RO116489B1 - Process for fractional separation of toxic heavy metals from complex sludge - Google Patents

Abstract

The invention relates to a process of fractional separation of toxic heavy metals from complex sludge having a metal content of Fe, Cr, Cu, Ni, Cd, Zn, Al, Pb resulting during the neutralization of washing water and exhaust solutions in metal coating units. According to the invention, the process of separation of toxic heavy metals from complex sludge ensures the step separation of toxic heavy metals by solubilizing the sludge in autoclave, namely in treating a sludge quantity with an ammonium sulphate solution at a ratio sludge : ammonium sulphate of 1: 1 ....1 :1.5 and S: L of 1 : 6 ....1 : 7 at temperatures ranging from 140 degree to 180 degree C and at pressures of 5 ... 18 at, for 4 ...6 h. The solubilization takes place under continuous oxygen barbotage at a flow rate of 15 l / h, afterwards the iron is separated from chromium and the final suspension is separated into two phases, namely liquid and solid, by filtering or centrifuging. The solid phase is further treated by calcination producing iron pigments at 600 ...800 degree C, while the liquid phase is precipitated in an alkaline medium, chromium being separated therefrom.

Description

The invention relates to a process of fractional separation of metals from complex sludge, containing toxic heavy metals such as Fe, Cr, Cu, Ni, Cd, Zn, al, Pb, Si, resulting in the neutralization of the washing water and of the depleted solutions, from the metal coating lines or from other wastes containing these metals, in order to restore them to the economic circuit in various forms and to pollute the environment.

A process for the recovery of toxic heavy metals from complex sludge is known, which consists in capitalizing on the toxic heavy metals by counter-current solubility of all metals, in the presence of several components, acid-ammoniacal media, with the solution of sulfuric, azotic salts or hydrochlorides thereof from which, by controlled neutralization with NH ₄ H solution and air bubbling, the quantitative separation of Fe and Cr is achieved, which is removed by filtration from the rest of the metals. The rest of the metals that remain in solution as soluble complexes are treated by liquid-liquid extraction, separated and valorized with Cu and Ni, and from the solutions resulting after extraction, Cd and Zn are recovered, by precipitation with sodium sulfide, with cadmium pigments are obtained, and the solid phase, consisting of insoluble metals, is processed either by calcination with pigments, or by inerting by cementation, with various construction materials.

The process of fractional separation of toxic heavy metals from complex sludge, according to the invention, ensures the gradual separation of the heavy, toxic metals existing in the processed sludge, with their complete recovery, in that the solubilization in the autoclave of the toxic heavy metals is done by treating a sludge quantities with a sulphate-ammoniacal solution at the sludge ratio: ammonium sulphate = 1: 1 -1,5 and S: L = 1: 6. 1: 7 at temperatures 140 °, 18 ° C and pressures 5 ... 18 at, for 4 ... 6 h, and the sulphate-ammoniacal solution contains an amount of sulfuric acid in the ratio between stoichiometric and excess 10%, correspondingly at a concentration of ammonium sulphate and sulfuric acid solutions of 15 ... 25%, the solubilization is performed under continuous bubbling of oxygen with a flow rate of 15 l / h, followed by the processing of the suspension resulting from solubilization by filtration followed by the treatment of the solid phase by calcination at temperatures 600 ... 800 ° C, obtaining iron pigments or inerting in Portland cement, mentioned above, and the liquid phase, by precipitation in alkaline environment at pH 5-7, with Cr separation and its recovery as pigment, followed by the aforementioned processing of the solution by extraction L: L, with the recovery Cu and Ni, the regeneration of the organic phase by stripping and the recovery Cd and Zn from the solution left by precipitation with the sulfuric sodium solution Na ₂ S 10%; in one embodiment; Before the solubilization phase in sulphate-ammoniacal medium, the sludge is treated with a solution of sulfuric acid, obtained by diluting the stoichiometric quantity - excess 10% sulfuric acid concentration 15 ... 25% in water, in relation to S-rL = 1: 6-1: 7.

By applying the invention, the following advantages are obtained:

- the possibility of separating and recovering all the metals present in the complex sludge in the form of quality products;

- polluting the environment with a large amount of toxic waste;

- easy to apply with machines known and frequently used in industry;

- the application of autoclaving to the solubilization phase eliminates the successive precipitation operations, implied by the necessity of the separation and quantitative valorization of the iron chromium.

RO 116489 Bl

The following is an example of realizing the process of fractional separation of toxic heavy metals from the complex sludge according to the invention, in relation to the figure which represents the schematic diagram of the steps of the proposed process.

The process of fractional separation of heavy, toxic heavy metals from 50-plex sludge according to the invention consists in the continuous introduction of 0.50 Kg complex sludge or toxic heavy metal waste, in a sulphate-ammoniacal solution in the autoclave. The process is applied to the treatment of sludges from the neutralization of the washing water and the depleted solutions from the metal coating lines, which have particle sizes below 0.5 mm and contain Fe 3-11%, Cr 3-18%, Cu 1 * 4 %, Ni 0.5-2%, 55

Cd 2-5%, Zn 3-8%, Al 1-3%, Pb 0.5-2%, Si 1-5%, Ca 2-4%, Na 2-3%. The sulphato-ammoniacal solution is prepared by dissolving 0.80 Kg of ammonium sulphate in 3 l of water, in the autoclave, followed by the addition of 0.25 l of concentrated sulfuric acid, in a concentration between 15-25%, corresponding to the amount of stoichiometric acid required to bring quantitative in solution of all soluble metals, present in sludge. βο

The sludge-ammonium sulphate ratio is 1: 1-1.5 and the solid-liquid ratio of the ammonium-sulphate sludge mixture is 1: 6-1: 7, at concentrations of 15-25% of the solutions.

Seal the autoclave and raise the temperature of the mixture to

14o ... 15O ° C. 65

The pressure in the autoclave rises to 5 ... 6 at. At this point the oxygen bubbling begins with a flow rate of 15 l / h. The pressure in the autoclave increases further to 11 ... 18 at and the temperature reaches 140 ... 180 ° C, parameters that remain constant throughout the reaction. The total reaction time is 5 ... 6 h. it stops oxygen bubbling, the autoclave is evacuated and the final suspension is separated by filtration 70 or two-phase centrifugation, solid and liquid.

The solid phase contains the highest amount of Fe, namely 98%, together with a small amount of Cr of 2-4% and insoluble metals: Pb Si, Ca; Mg; Al.

The liquid phase contains over 93-98% of Cr; With; Ni; Cd and Zn exist in complex sludge. 75

The solid phase, resulting by filtration, when it also contains Pb, is treated by solubilization in hexafluorosilicylic acid for Pb recovery, as Pb fluorosilicate which is further processed for Pb recovery, as electrolytic Pb next to 1-2% unsolubilized Cr, followed by a phase of washing with water, drying, calcination at temperatures of 6OO ... 8OO ° C, tempering, again filtration washing and drying, after which one obtains Fe pigments for use in the construction materials industry.

In the event that Pb is not recovered, the cake resulting in filtration is inertized by cementation, by mixing them with Portland cement, thus resulting in a product in which the toxic metals are blocked by a process of adding them to the cementation binder, which it is used as a building material. 85

The liquid phase, resulting from the solubilization phase containing all soluble metals having a pH = 1.5, is introduced into a precipitation vessel and treated with a 25% NH4 OH solution until the final pH reaches at 5-7, a value at which Cr precipitates in a large amount and separates from the system by filtration. After this operation Cr is recovered by precipitation, filtration, washing, drying and calcining 90 in Cr pigments. The solution of soluble complex ions resulting by filtration is further processed for the use of Cu, Ni, Cd and Zn. for this purpose, this

RO 116489 Bl solution is treated with an organic phase with alpha hydroxy-oxime, specific for Cu and Ni extraction with maximum yields. From the organic phase, it is separated and recovered with Cu and Ni, after which it is restored to the circuit.

From the solution after liquid-liquid extraction, LL, Cd and Zn are recovered by treatment with a 10% sodium sulphide solution, when both metals precipitate quantitatively, with a mixture of yellow precipitated CdS and ZnS, which, after processing by filtration, washing, drying and calcining, leads to a Cd pigment with Zn ingredient with wide industrial uses. The application of the proposed process leads to solubilization yields of all metals of 90-95% and to a massive separation of Cr and Fe from the solubilization phase.

The process of fractional separation of toxic heavy metals from complex ores, in one embodiment, consists in treating the same amount of sludge as above, with a solution of sulfuric acid, obtained by diluting under continuous stirring in 3 L of water a quantity. of sulfuric acid concentration 15-25%. Carrying out the solubilization in acidic environment leads to the quantitative separation of Fe and Cr in the solid phase which is further processed by subjecting it to the solubilization phase in the aforementioned sulphate-ammoniacal environment, with the recovery of Cr in solution and the separation of Fe in the solid phase. Separation of Fe and Cr in the solid phase leads to easier processing of Cu, Ni, Cd, and Zn solutions.

By performing solubilization in acidic environment at high temperatures and pressures, de

14O ... 18O ° C and 5 ... 18 at, yields of more than 90% solubilization of the heavy, toxic metals present in the complex sludge are achieved.

claims

Claims (2)

1. Process for fractional separation of heavy, toxic metals from complex sludge containing metals such as Fe 3-11%, Cr 3-18%, Cu 1-4%, Ni 0.5-2%, Cd 2 -5%, Zn 3-8%, Al 1-3%, Pb 0.5-2%, Si 1-5%, Ca 2-4%, Na 2-3%, consisting of autoclaving at temperatures and pressures elevated, followed by filtration washing, drying, solid phase calcination, obtaining Fe pigments, or inertization by cementation and liquid phase processing, precipitation with NH ₄ H or NaOH, filtration, washing, drying, precipitate calcination, obtaining Cr pigments, and the processing of solutions of ammoniacal complexes by L: L extraction, with Cu and Ni recovery, followed by regeneration of the organic phase by stripping with depleted Cu and Ni extractants, Cd and Zn precipitation from solutions from Cu and Ni recovery, and the processing of the precipitate in Cd and Zn pigments, characterized in that the solubilization in the autoclave of the heavy, toxic metals is done by tr the amount of sludge with a sulphate-ammoniacal solution at the sludge ratio: ammonium sulphate = 1: 1 - 1.5 and S: L = 1: 6. 1: 7 at temperatures 140 ° C, 18O ° C and pressures 5-18 at, for 4 ... 6 h, the sulfato-ammoniacal solution containing an amount of sulfuric acid in the ratio between stoichiometric and excess 10%, corresponding to a concentration of solutions of ammonium sulphate and sulfuric acid of 15 25%, solubilization being carried out under continuous bubbling of oxygen with a flow rate of -15 l / h, followed by processing of the suspension resulting from solubilization by filtration, followed by treatment of the solid phase by calcination at temperatures 6OD ... 8OD ° C, with the above mentioned iron pigments or inertization in Portland cement, and of the liquid phase by precipitation in alkaline environment at pH 5-7 with Cr separation and its recovery RO 116489 Bl / as pigment, followed by the above-mentioned processing of the L: L extraction solution, with Cu and Ni recovery, regeneration of the organic phase by stripping and Cd and Zn recovery from the remaining solution, precipitation with sodium sulfuric Na ₂ S solution 10%. 2. Process for the fractional separation of heavy metals, toxic, from complex sludge, characterized in that, in one embodiment, Before the solubilization phase in sulphate-ammoniacal environment, the sludge is treated with a solution of sulfuric acid, obtained by dilution of stoichiometric quantity - excess 10% sulfuric acid concentration 15-25% in water, ratio S = L = 1: 6-1: 7.