). This efflux is inhibited 95% by injection of apyrase and 75% by removal of external sodium, and seems unaffected by membrane potential or potassium ions. Increased intracellular ADP levels do not affect Mg efflux nor its requirement for Na+/o, but extracellularl magnesium ions do. Activation of 28Mg efflux by Na+/o follows hyperbolic kinetics, with Mg2+/o reducing the affinity of the system for Na+/o. Lanthanum and D600 reversibly inhibit Mg efflux. In the absence of both Na+ and Mg2+, but not in their presence, removal of Ca2+ from the seawater vastly increased 28Mg efflux; this efflux was also strongly inhibited by lanthanum. A small (10(-14) mol cm-2) extra Mg efflux accompanies the conduction of an action potential.     

NaCl-KCl-CaCl_2熔盐体系中Mg~(2+)在Mo电极上的阴极过程

采用钼电极,在973K的温度下,研究了MgCl2在三元NaCl-KCl-CaCl2熔融氯化物混合物中的电化学行为。采用方波伏安法(SWV)、循环伏安法(CV)、计时电流法(CA)和计时电位法(CP)研究Mg~(2+)在钼电极上的反应过程。结果表明,Mg~(2+)在钼电极上发生一步还原反应(Mg~(2+)+2e=Mg),是由扩散控制的可逆反应,镁在钼电极上的成核过程是瞬时成核,这与半球核的形成和生长机制是一致的。通过CV、CP和CA在973K的不同方法计算的Mg~(2+)扩散系数分别为1.09×10-5、1.24×10-5和3.23×10-5 cm2/s。在给定电位下阴极沉积产物为金属镁。     

Removal of Antibiotics from Surface and Distilled Water in Conventional Water Treatment Processes

Conventional drinking water treatment processes were evaluated under typical water treatment plant conditions to determine their effectiveness in the removal of seven common antibiotics: carbadox, sulfachlorpyridazine, sulfadimethoxine, sulfamerazine, sulfamethazine, sulfathiazole, and trimethoprim. Experiments were conducted using synthetic solutions prepared by spiking both distilled/deionized water and Missouri River water with the studied compounds. Sorption on Calgon WPH powdered activated carbon, reverse osmosis, and oxidation with chlorine and ozone under typical plant conditions were all shown to be effective in removing the studied antibiotics. Conversely, coagulation/flocculation/sedimentation with alum and iron salts, excess lime/soda ash softening, ultraviolet irradiation at disinfection dosages, and ion exchange were all relatively ineffective methods of antibiotic removal. This study shows that the studied antibiotics could be effectively removed using processes already in use in many water treatment plants. Additional work is needed on by-product formation and the removal of other classes of antibiotics.     

Identification of members of the HSP30 small heat shock protein family and characterization of their developmental regulation in heat-shocked Xenopus laevis embryos

Uptakes of (28)Mg at 10 s were measured at 0.1 and 1mM MgCl(2), to mainly represent one or other of the two uptake mechanisms earlier shown to be present in rat jejunal brush border membrane vesicles, one with an apparent KT of 0.2 mM, the other in the millimolar range. Both mechanisms had an optimal temperature close to 28 degrees C, inactivation at 37 degrees C being more acute for the low affinity mechanism (55 percent, P < 0.01). Both mechanisms were equally stimulated by an electrical potential difference (negative inside the vesicles) imposed by a potassium gradient and not affected by the nature of the anion accompanying magnesium. At 0.1 mM MgCl(2), the uptake was increased by an outwardly directed proton gradient, pH 8.2 outside and 7.4 inside (38 percent, P < 0.05), but not depressed when the gradient was in the opposite direction, pH 6.6 outside and 7.4 inside. It was trans-stimulated by magnesium, strongly inhibited by amiloride and to a smaller extent by furosemide, but uninfluenced by 0.1 mM NaCl or by 100 mM NaCl, NaSCN or KCl. A slight but significant inhibition (20-30 per cent) was recorded in the presence of 0.1 mM CoCl(2), NlCl(2) or BaCl(2). At 1 mM MgCl(2), the uptake was not influenced by pH gradient, was not trans-stimulated by Mg and was not affected by furosemide. A 40 percent inhibition by amiloride was, however, recorded. Also 100 mM NaCl or KCl doubled the uptake, while 1 mM NaCl or 100 mM NaSCN did not affect it. In contrast, all the divalent cations tested produced an inhibition (from 60 to 12 percent) in the following order: Co > or = Mn > Ca > or = Ni> Ba > Sr, when used at the same concentration as magnesium. The results showed that cobalt and calcium were not true competitors. In conclusion, two distinct mechanisms would operate magnesium entry at the brush border: (1) an electrogenic high affinity Mg/Mg,H exchange, sensitive to amiloride and furosemide, and (2) an electrogenic low affinity mechanism, inhibited by the presence of several divalent cations and dependent on the presence or activity of alkaline phosphatase.     

Synthetic Musk Fragrances in a Conventional Drinking Water Treatment Plant with Lime Softening

Synthetic musk fragrances are common personal care product additives and wastewater contaminants that are routinely detected in the environment. This study examines the presence of eight synthetic musk fragrances [7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN), 1,3,4,6,7,8-hexahydro-4,6,6,7,8-hexamethylcyclopenta-γ-2-benzopyran (HHCB), 5-acetyl-1,1,2,6-tetramethyl-3-iso-propylindane (ATII), 4-acetyl-1,1-dimethyl-6-tert-butylindane (ADBI), 6-acetyl-1,1,2,3,3,5-hexamethylindane (AHMI), 6,7-dihydro-1,1,2,3,3,-pentamethyl-4-(5H)-indanone (DPMI), 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene (musk xylene), and 4-tert-butyl-3,5-dinitro-2,6-dimethylacetophenone (musk ketone)] in source water and the removal of these compounds as they flow through a Midwestern conventional drinking water plant with lime softening. The compounds were measured in water, waste sludge, and air throughout the plant. HHCB and AHTN were detected in 100% of the samples and at the highest concentrations. A mass balance on HHCB and AHTN was performed under warm and cold weather conditions. The total removal efficiency for HHCB and AHTN, which averaged between 67–89%, is dominated by adsorption to water softener sludge and its consequent removal by sludge wasting and media filtration. Volatilization, chlorine disinfection, and the disposal of backwash water play a minor role in the removal of both compounds. As a result of inefficient overall removal, HHCB and AHTN are a constant presence at low levels in finished drinking water.     

Bacteriophage T7 DNA helicase binds dTTP, forms hexamers, and binds DNA in the absence of Mg2+. The presence of dTTP is sufficient for hexamer formation and DNA binding

The role of Mg2+ in dTTP hydrolysis, dTTP binding, hexamer formation, and DNA binding was studied in bacteriophage T7 DNA helicase (4A' protein). The steady state kcat for the dTTPase activity was 200-300-fold lower in the absence of MgCl2, but the Km was only slightly affected. Direct dTTP binding experiments showed that the Kd of dTTP was unaffected, but the stoichiometry of dTTP binding was different in the absence of Mg2+. Two dTTPs were found to bind tightly in the absence of Mg2+ in contrast to three to four in the presence of Mg2+. In the presence of DNA there was little difference in the stoichiometry of dTTP binding to 4A'. These results indicate that Mg2+ is not necessary for dTTP binding, but Mg2+ is required for optimal hydrolysis of dTTP. Gel filtration of 4A' in the presence of dTTP without Mg2+ showed that Mg2+ was not necessary, and dTTP was sufficient for hexamer formation. The hexamers formed in the presence of dTTP without Mg2+ were capable of binding single-stranded DNA. However, the 4A' hexamers formed in the presence of dTDP with or without Mg2+ did not bind DNA, indicating that hexamer formation itself is not sufficient for DNA binding. The hexamers need to be in the correct conformation, in this case in the dTTP-bound state, to interact with the DNA. Thus, the gamma-phosphate of dTTP plays an important role in causing a conformational change in the protein that leads to stable interactions of 4A' with the DNA.     

Mineralization and Biodegradability Enhancement of Low Level p-Nitrophenol in Water Using Fenton’s Reagent

This study presents the use of dissolved organic carbon (DOC) and biodegradable dissolved organic carbon (BDOC) to indicate the degree of mineralization and biodegradability (BDOC/DOC) change of a dilute p-nitrophenol aqueous solution (initial DOC of 8.5 MG/L) induced by Fenton’s reagent. Fe2+:H2O2:DOC ratios of 1:10:1, 10:10:1, and 10:100:1 and pH of 2, 3, and 4 were tested. Mineralization of p-nitrophenol of 5–35% was observed along with biodegradability increase. The best conditions for maximum mineralization were Fe2+:H2O2:DOC of 10:10:1 and pH of 4 while the optimum conditions for highest biodegradability increase were Fe2+:H2O2:DOC of 10:10:1 and pH of 3. Under the optimal conditions, the biodegradability was enhanced from 8 to 80%. More than 95% of total DOC removal and BDOC formation was observed in the first 10 min of the reaction. Results further indicated that Fe2+:H2O2:DOC of 10:10:1 and pH of 4 were optimal for a combination of the maximum DOC elimination and biodegradability increase.     

宝钢含锌粉尘用于转炉前期化渣的工艺实践

对宝钢含锌尘泥的厂内循环利用进行了研究，将含锌尘泥用于改善转炉前期造渣的试验表明，促进了石灰溶解，改善了前期化渣，提高了脱硫率，LT压块和矿石的耗量减少。造渣剂加入未引起钢水的明显增硫，对钢水和炉渣成分没有影响。     

Electrochemical formation of Mg-Li-Y alloys by co-deposition of magnesium, lithium and yttrium ions in molten chlorides

An electrochemical approach for the preparation of Mg-Li-Y alloys via co-reduction of Mg, Li, and Y on a molybdenum electrode in LiCl-KCl-MgCl2-YCl3 melts at 943 K was investigated. Cyclic voltammograms (CVs) illuminated that the underpotential deposition (UPD) of yttrium on pre-deposited magnesium led to the formation of a liquid Mg-Y alloy, and the succeeding underpotential deposition of lithium on pre-deposited Mg-Y led to the formation of a liquid Mg-Li-Y alloy. Chronopotentiometry measurements indicated that the order of electrode reactions was as follows: discharge of Mg(II) to Mg-metal, electroreduction of Y on the surface of Mg with formation of ε-Mg24+xY5 and after that the discharge of Li+ with the deposition of Mg-Li-Y alloys. X-ray diffraction (XRD) indicated that Mg-Li-Y alloys with different phases were formed via galvanostatic electrolysis. The microstructure of different phases of Mg-Li-Y alloys was characterized by optical microscope (OM) and scanning electron microscopy (SEM). The analysis results of inductively coupled plasma atomic emission spectrometer (ICP-AES) showed that the chemical compositions of Mg-Li-Y alloys corresponded with the phase structures of the XRD patterns, and the lithium and yttrium contents of Mg-Li-Y alloys depended on the concentrations of MgCl2 and YCl3 .     

In-Place Stabilization of Pond Ash Deposits by Hydrated Lime Columns

Abandoned coal ash ponds cover up vast stretches of precious land and cause environmental problems. Application of suitable in situ stabilization methods may bring about improvement in the geotechnical properties of the ash deposit as a whole, converting it to a usable site. In this study, a technique of in-place stabilization by hydrated lime columns was applied to large-scale laboratory models of ash ponds. Samples collected from different radial distances and different depths of the ash deposit were tested to study the improvements in the water content, dry density, particle size distribution, unconfined compressive strength, pH, hydraulic conductivity, and leachate characteristics over a period of one year. The in-place stabilization by lime column technique has been found effective in increasing the unconfined compressive strength and reducing hydraulic conductivity of pond ash deposits in addition to modifying other geotechnical parameters. The method has also proved to be useful in reducing the contamination potential of the ash leachates, thus mitigating the adverse environmental effects of ash deposits.     

Expression of androgen receptors in astrocytoma

This study determines ash, K, Ca, Na, Mg, Fe, Cu, Pb, and Zn content in musts and wines of the DOC Tacoronte-Acentejo (Tenerife, Canary Islands) from two consecutive harvests. Samples were treated with HNO3 and H2O2. Na and K were determined by flame photometry and the remaining metals by air/acetilene flame atomic absorption spectrophotometry. Significant differences were observed in Na, Ca and Mg contents between both harvests, possibly due to climate conditions.