Wet Chlorination Research Articles

The extraction of tin (Sn) from primary tin ore deposits using wet chlorination

More than half of the world’s tin production is from secondary ore deposits. However, along with its depletion, PT Timah Tbk has explored and mined the primary deposits in Belitung, one that is expected to become tin’s new source. Tin was found liberated as cassiterite in the secondary deposits, while in the primary, it was associated with other minerals requiring more complex processing. Therefore, a suitable technology is needed to extract the tin from the primary ore deposits. This research aims to observe the extraction of tin from primary deposits (oxide and skarn ores) using HCl wet chlorination, observed at different temperature (60 – 90°C), HCl concentrations (10 – 50 % excess of stoichiometric amount), leaching time (60 – 300 minutes), and with or without the addition of oxidant (hydrogen peroxide, H2O2). The research found that the highest percentage of tin extraction from oxide and skarn ores was 92.32% and 97.28%, respectively. Both results were achieved at the same optimum condition: temperature of 60°C, 50% excess of HCl, 240 minutes of leaching time, and at two-fold excess of the stoichiometric amount of H2O2. It was concluded that oxidative wet chlorination could be used to recover tin from its primary ore deposits.

Experimental process analysis and mathematical modeling for selective gold leaching from slag through wet chlorination

The aim of this paper consists in defining optimal conditions of controlled and selective gold leaching contained in copper–gold slag, by wet chlorination. Studies were conducted on three types of copper–gold slag, resulting as by-products from pyrometallurgical processing of non-ferrous raw materials. Due to high levels of copper in slag, an oxidative pre-treatment is necessary to separate gold from accompanying elements and also for copper recovery. After nitric acid pre-treatment, nearly 87% of Cu was readily extracted, and lead and silver contents in all three types of solid samples have been reduced by 91.34% and 96.29%, respectively. Selective leaching of the solid phase resulting after HNO3 pre-treatment was done by wet chlorination, using nascent chlorine (Cl2) as the leaching agent, with the presence of hydrochloric acid (HCl). The chlorine was obtained “in situ” by the reaction of sodium hypochlorite (NaOCl, 5% Cl2) and HCl. In this study, the effect of nitric acid pre-treatment, redox potential (Eh) given by sodium hypochlorite (NaOCl) consumption, hydrochloric acid concentration, temperature and leaching time have been studied. The potential required for a rapid leaching rate and for avoiding the reduction of gold is 950mV (vs AgCl/Ag(KCl sat)). The 5% NaOCl consumption required for gold leaching from pre-treated samples was lower than NaOCl consumption necessary for original sample leaching. The highest gold extraction yield (98%) was obtained after 6h at ambient temperature, solid/liquid ratio (w/v) 1:2 and 4M HCl. In order to explain experimental results a mathematical model of the simultaneous gold, copper, lead and silver dissolution has been developed. It considers at particle level, the competition between surface reaction and the diffusion of the active species by a gel coating that covers the dissolving particle.

The Hydrometallurgical Extraction and Recovery of High-Purity Silver

With the continuous reduction in the availability of extractive metallurgical curricula in colleges and universities, the concern has in part been from where will the next generation of extractive metallurgists come? One objective of this article is to emphasize the fact that extractive metallurgy is, in fact, one of many areas of chemical engineering technology. Thus, although the extractive metallurgist may have disappeared in name, its activity is alive and well, subsumed in the field of chemical engineering. One goal of this lecture is to demonstrate the applicability of chemical engineering principles to what is typically considered “the field of extractive metallurgy.” Two processes will be described that have supplanted typical pyrometallurgical fire refining of precious metals, particularly silver. The origins of fire refining can be traced back to biblical times. There are numerous references to it in the old testament: Ezekiel 22:20, “As men gather silver and bronze and iron and lead and tin into a furnace to blow the fire upon it in order melt it”; Jeremiah 6:29, “The bellows blow fiercely; the lead is consumed by the fire; in vain the refining goes on”; and Malachi 3:2 (The Oxford Annotated Bible with the Apocrypha), “For he is like a refiners fire.” Many references to it will also be found in “De Re Metallurgica” and as well in Lazarus Ercker’s 1574 Manual “Treatise on Ores and Refining.” Today, fire refining has been improved greatly by innovative furnace design, new fluxing technologies, and the improved use of oxygen. However, fundamentally, the process chemistry has not changed much in the last millennium. Illustrations of hydrometallurgical processing of silver-bearing inputs will be provided by the treatment of sulfated silver-bearing materials and chlorinated slimes. The first of these technologies will be described briefly as practiced by the Phelps Dodge Refining Corporation for several years. The second, the treatment of silver chloride-bearing inputs, will be described in detail to demonstrate how typical chemical engineering unit process and unit operations have supplanted classic smelting and fire refining techniques. The Kennecott Copper Company, which has operated a hydrometallurgical circuit successfully for the recovery of high-purity silver from the slimes wet chlorination residue, has permitted me to provide some operation information and results using the technology. Both Phelps Dodge and Kennecott should be recognized for their forward-looking attitude in undertaking the conversion of conceptual chemistry into successful, full-scale plants. The process as employed at Phelps Dodge is discussed at length in reference (J.E. Hoffmann and B. Wesstrom: Hydrometallurgy, 1994, vol. 94, pp. 69–105).

Effects of Ultrasound Irradiation on Wet Wool Chlorination Treatment

In this study ultrasonic energy is applied for improving wet wool chlorination treatment one of the most well-established methods for reducing wool shrinking related to the felting. Sodium hypochlorite used for providing active chlorine in chlorination bath and samples chlorinated in the presence and absence of ultrasonic irradiation with equal processing parameters. The concentration of active chlorine during the treatment, shrinkage percentage, friction and some mechanical properties of treated samples determined and compared. Scanning Electron Microscope used for investigating the effects of different treatments on removal of wool scales. According to the results it was concluded that applying ultrasonic energy causes desirable mechanical and chemical effects in chlorination process. Cavitation phenomena causes more abrasion on wool surface especially on sharp places i.e., scales and the formation of hydrogen peroxide in ultrasonic bath managing the aggressive reaction of active chlorine on cuticle.

Sample Digestion Methods for the Determination of Traces of Precious Metals by Spectrometric Techniques

Recent advances in digestion methods used in the analysis of precious metal samples by spectrometric techniques are reviewed. The applicability of a fire assay, a wet acid treatment, chlorination and alkaline oxidizing fusion to a quantitative recovery of metals from various materials is discussed. Data on the precious metal contents obtained by using particular digestion methods as well as UV-VIS spectrophotometry, atomic absorption spectrometry, atomic emission spectrometry and inductively coupled plasma mass spectrometry in the examination of various samples are tabulated.

UV ozone modification of wool fibre surfaces

An ultraviolet (UV) ozone treatment has been used to oxidise the surfaces of batches of natural wool fibres. The changes in surface composition and chemistry induced by this treatment have been followed using X-ray photoelectron spectroscopy (XPS). Oxidation of surface di-sulphide sulphur to sulphonic acid groups (- SO 3 H) containing S 6+ is observed at levels of approximately 90% conversion. This is significantly higher than levels previously achieved using oxygen plasmas. The treatment also appears to cause reaction of the proteinaceous carbon, leading to an increase in carbon-oxygen, particularly carbonyl, functionality. The data presented indicate that the treatment used is capable of producing surface sulphur and carbon chemistry of the type usually obtained by wet chlorination.

Oxygen plasma modification of wool fibre surfaces

AbstractA range of oxygen plasma treatments has been used to modify the surfaces of woven and fibrous wool samples. The resulting chemistry and composition have been characterised using X‐ray photoelectron spectroscopy (XPS). The extent of oxidation of di‐sulphide bonds to sulphur (SVI), in the form of sulphonic acid groups (−SO3H), by the plasma is shown to be only about 20–30% compared to 100% using a conventional wet chlorination process. However, the plasma does appear to react with surface carbon of the protein structure, leading to an increase in carbon‐oxygen functionalities. Total levels of surface oxygen achieved using the plasma technique are similar to those from the wet process.

The wet chlorination of electrolytic refinery slimes

This article briefly describes the classical processes of dore furnacing and refining and identifies the major problems and costs associated with these methods. The process chemistry of the wet chlorination of slimes is then described, followed by an examination of the various unit processes employed to recover the metal values from slimes. Finally, a conceptual treatment of slimes is presented and compared to conventional processes.

Reactions of coal mineral matter during coal chlorination

Samples of a high-volatile bituminous coal were chlorinated with Cl 2 in various media. Two chlorination procedures were used: dry and wet chlorination. The wet method led to decreases in high and low temperature ash yields, while no significant changes in yield took place with the dry chlorination procedure. FT-i.r. spectroscopy and X-ray diffraction were used to identify inorganic species present in fresh and chlorinated coal samples. Chlorination transformed various minerals (especially carbonates) into chlorides. Soluble chlorides were lost by dissolution after the wet procedure. No such loss of inorganic constituents was observed for the dry chlorination treatment, but chlorides gave rise to sulphate and nitrate artefacts during subsequent low temperature ashing treatment.

Some Physical Effects of Acid Wet Chlorination on Wool Fibers in Relation to Its Use as a Shrinkproofing Treatment for Wool

In the shrinkproofing of wool, uniformity of treatment between fibers is desirable but difficult to achieve. Laboratory- scale experiments, treating fibers in effect individually, have been conducted to determine whether the considerable varia tion normally obtained is due to inherent differences between the fibers, or is simply the result of inhomogeneous exposure to the chlorinating solution. It is shown that, under such laboratory conditions, a high degree of uniformity can be attained, even with levels of treatment which cause very little damage to the wool. There is, therefore, no inherent variation between fibers which would prohibit uniform treatment, and it is worth while to attempt to improve the present process. The techniques used for examination of the fibers were: comparison of forces required to extend 15% in water before and after treatment; microscopy and micromanipulation; the Allwörden reaction; friction measurements by an improved capstan method; loss of weight in a blank dye-bath. The amount of chlorine reacting was estimated approximately from auxiliary experiments.

A Method of Isolation of a Cuticle Sheath from Wool Fibres

Previous work on the wool fibre has resulted in the isolation of two membranous components, viz. the epicuticle and the cortical cell membranes, and the postulation of the presence of a third membrane, viz. the subcutiole membrane, or endocuticle. The present work describes the isolation from the wool fibre of a cuticular sheath, which has been shown to consist of epicuticle and endocuticle. The method described employs oxidation with potassium dichromate followed by extraction with ammonia. The material resistant to this treatment was examined in the optical microscope, and its morphological significance was confirmed by electron‐microscopic studies of gold‐shadowed residues. Electron microscopy also revealed a fibrillar and microfibrillar structure of the endocuticle, thus explaining the grooved appearance of the surface of damaged wool fibres (e.g. after wet chlorination). The sulphur content of the dichromate‐ ammoniaresistant endocuticle (comprising at most 2% of the original wool) is shown to be appreciably higher than that of the complete wool fibre. This sulphur is shown to be present in the form of cystine, but the resistance of the cystine in the cuticular layer to dichromate oxidation is unexplained.

The Effect of Chlorine on Dyed Nylon

After dry chlorination of wool, the chlorine retained by the fibres is present as hydrochloric acid (i.e. is extractable by alkaline solutions); whilst with nylon it is shown that the chlorine is more strongly combined, so that it is not completely extracted by sodium carbonate solution but can be removed by sodium bisulphite solution. Generally, absorption of chlorine by nylon is attended by an increase in fluidity of the nylon in m-cresol and a corresponding decrease in tensile strength; the degree of absorption of chlorine appears to vary with the type of dye used. The presence of wool has a “buffering” action on the uptake of chlorine by nylon and hence tends to protect the nylon from excessive damage. Of the groups of dyes examined (chrome, level-dyeing and neutral-dyeing acid dyes, together with a few soluble acetate-rayon dyes and direct cotton dyes), the chrome dyes were satisfactory in their fastness to chlorination. The lighter shades of neutral-dyeing acid dyes were useless and the other dyeings occupied intermediate positions. All these dyes, with a few exceptions, have a slightly higher fastness to wet chlorination. The above observations are illustrated in detail by tabulated and graphed data, together with colorimetric data for a representative selection of the dyes before and after dry chlorination.