表面活性剂影响Mg（OH）2吸附硼的研究

本文研究了表面活性剂对氢氧化镁吸附硼的影响,对不同类型的表面活性剂,不同的加入方式以及不同的加入量等进行了试验,并试验了在表面活性剂存在下,pH值对吸硼量的影响。阴离子表面活性剂——十二烷基硫酸钠的加入 可以减少Mg(OH)_2对硼的吸附;十二烷基硫酸钠加入的顺序对Mg(OH)_2吸硼没有影响,这表明Mg(OH)_2吸硼是可逆的;在十二烷基硫酸钠的存在下,最大吸硼量时的pH为10.3。     

联合法制取低硼海水镁砂的研究

降低海水镁砂中硼的含量有许多方法,例如碱洗法、过碱法、吸附法和选择性吸硼树脂法等。我们先采用吸附法制得低硼海水(含B_2O_33ppm),再用改良过碱法进一步降低硼含量,可制得含B_2O_3为0.01—0.02%的低硼海水镁砂。比较结果,联合法降硼比单一法降硼优越。 用Mg(OH)_2作吸附剂,吸硼后变为含硼沉淀,经过碱洗脱硼后,可循环使用。     

固体吸附剂吸硼研究概况

Ⅰ.硼的存在形式及去硼意义 据文献报道自来水中硼的含量为7×10~(-9)～0.2×10~(-6)g/L,海水中的含量为5×10~(-6)g/L,河水中的含量为13×10~(-6)g/L,地下水和卤水中的含量随各地而有所不同。在一般的水溶液中,硼以H_3BO_3,B(OH)_4~(-)形式存在,以H_3BO_3为主。硼酸是一元弱酸,是一种路     

海水的缓冲性能及缓冲容量

海水pH值的变化范围通常为7.5—8.6之间。其pH值变化范围之所以如此狭小,是因为海水是一种缓冲体系,具有一定的缓冲能力。 海水中可起缓冲作用的成份主要为二氧化碳体系(CO_2-HCO_3~--CO_3~(2-)),其次是B(OH)_3-B(OH)_4~-,HPO_4~(2-)-H_2PO_4~-,H_4SiO_4-H_3SiO_4~-等弱酸及其盐。但因这些成分浓度较低,缓冲能力也就较二氧化碳体系低得多,故在计算海水的缓冲容量时常忽略不计。 海水的pH值主要受二氧化碳系统的控制,而后者     

海水中铀在水合氧化钛上的吸附机理

随着海水提铀研究工作的开展,海水提铀的机理问题普遍地受到了重视。这一问题虽在十年前即被提出,但至今还没有解决。英国Davies、Keen等认为海水中的铀以UO_2~(+2)的形式吸附在水合氧化钛上面,吸附的方式为阳离子交换。而日本的尾方昇则认为是阴离子UO_2(CO_3)_3~(-4)配位吸附,但后来又说:“在海水pH范围内阳离子交换性较强”。1975年,本文作者曾提出为化学吸附,被吸附的是UO_2(OH)_3~-。张正斌等提出了新的论据,认为是阳离子交换,同时还指出,或许可以用“脱水络合”机理来阐明。此外,还有人主张用阴离子交换等等。意见很不一致,论据也不尽相同。 这里根据一些现有的实验,对海水中铀在水合氧化钛上的吸附机理作一初步探讨。     

海洋生物碳酸盐δ~(11)B-pH技术影响因素

20世纪90年代以来,利用海洋生物碳酸盐的硼同位素组成重建古海水pH的δ11B-pH技术已成为国际同位素地球化学研究的热点。虽然该技术取得了很多的研究成果,但由于理论上的不完善,使该技术中存在一些尚未解决的问题,限制了该技术的近一步应用。综合近些年来的研究成果,对δ11B-pH技术中的不确定因素:海水B(OH)3的电离常数pKa、海水的δ11Bsw值、海水中B(OH)4-的δ11B值和海水B(OH)4-与B(OH)3间的分馏系数α进行了详细研究,提出了该技术今后研究的方向,为更好地利用海洋生物碳酸盐的硼同位素组成研究古海洋环境提供参考。     

氢氧化铝-氢氧化铁复合吸附剂对海水吸铀量的研究

本文研究了制备Al(OH)_3-Fe(OH)_3复合吸附剂的最佳条件,在常温和一定浓度下吸附剂沉淀终点pH值的选择,以及在同样条件下纯Al(OH)_3纯Fe(OH)_3、与Al(OH)_3-Fe(OH)_3复合吸附剂对海水中吸铀量的比较。这种吸附剂的吸铀量已达到459μg/g,接近同样条件(40—60目通海水15天)下,以TiCl_4为原料制得的TiO_2吸附剂的最高吸附量。     

海水溶解氧基本测量转换器

1 海水溶解氧测定方法1.1 经典温克勒滴定法具体做法是在海水样品中加入少量MnCl_2和KOH溶液,其反应原理为:MnCl_2+2KOH2KCl+Mn(OH)_2↓白色Mn(OH)_2沉淀迅速被溶液中的溶解氧氧化,生成褐色沉淀Mn(OH)_3即: 4Mn(OH)_2+O_2+2H_2O=4Mn(OH)_3↓褐色Mn(OH)_3用硫酸或盐酸溶解即:     

南极洲赖特谷万达盐湖中铬的垂直迁移

南极洲万达湖湖水上部为氧化环境,铬浓度较低,Cr~(6+)占主导地位,主要以CrO_4~(2-)形式存在;下部为还原环境,铬浓度高,Cr~(3+)为主,以Cr(OH)_2~+和Cr(OH)~(2+)形式存在。湖水中锰、铁的氧化物及氢氧化物颗粒对铬离子的吸附和释放过程,控制了湖水铬浓度的变化。     

Fe（OH）3胶体与铜离子作用的研究

使用切向流超滤系统得到粒度较均匀的Fe(OH)3胶体,进而对Fe(OH)3胶体粒子与Cu2+的作用进行了研究,并将实验结果与南沙群岛海区表层水中铜与胶体物质结合状况的调查数据进行了比较分析,得到如下结果(1)在海水介质中,铜在Fe(OH)3胶体上结合的百分率(pH>5)随pH的升高而下降,随着Fe(OH)3胶体浓度的减小而下降.(2)在天然海水介质中,使铜在Fe(OH)3胶体上结合的百分率在50%-70%的有机物浓度为1.0mg     

ADSORPTION ACTION OF BASIC ZINC CARBONATE ADSORBENT ON URANIUM IN NATURAL SEAWATER

1. The adsorption action of basic zinc carbonate adsorbent on uranium in natural seawater can be expressed with the following formula of adsorption isotherm:C=k(U*)n = 8.51× 10-1(U*)0.49,where C is the concentration of uranium on adsorbent; U* is content of uranium in natural seawater employed.2. when the quantity of basic zinc carbonate adsorbent (T) is constant, with the increase of natural seawater quantity through the adsorption column (G), also increased are the adsorption content of uranium of the adsorbent (U), the concentration of uranium on the adsorbent (C) and the concentration of residual uranium (C0*) in natural seawater after adsorbing uranium, while the rate of recovery of uranium (R) is decreased. With the increase of (G) the coefficient of distribution (Kd) decreases to a certain value and then a little rises again.     

海水中微量元素无机离子交换动力学研究 Ⅳ.海水中铀(Ⅵ)与水合氧化钛离子交换反应的级数和活化能的测定

关于海水中铀(Ⅵ)与水合氧化钛的作用、国内外已有许多报导,内容包括水合氧化钛制备方法的不同对交换铀量的影响,水合氧化钛和海水中铀的基本物理—化学性质的研究及它们在反应过程中物理—化学性质变化规律的研究,海水中铀与水合氧化钛作用机理的研究等等。但对这一反应的动力学研究文献上报导极少,除了在本研究Ⅰ、Ⅱ和Ⅲ中报导的反应机理的研究[1,2]证明反应过程的速率由液膜扩散所控制之外,关于这一离子交换过程的反应级数和活化能的研究却至今未见有文献报导。     

水合氧化锆吸附硼的研究

详细地研究了硼在水合氧化锆吸附剂上的吸附行为。研究结果表明，水合氧化锆的吸硼速率较快，２ｈ可完全达平衡，且吸附可用Ｆｒｅｕｎｄｌｉｃｈ等温吸附线很好地拟合。被吸附的硼易被碱液洗脱，通过水合氧化锆上硼的“吸附－脱附循环”研究，表明该吸附剂的吸附性能好，再生能力强，循环使用寿命长，是一种很有价值的高效脱硼吸附剂。     

Aluminum hydroxide’s solubility and the forms of dissolved aluminum’s occurrence in seawater

The solubility of aluminum hydroxide in seawater of 35‰ salinity at pH = 7.4−8.2 and 25°C was determined experimentally for three samples synthesized in different ways. The solubilities of two phases subjected to ageing and precipitated (a) from a boiling solution of aluminum sulfate and (b) immediately from seawater at room temperature were a little different and showed the minimum within pH = 8.05−8.10. The solubility of aluminum hydroxide precipitated from a solution of sulfate aluminum at room temperature and not subjected to ageing was about twofold at pH∼7.9. The analysis of the pH dependence of the concentration of dissolved aluminum allows one to suppose that an Al(OH)₂⁺ hydroxo complex is the primary form of the aluminum occurrence in seawater at pH < 8.05, whereas the Al(OH)₄⁻ anion is prevailing at pH > 8.10. Electrically neutral Al(OH)₃⁰ hydroxocomplexes may be prevailing within the narrow range of pH = 8.05−8.10 and, in general, are of secondary importance.     

Boron isotopic fractionation during seawater evaporation

Laboratory experiments were undertaken to investigate the behaviour of boron at the seawater–air interface during seawater evaporation. Seawaters adjusted to different pH values were heated to 27, 33 and 40 °C inside a quartz evaporator. The vapor was collected with a quartz condenser using a cold trap. A natural seawater–vapor process in quiet air conditions and excluding the sea-spray component was realized using this arrangement. The results indicate an enrichment of ¹¹B in the condensate. This implies that in the natural environment, rainfall with δ¹¹B values lower than that of seawater has been affected either by continental boron sources or by the boron extracted from seawater under airflow conditions. While the net flux of boron carried away from the ocean by air masses due to seawater evaporation is significant compared to other fractionation-associated processes removing boron from the ocean, the effect of isotopic fractionation as boron enters the vapor phase on the isotopic composition of boron in the ocean over time is small.     

Behaviour of boron,calcium and magnesium in a polluted estuary

Behaviour of industrially added boron in the well mixed Ambika river estuary of South Gujarat, India has been studied along with that of calcium and magnesium. The ratios of Ca : Cl and Mg : Cl at varying chlorinities were always within the normal ranges found in river water at one end and seawater at the other end. B : Cl exceeded the river water end limit at the ebb tide at an upstream station. Percentage addition or removal of boron, calcium and magnesium was calculated using the concept of the theoretical dilution line. The external input raised the boron concentration by 263% in the vicinity of the industrial discharge. A correlation coefficient of ?0·82 between chlorinity and percentage addition or removal of boron supports the theory of boron incorporation in sediments in amounts proportional to salinity. Inverse relationship between percentage addition or removal of boron and suspended solids was observed. Behaviour of calcium and magnesium was in line with the replacement of Ca²⁺ ions occupying the majority of ion-exchange sites in riverine clays by Mg²⁺, Na⁺ and K⁺ during their first encounter with seawater.     

Impact of environmental factors on in situ determination of iron in seawater by flow injection analysis

A sensitive method for iron determination in seawater has been adapted on a submersible chemical analyser for in situ measurements. The technique is based on flow injection analysis (FIA) coupled with spectrophotometric detection. When direct injection of seawater was used, the detection limit was 1.6 nM, and the precision 7%, for a triplicate injection of a 4 nM standard. At low iron concentrations, on line preconcentration using a column filled with 8-hydroxyquinoline (8HQ) resin was used. The detection limit was 0.15 nM (time of preconcentration = 240 s), and the precision 6%, for a triplicate determination of a 1 nM standard, allowing the determination of Fe in most of the oceanic regimes, except the most depleted surface waters. The effect of temperature, pressure, salinity, copper, manganese, and iron speciation on the response of the analyser was investigated. The slope of the calibration curves followed a linear relation as a function of pressure (C_p = 2.8 × 10^{− 5}P + 3.4 × 10^{− 2} s nmol^{− 1}, R² = 0.997, for Θ = 13 °C) and an exponential relation as a function of temperature (C_Θ = 0.009e^0.103Θ, R² = 0.832, for P = 3 bar). No statistical difference at 95% confidence level was observed for samples of different salinities (S = 0, 20, 35). Only very high concentration of copper (1000 × [Fe]) produced a detectable interference. The chemical analyser was deployed in the coastal environment of the Bay of Brest to investigate the effect of iron speciation on the response of the analyser. Direct injection was used and seawater samples were acidified on line for 80 s. Dissolved iron (DFe, filtered seawater (0.4 μm), acidified and stored at pH 1.8) corresponded to 29 ± 4% of Fe_a (unfiltered seawater, acidified in line at pH 1.8 for 80 s). Most of Fe_a (71 ± 4%) was probably a fraction of total dissolvable iron (TDFe, unfiltered seawater, acidified and stored at pH 1.8).     

A theoretical study of the kinetics of the boric acid–borate equilibrium in seawater

Dissolved boron in seawater occurs mainly in the form of boric acid (B(OH)₃) and borate (B(OH)₄⁻). While the equilibrium properties of the dissociation of boric acid have been studied in detail, very little work has focused on the kinetics of the boric acid–borate equilibrium in seawater. Here, we present a theoretical study of the relaxation of the seawater borate–carbonate system towards equilibrium using the experimental data of Mallo et al. [Nouv. J. Chim. 8 (1984) 373] and Waton et al. [J. Phys. Chem. 88 (1984) 3301]. The reaction rate constants are two to four orders of magnitude smaller than typical rate constants of diffusion-controlled reactions of other acid–base equilibria. This is presumably due to the substantial structural change that is involved in the conversion from planar B(OH)₃ to tetrahedral B(OH)₄. The time required to establish the boric acid–borate equilibrium in seawater is calculated to be ∼95μs at temperature T=25°C and salinity S=35. Considering stable boron isotopes ¹¹B and ¹⁰B, the isotopic equilibration time is ∼125 μs. As a result, kinetic isotope effects during coprecipitation of boron in calcium carbonate are unlikely and therefore do not affect the use of stable boron isotopes as a paleo-pH recorder.     

Quantitative adsorption of organic matter from seawater on solid matrices

The influence of several operational parameters, including pH, flow rate, total volume of water passed, and choice of eluants, upon the efficiency of extraction of organic matter from seawater by two forms of commercially-available resin, XAD-2 and XAD-8, is considered. The overall efficiency of adsorption is at best 40%. The main factor determining the adsorption efficiency of XAD resin for natural organic matter is pH. The efficiency at normal seawater pH is only half that at pH 2.0. Although the efficiency decreases with increasing flow rate, the decrease is not great up to 3 bed vol./min. With increasing volume of water passed, the adsorption capacity of the resin initially drops, but reaches an approximately constant level after 1000 bed volumes. Alkaline solutions, either NH₄OH or NaOH, followed by methanol, completely recover adsorbed organic material from the resin. There is no significant advantage of XAD-8 over XAD-2 for seawater extractions, and the materials adsorbed by the two forms of resin are not substantially different.A new separation method combining XAD-2 resin and activated carbon as adsorbents in series in a column has been developed. Efficiencies of up to 90% were obtained in the extraction of acidified seawater. When the volume of water passed was less than 500 bed volumes, the adsorption as measured by UV-oxidation was quantitative. Elution of 90–100% of the adsorbed organic carbon was possible when ammonium hydroxide (7 M), methanol and an ammonium hydroxide—methanol mixture were used sequentially.