Sulfate electrolyte acidified

Table 2 Estimated conductivity of acidified and non-acidified copper sulfate electrolyte. Acidified solution contains 1.8 M H2SO4. Copper sulfate concentration is 0.25 M.

Conductivity data of various copper sulfate electrolytes acidified to different degrees with sulfuric acid is presented in Fig. 3. As noted, the copper sulfate concentration affects the conductivity only slightly and the major contribution comes from the acid. Interestingly, for the same acid concentration, the lower copper sulfate... 

Figure 4. Scanning electron micrograph for the deposit obtained from acidified zinc sulfate electrolyte (9) (0.77M Zn", 7M H2SOh) containing 40 ppb Sb, X 920...

Fig. 1 Schematic of a wafer plating cell depicting the current feed contact ring (right), and a numerical simulation5 of the initial current distribution (left), indicating about a 10 1 initial current density ratio between edge (344 mA/cm2) to center (33 mA/cm2) under the simulated conditions (acidified copper sulfate electrolyte).

Conductivity data for acidified copper sulfate electrolytes was analyzed by Hsueh and Newman8. Our data is consistently lower (by about 10%), but tracks the reported trend. 

Hydrogen peroxide was first made in 1818 by J. L. Thenard who acidified barium peroxide (p. 121) and then removed excess H2O by evaporation under reduced pressure. Later the compound was prepared by hydrolysis of peroxodisulfates obtained by electrolytic oxidation of acidified sulfate solutions at high current densities ... 

In the copper electrorefining process, fire refined copper or blister copper is cast to form the anodes and the cathode is either a reusable stainless steel sheet or a thin sheet of electro deposited copper which finally becomes a part of the refined cathode. The electrolyte is an acidified solution of copper sulfate. 

Densification is also influenced by the presence of supporting electrolyte. As shown in the last line of Table II, the relative densification in acidified cupric sulfate is less than that in binary cupric sulfate solution. In the case of the supported redox reaction, that is, in the presence of KOH or NaOH, the migration effect makes the density difference larger than that expected from overall reaction stoichiometry. 

Numerous methods for the synthesis of salicyl alcohol exist. These involve the reduction of salicylaldehyde or of salicylic acid and its derivatives. The alcohol can be prepared in almost theoretical yield by the reduction of salicylaldehyde with sodium amalgam, sodium borohydride, or lithium aluminum hydride by catalytic hydrogenation over platinum black or Raney nickel or by hydrogenation over platinum and ferrous chloride in alcohol. The electrolytic reduction of salicylaldehyde in sodium bicarbonate solution at a mercury cathode with carbon dioxide passed into the mixture also yields saligenin. It is formed by the electrolytic reduction at lead electrodes of salicylic acids in aqueous alcoholic solution or sodium salicylate in the presence of boric acid and sodium sulfate. Salicylamide in aqueous alcohol solution acidified with acetic acid is reduced to salicyl alcohol by sodium amalgam in 63% yield. Salicyl alcohol forms along with -hydroxybenzyl alcohol by the action of formaldehyde on phenol in the presence of sodium hydroxide or calcium oxide. High yields of salicyl alcohol from phenol and formaldehyde in the presence of a molar equivalent of ether additives have been reported (60). Phenyl metaborate prepared from phenol and boric acid yields salicyl alcohol after treatment with formaldehyde and hydrolysis (61). 

The impure copper is used as the anode and is typically lm square, 35-50 mm thick and 330 kg in weight. The cathode is a 1 mm thick sheet and weighs about 5 kg it is made from very pure copper. Because copper is itself involved in the electrolytic process, the copper cathode is known as an active electrode. The electrolyte is a solution of copper(n) sulfate (0.3 mol dm-3) acidified with a 2 mol dm-3 solution of sulfuric acid to help the solution conduct electricity (Figure 5.17). 

The use of brine as a solvent in the hydrometallurgical separation of lead from its ores was extensively studied by Lyon and Ralston (H8). Saturated sodium chloride solution and neutral ammonium acetate solutions were found to be good solvents for lead chloride and lead sulfate. Lead oxide and lead carbonate became soluble if the brine was first acidified with either sulfuric or hydrochloric acid. The dissolved lead was recovered electrolytically (S18). Marsden (M13) used this method in a process to recover lead from zinc plant residues. About 80% recovery of the lead was obtained by leaching at ambient temperature and the recovery of lead was increased to 98% when hydrochloric acid was added to the brine. 

Habashi and Torres-Acuna (H6) described a process that involved th direct recovery of copper and elemental sulfur by anodic dissolution o copper (I) sulfide (white metal). The white metal produced from th (jopper matte analyzed 77.85% Cu and 19.20% S. A closed vessel wa used to prevent the evaporation of the copper (II) sulfate acidified wit sulfuric acid electrolyte. The electrolysis was carried out at room tempera ture. The sulfur originally present in the white metal went into the slim as pure elemental sulfur. The elimination of the converting and polin, steps in the conventional copper smelting and refining process can b realized by use of this technique. 

Actual electrolyte compositions were measured b gravimetric analysis of total sulfur species present after oxidation with hydrogen peroxide. A sample of membrane material was weighed and then dissolved in water. The insoluble matrix materials were filtered and the filtrate treated with excess hydrogen peroxide which oxidizes all sulfur species to sulfate. It was assumed t t oidy sulfur in the form of sulfide was present in the membrane under run conditions. This solution was then acidified with hydrochloric acid to decompose the carbonate to carbon dioxide and water. The solution was then boiled to de-gas the mixture... 

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