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Author: John Holroyd Publisher: ISBN: Category : Electroplating Languages : en Pages : 71
Book Description
Bench scale experimentation was initiated to evaluate the solubilities and sludge characteristics associated with selected heavy metals and their hydroxides for both homogeneous and heterogeneous solutions. Data suggests that in a mixed-metal solution, mixed-metal co-precipitants form and the point of zero charge (PZC) for these precipitants depends upon the specific metal content of the colloidal precipitants. In general the presence of chromium (III) depresses the overall PZC while nickel and cadmium, when major waste components, tend to raise the PZC. Aging was found to impact chromium hydroxide dewatering but it is not clear that the theoretical aspects of aging chemistry can be used to predict changes. High molecular weight anionic polymers were effective in conditioning metal sludges with respect to cake formation/filtrate clarity but help dewatering rates very little. Previously developed relationships for inorganic sludges which allowed predictions about sand bed, centrifugation, and vacuum filtration dewatering processes based on gravity thickening data were found to hold for metal sludges. Based on these relationships and the laboratory data gathered here it is concluded that vacuum filtration is the only reasonable process to insure a handleable sludge. If direct reclamation of the metals from the mixed hydroxide slurry is to be attempted centrifugation may be employed. Based on a literature review and a basic economic evaluation, liquid/liquid extraction was recommended for further study as the metal recovery process of choice. (Author).
Author: John Holroyd Publisher: ISBN: Category : Electroplating Languages : en Pages : 71
Book Description
Bench scale experimentation was initiated to evaluate the solubilities and sludge characteristics associated with selected heavy metals and their hydroxides for both homogeneous and heterogeneous solutions. Data suggests that in a mixed-metal solution, mixed-metal co-precipitants form and the point of zero charge (PZC) for these precipitants depends upon the specific metal content of the colloidal precipitants. In general the presence of chromium (III) depresses the overall PZC while nickel and cadmium, when major waste components, tend to raise the PZC. Aging was found to impact chromium hydroxide dewatering but it is not clear that the theoretical aspects of aging chemistry can be used to predict changes. High molecular weight anionic polymers were effective in conditioning metal sludges with respect to cake formation/filtrate clarity but help dewatering rates very little. Previously developed relationships for inorganic sludges which allowed predictions about sand bed, centrifugation, and vacuum filtration dewatering processes based on gravity thickening data were found to hold for metal sludges. Based on these relationships and the laboratory data gathered here it is concluded that vacuum filtration is the only reasonable process to insure a handleable sludge. If direct reclamation of the metals from the mixed hydroxide slurry is to be attempted centrifugation may be employed. Based on a literature review and a basic economic evaluation, liquid/liquid extraction was recommended for further study as the metal recovery process of choice. (Author).
Author: Malcolm T. Hepworth Publisher: ISBN: Category : Metal coating Languages : en Pages : 198
Book Description
The U.S. Army Toxic and Hazardous Materials Agency has requested that AMAX Extractive Research & Development, Inc. conduct a five-phase program to review literature on the current state-of-the-art in metal recovery from plating wastes, to propose a typical plating sludge composition and aging treatment in lieu of actual U.S. Army plating wastes), to develop a research and design test plan for treating this typical plating sludge, to conduct the test program, and to summarize the results in a final report. The final report proposes a sulfuric acid leach of hydroxide plating sludges, containing copper, cadmium, zinc, nickel, iron, and chromium, to extract greater than 99 percent of the heavy metal values, followed by lime treatment of the resulting filter cake to render it nonhazardous to EP testing. The sulfuric acid leach extract may be treated by selective sulfide precipitation at a controlled pH regime in order to produce a mixed sulfide of copper and cadmium with most of the zinc present in the original extract separate from a leach liquor containing more than 98 percent of the chromium, which does not form a sulfide precipitate, Nickel and iron are not selectively separated under the sulfide precipitation conditions. However, a solvent extraction process using di(2-ethyl-hexyl) phosphoric acid can be used for recovering nickel, iron, and chromium from the resulting filtrate. Originator-supplied keywords: Plating sludge, Acid leach, EP toxicity, Metals, Separation, Extraction, and Recovery.
Author: Clyde S. Brooks Publisher: CRC Press ISBN: 1351091352 Category : Technology & Engineering Languages : en Pages : 193
Book Description
This book is offered as a practical primer on the hydrometallurgy of nonferrous metal reclamation from industrial wastes, as well as a brief discussion of pyrometallurgy, biological, and other separation processes. The objectives are to acquaint nontechnical readers with the subject as well as providing a detailed survey of current research and industrial practice to technical readers concerned with the management of industrial waste.
Author: Vasanthi Sethu Publisher: LAP Lambert Academic Publishing ISBN: 9783838346090 Category : Languages : en Pages : 144
Book Description
This book gives a comprehensive discussion on the removal of heavy metal ions from electroplating wastewater sludge using acid dissolution. Hydrochloric acid, nitric acid and aqua regia solutions were used to dissolve the metals at various reaction conditions. Metals that were tested include Silver, Aluminium, Copper, Tin, Iron, Nickel and Zinc. The optimal recovery values obtained for the above metals were 99.5%, 72.6%, 99.6%, 55.4%, 19.4%, 4.97% and 6.4% respectively. The dissolution process was greatly influenced by the reagent type and reaction temperature. Results obtained were optimised with a statistical software called DOE PRO, where a dissolution model of each metal species was obtained. All models showed good confidentiality and can be used as a tool for future studies for metal extraction from wastewater sludge.
Author: John T. Novak Publisher: ISBN: Category : Heavy metals Languages : en Pages : 281
Book Description
The purpose of this project was to investigate the precipitation of metals from plating facilities, to determine the dewatering characteristics of the resultant metal hydroxide slurries and to evaluate the solvent extraction process for metal recovery and reuse. Individual metals were found to precipitate according to the theoretical solubility calculations, however, mixed metals solutions containing Cr (III) often would form 'co-precipitants.' The co-precipitation would result in certain metals precipitating at pH levels below the range of predicted insolubility. Colloidal metal hydroxides remaining after settling could be removed by filtration using either a gravity filter or diatomaceous precoat pressure filter. Metal removal was effective (>95%) but the filtrate metal concentrations were not sufficiently low to meet effluent requirements. Sludges produced by hydroxide precipitation varied depending upon the pH of precipitation and the specific metals in the sludge. Sludge dewatering characteristics were found to be determined by the mean particle size of the flocs. Polymers improved dewatering rates by increasing the mean floc size. Freshly precipitated chronium hydroxide sludges were found to pass through filtering media because of floc break-up. Polymer conditioning was necessary to prevent sludge penetration through the filter media. Solvent extraction could be used to selectively extract individual metals from a mixed metal sludge but the process was not economical. (Author).
Author: John Holroyd
Author: John Holroyd
Author: Malcolm T. Hepworth
Author: Clyde S. Brooks
Author: E. P. Crumpler
Author: Vasanthi Sethu
Author: Clarence H. Roy
Author: Donald S. Scott
Author: Jerome Kohl
Author: John T. Novak
Author: