Acid solutions, metal, phosphate, sulfur

Metal, Phosphate, Sulfur, Formate, and Ammonia Sources in Acid and Alkaline Solutions... 

Attempts to separate thorium and uranium from sulfuric acid solution of monazite by solvent extraction with TBP were unsuccessful because distribution coefficients of uranium and thorium from monazite solutions were too low, as these elements are complexed by phosphate ion. Development of extractants with higher distribution coefficients for these metals has made solvent extraction a practical process for recovering uranium and thorium from monazite sulfate solutions and from sulfuric acid solutions of other thorium ores. This section describes processes tested on a pilot-plant scale by Oak Ridge National Laboratory [C5]. 

A number of methods have been reported in the literature for improving the thermal stability of acrylic fibers. For example, impregnating wet-spun fibers in the gel state with salts of metals from group II in the periodic table of the elements [496] or sodium sulfide solution [487] have been reported. Also, dried fiber can be impregnated with sulfuric acid solutions of formamide [488], phosphates or borax [489], or organotin salts [490]. 

The strong interactions with metal ions extend to the use of metal-modified electrodes in electrocatalysis. Catalysis has been demonstrated with four systems. Chromium treatment results in as much as a 200 mV positive shift in the reduction peak for lO in acetate buffer This has been compared to the necessity for prior oxidation of the platinum electrode surface Ruthenium pretreatment of (SN), electrodes results in a catalytic current for the I / couple in phosphate buffer, pH 7.6. These electrodes also photoelectrochemically reduce protons to hydrogen at —0.05 V versus SCE in dilute sulfuric acid solution Molybdate treated electrodes have been used to electrochemically reduce acetylene at potentials of 1.5 V versus SCE in borate and hydroxide solutions. Iron treated electrodes show some ability to facilitate this reaction, but the rate is slower than with the molybdate treated electrodes... 

Pla.tinum, Platinum plating has found appHcation in the production of platinised titanium, niobium, or tantalum anodes which are used as insoluble anodes in many other plating solutions (see Metalanodes). Plating solutions were often based on platinum "P" salt, which is diamminedinitroplatiniim (IT). A dinitroplatinite sulfate—sulfuric acid bath has been used to plate direcdy onto titanium (129). This bath contains 5 g/L of the platinum salt, pH adjusted to 2.0 with sulfuric acid. The bath is operated at 40°C at 10—100 A/m. Other baths based on chloroplatinic acid have been used in both acid and alkaline formulations the acid bath uses 20 g/L of the platinum salt and 300 g/L hydrochloric acid at 65° C and 10—200 A/m. The alkaline bath uses 10 g/L of the platinum salt, 60 g/L of ammonium phosphate and ammonium hydroxide to give a pH of 2.5—9.0. The alkaline bath can be plated directly onto nickel-base alloys acid baths require a gold strike on most metals. 

A majority of soil extractions of inorganic constituents are carried out to determine the metal content of a soil sample. In these cases, it is common to use add extracting solutions. Dilute hydrochloric and sulfuric acids are most commonly used. Nitric acid is an oxidizer, so undesired oxidation can occur during the extraction process using this reagent. Phosphate is a natural... 

Calcium sulfate crystals were precipitated in a Continuous Mixed Suspension Mixed Product Removal (CMSMPR) crystallizer by mixing of calcium phosphate and sulfuric acid feed streams. The formed calcium sulfate hydrate (anhydrite, hemihydrate and dihydrate) mainly depends on the temperature and the solution composition. The uptake of cadmium and phosphate ions in these hydrates has been studied as a function of residence time and solution composition. In anhydrite, also the incorporation of other metal ions has been investigated. The uptake was found to be a function of both thermodynamics and kinetics. 

Chemically pure reagents were used. Cadmium was added as its sulfate salt in concentrations of about 50 ppm. Lanthanides were added as nitrates. For the experiments with other metal ions so-called "black acid from a Nissan-H process was used. In this acid a large number of metal ions were present. To achieve calcium sulfate precipitation two solutions, one consisting of calcium phosphate in phosphoric acid and the other of a phosphoric acid/sulfuric acid mixture, were fed simultaneously in the 1 liter MSMPR crystallizer. The power input by the turbine stirrer was 1 kW/m. The solid content was about 10%. Each experiment was conducted for at least 8 residence times to obtain a steady state. During the experiments lic iid and solid samples were taken for analysis by ICP (Inductively Coupled Plasma spectrometry, based on atomic emission) and/or INAA (Instrumental Neutron Activation Analysis). The solid samples were washed with saturated gypsum solution (3x) and with acetone (3x), and subsequently dried at 30 C. The details of the continuous crystallization experiments are given in ref. [5]. 

Barium hydroxide decomposes to barium oxide when heated to 800°C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkahne, undergoes neutrahzation reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double decomposition reaction when Ba(OH)2 aqueous solution is mixed with many solutions of other metal salts. 

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