Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/04—Working-up slag
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• Slag is non-volatilized solid residue extracted from combustion stoves on industrial sites. Generally evacuated by a hydraulic flush to a receiving pit and then containing 3 to 30% of water, they have the appearance of black solid more or less divided and very heterogeneous.
• slag must therefore be understood in the widest possible sense. It will relate to all combustion products and residues, for example clinkers likely to contain heavy metals more or less eligible for runoff or meteoric water. They may also consist of fly ash originating, for example, from the incineration of urban residue.
• Slag is often characterized by a silico-aluminous gangue containing metallic oxides, essentially metallic oxides and lower contents, oxides of chromium, copper, nickel, zinc, even cobalt and lead (table 1 ) Their compositions can naturally vary considerably from one site to another.
• Table 1 Multi-element analysis of the slag from Tredi France (ST 1), Tredi Salaise II (S II) and Tredi Saint-Vulbas (SV 1).
• the metals present in the slag can be water-soluble, exchangeable, associated with amorphous or crystallized oxides and hydroxides, or in the form of precipitates, such as carbonates or sulphides.
• amorphous or crystallized oxides and hydroxides or in the form of precipitates, such as carbonates or sulphides.
• precipitates such as carbonates or sulphides.
• the first leachate is obtained by filtration of the supernatant after centrifugation of the mixture (2000 for 15 minutes). The color, eye, conductivity and pH are then measured. The solid is then taken up for 2 new extractions with consequently the obtaining of two leachates (or additional eluates. At the end of these operations, the chemical oxygen demand (COD), the total organic carbon (TOC) and an analysis mineral are carried out on the eluates.
• COD chemical oxygen demand
• TOC total organic carbon
• an analysis mineral are carried out on the eluates.
• Table 2 Valuation of bottom ash from household waste incineration in public works concentration-thresholds given by the leachable fraction obtained by the standardized AFNOR test (x 31-210).
• the bottom ash is considered to have a low leachable fraction. The corresponding production can then be used in public works.
• Reading tables 4, 5 and 6 is facilitated as soon as the following remarks are taken into account, concerning the four right columns of the middle and lower sub-tables:
• the "total quantity extracted from the raw waste” e "mg per kg” corresponds for each element to 10 times the sum of the quantities extracted by the three extraction solutions (or extractants) used to treat 100 g of the same waste.
• these numbers are to be compared with the standards which appear in the three right-hand columns of the median sub-tables (and which correspond to the values indicated in the columns "French standards class I” "French standards class II” in table 3 and "Valuation standard in Works public "in Table 2).
• the soluble fraction of ST 1 slag (table 4 risks inducing pollution constituted by copper (total quantity extracted in mg / kg higher than class II norm and not in conformity with a recovery e public works), zinc, nickel and chloride (increasing solubilizations in successive eluates).
• the object of the invention is precisely to fine-tune a process allowing the preservation of the environment while limiting the expensive storage of slag, especially in a class I landfill. It has particularly pleased a process for the stabilization of residues combustion, whatever its origin by extraction of the soluble metallic fraction
• the invention more particularly aims, e reference to French and European standards e force, to obtain in a particularly simple way the detoxification or "inertization" of the slag with the poin which they can then be stored in class II landfills as non-hazardous waste or even recycled.
• this consists in first carrying out o several leaching of the slag, if necessary previously ground to sufficiently small particle sizes, in particular at values less than 50 mm to allow sufficient contact between combustion residues and an aqueous solution or leach liquor, having a sufficient concentration of cations (K + , Na + , Ca 2+ ) or exchangeable protons in the form of chlorides with the heavy metal cations present in these residues.
• This leaching must be sufficient to ensure the transformation of at least part of the determined metals, in particular heavy metals contained in these slags, into soluble chlorides extractable by this leaching liquor, and their effective extraction in sufficient proportions so that: on the one hand, a standardized elutio test subsequently applied to the slag thus treated attests to the decrease in the successively solubilized quantities of each of these metals determined during repeated extraction tests carried out with a standardized leaching or elution solution in accordance with this test and, on the other hand, the sum of the quantities solubilized in the eluates resulting from the extractions with the aforesaid standardized solution, is situated at values corresponding to concentrations lower than the threshold concentrations also predetermined by the above standardized test for each of these metals.
• the number of successive elution tests and the concentration thresholds are determined by existing or future standardized protocols.
• the standardized study protocol used in this study corresponds to the AFNOR standard (X31210, 1988), the detailed implementation of which has been recalled above.
• the repeated elution tests with the standardized solution are then 3 and the standardized solutio is itself constituted by a demineralized ea saturated with air and CO 2 at pH 4.5 and with a resistivity of between 0.2 and 0.4 M ⁇ .cm.
• the elution tests with the standardized solution are then carried out by mixing with the treated slag (for example used in an amount of 100 g) for 1 hour and with stirring.
• the cations or protons exchangeable in the form of chlorides from the liquor used for the initial leaching of the slag can be provided in any form allowing the goal to be achieved.
• the leach solution may consist of acid dilute hydrochloric acid, more particularly for the treatment of slag of a basic character, for example slag which, when it is suspended in water for a sufficient time, has the effect of bringing the pH to values of order of 9 to 10
• solutions of chlorides of alkali or alkaline earth metals rather than hydrochloric acid.
• the hydrochloric acid concentrations of the acid solutions applicable to treatment in accordance with the invention will have molar concentrations most often comprised in intervals of 0.01 M to 1 M, while the metal chloride concentrations alkaline or alkaline earth solutions leaching corresponding will most often be included in the interval 0.01 M, especially 0.05 M, at 5 M.
• a hydrochloric acid solutio 0.1 N is an RESPONSIVEN particularly suitable for the treatment of basic slag, while a solution of 'potassiu 1 M or 0.01 to 2 M calcium chloride, in particular 0.09 M and 0.15 M, will allow the extraction of the mobilizable metals contained in the slag having a low acidity.
• This static or dynamic leaching slag / extractant ratio 1.1
• slag / extractant ratio 1.1 will be followed by a draining of the leachate to a storage tank. They may also be treated themselves as discussed below.
• the Sain Vulbas slag (SV 1) was previously dried before being brought together as an average sample.
• the slag from Salais (SU) was treated as it was.
• the France (ST 1), Salaise II (SU) and Saint-Vulba (SV 1) samples have a pH of 10.0, 7.6 and d 8.2, respectively.
• the extraction tests are carried out by leaching tests in a clogged column or in dynamic leaching (with stirring) on 100 g of slag.
• the reagents used (100 ml per 100 g of slag) are 0.1 N hydrochloric acid, potassium chloride 1 or calcium chloride 0.09 M and 0.15 M. They are left in contact from 2 to 24 hours with slag e can undergo 2 recycling (ie at least 3 times 2 hours of slag / extraction liquid contact).
• the pH, conductivity and chemical composition are determined on the leachate obtained.
• the slag sample is then rinsed with at most 2 times 100 m of distilled water and then the standardized leaching test is applied. Results:
• the extractants used in the mobility tests form with the slag elements soluble metallic chloride, the speed of formation of which is a function of their solubility constant.
• potassium chloride 1 results in a significant solubilization of calcium and copper in the slag ST 1.
• Potassium (excess reagent) and sodium which were not assayed in these tests, proved to be found during the assays , be matrix elements having a negative impact on the analyzes (yellow emissio in the plasma).
• the solubilized trace elements are indicated in table 7.
• the most mobilizable elements are manganese and magnesium for the major elements, the trace elements being solubilized according to variable proportions (table 7).
• the analytical perturbation, due to a massive solubilization of alkaline earth elements is also noticed in these solutions coming from SU slag.
• Hydrochloric acid more effectively mobilizes metals, in particular copper in ST 1 slag.
• the dissolution of the alkaline earths by this reaction leads to a disturbance in the dosage of calcium, whereas the yellow emission of the plasma is synonymous with a strong presence of sodium (Table 7).
• Table 7 Determination of the mobility of 9 major elements and of 7 trace metals during leaching in a fouled column of 100 g of slag per 100 ml of extractant (3 successive passages). Analyzes of leachate obtained by assaying metallic elements in solution with a plasma emission spectrophotometer. Results expressed as a percentage by weight of the initial contents.
• Table 8 Determination of the mobility of 9 major elements and 7 trace metals during rinsing (2 times 100 ml of distilled water) of the columns engorged with 100g of slag after treatment with 100 ml of extractant. Analysis of water obtained by dosing metallic elements in solution with a plasma emission spectrophotometer. Results expressed as a percentage by weight of the initial contents.
• the purpose of the rinsing waters is to eliminate the excess of reagent before the implementation of the standardized leaching test. During this operation, a low mobility of the elements should be noted whatever the extractant and the slag considered (table 8).
• the leaching tests must obey French class II standards and European standards on non-hazardous waste or standards for the recovery of bottom ash in public works.
• Tables 11 and 12 illustrate the results obtained under similar conditions, in standardized leaching tests after treatment of the slag, S after treatment with potassium chloride (table 11) and hydrochloric acid (table 12).
• Salaise II slag (S II) without prior treatment generates eluates whose toxicity thresholds are lower than French class II standards but higher than European standards for non-hazardous waste and recovery standards in public works. After treatment with potassium chloride, the eluates produced comply with European standards and the standards for recycling bottom ash.
• Table 13 Summary of the results obtained during the treatment of slag. Comparison of the results of their leaching to European and French standards on the landfill of waste. Threshold concentrations given for the leachable fraction obtained by the German ballast for European standards (100g of dry waste / I l of water) and by the standardized Afnor test for French standards (100g of raw waste / l of water) . The results are expressed in solubilizable quantities in mg / kg.
• the leachate resulting from the application of the leaching procedure contains metal chloride salts as well as an excess of extractant.
• the average composition of leachate and rinsing water for all treatments, obtained during no experiments on 100 g of slag, is given in table 14.
• Table 14 Chemical analysis of leachate and rinsing water. Average composition obtained from the different treatments performed on the slag from France (ST 1) and Salaise II (S ⁇ ).
• Leaching has been extended to other reagents under different conditions.
• the leaching was carried out under agitatio (dynamic leaching) in 2-liter bottles with at most 1 liter of extractant in the presence of 100 g of slag. In view of the preliminary experiments, the incubation was maintained for 2 hours at room temperature. A single rinse with at most u liter of distilled water is carried out after treatment. The solid / liquid separation is carried out by centrifugation at 2000 g. For analytical purposes, filtration is carried out on Millipore membranes with a diameter of 0.45 m.
• SU slag was also extracted using a reconstituted calcium effluent (calcium chloride 10g / l, which corresponds to a molar concentration of 0.09M). They were also leached with 1M potassium chloride.
• Salaise II slag from saline or reconstituted discharges see their soluble fraction decrease to become consistent with a recovery in public works
• the COD of leachate is lowered, as well as the solubilization of chlorides, while the sulphate content reaches a lower concentration at the threshold values of the public works standard (as modified in 1992).
• the decreasing solubilization of nickel is also established (Tables 20 and 21).
• control slag contains 1.83 carbon in the form of carbonates while the treated slag has a concentration of 2.38%, that is to say a 30% increase in the carbonate content.
• Resistivity (Ohm.cm) 94 925 D.C.O mg O2 / I 414 0 C.O.T me / 1 6 7
• Chlorides limit detection and (raw values)
• biosorption is the sequestration of metal ions by solid material of natural origin.
• This general term brings together very diverse mechanisms: ingestion of particles active transport of ions, complexation, adsorption and inorganic precipitation on the biosorbent.
• a biosorbent whose use seems particularly advantageous is chitosan.
• Chitosan is the main derivative of chitin (poly N-acetyl D-glucosamine). It is a saccharide polymer consisting of a long linear polymer chain with glucosamine units, linked by (1-4) glucosidic bridges.
• chitosan is obtained by deacetylation of chitin, itself extracted from the exoskeleton of crustaceans, myriapods and other arthropods or even microorganisms, fungi.
• the deacetylation rate ranging from 80 to 100% and the average molecular mass from 5,000 to 1,000,000 have the consequence of fixing the turbidity, viscosity and solubility of the solutions.
• This solubility of chitosan, with a low degree of N-acetylation, is only obtained in an acid medium diluted in the pH range ⁇ 6 It is linked to the presence of amino functions on the C- glucoside units, conferring on this polymer u weak polybase behavior.
• chitosan in water treatment is indeed a way of the future.
• PRO FLOC Protan
• Its characteristics are the following flakes / powder; free amino form (-NH 2 ), medium purity.
• chitosan chitosan beads, Fujib Inc, Shizuo a
• SIGM chitosan SIGM chitosan
• biosorbents can be used in place of chitosan. We could for example use some of the biosorbent identified below. Their biosorption characteristics do not always coincide with those of chitosan. The choice of the most suitable biosorbent will often result from the contents of the leachate obtained by applying the first part of the process according to the invention to the slag which was to be treated.
• Incubation is carried out at 25 ° C with gentle shaking; The samples are taken after 3, 6, 12 24, 48 and 72 hours of contact.
• Figures 4 to 9 provide relative curves, the kinetics of adsorption of lead, copper, chromium, cobalt, zinc and cadmium respectively on different biosorbents.
• Chitosan does not seem to immobilize lead in the conditions of the experiment ( Figure 4).
• copper has a very similar behavior towards chitin, fungal and bacterial biomass and feather meal; its immobilization is close to 10 and remains practically constant.
• Chitosan is the best copper adsorbent and takes on a colored hue in its presence, 50% of copper sulphate is chelated in 72 hours (Figure 5).
• chromium alone has an affinity for chitosan and its adsorption reaches 6% in 72 hours of incubation (Figure 6).
• cobalt has an alternate adsorption and desorption profile for all of the biosorbents tested. The percentage fixed varies between 2 and 8% (figur
• biosorbents used may be weakly active in certain conditions, but become so in others. This is the case, for example, for chitosan with regard to lead and copper.
• biosorbents are of particular interest, especially when they can be regenerated.
• chitosan is particularly effective. The tests briefly reported below demonstrate the capacity of chitosan to be regenerated by treatment with an exchange reagent or an acid.
• Another parameter can in particular reside in the presence of larger quantities of biosorbents with respect to the element to be extracted. This is also the case for lead and zinc. Under the conditions of the experiment carried out as indicated below, the quantity of lead absorbed can increase considerably when the relative proportion of the biosorbent increases with respect to the concentration of metal to be adsorbed.
• Copper is the element with the best affinity for chitosan; with a salt / biosorbent ratio of 0.8 the metal chelation is practically complete in 24 hours of contact, the value of the initial pH does not seem to influence the fixing capacity of the biosorbent, however its basic power tends to orient the pH of the medium towards values close to 7 where the competition for protons becomes less.
• Zinc another element tested, has a lower affinity compared to copper and its percentage of fixati reaches 60% in 24 hours for a salt / biosorban ratio of 0.8.
• the pH of the medium changes in an identical manner to the experiments with copper.
• cadmium has a behavior similar to zinc, its degree of fixation reaches 60% in 24 hours for an identical salt / biosorban ratio.
• Lead is adsorbed at 91% for a salt / biosorbent ratio of 0.8. This metal is weakly exchangeable, it is partly mobilized by adding hydrochloric acid.
• Nickel has a lower affinity for chitosan, its percentage of fixation reaches 60% in 2 hours for a salt / biosorbent ratio of 0.8. Desorption is effective (78%) following displacement of the reaction equilibrium by addition of hydrochloric acid.
• FIG. 10 is a block diagram of an industrial device which can be envisaged for this purpose.
• the leachate will be directed to a reactor containing the chitosan or to a mixed device comprising da a separate reactor or a mixture of another biosorban (eg stabilized biomass).
• This will be provided with a recycling loop in order to obtain a complete water treatment.
• This metal-free water can be discharged into the river or possibly recycled as slag rinse water.
• the chitosan will be regenerated by desorption of the metals using an acid eluent, an operation possibly followed by reconditi ⁇ nêt of the biosorbent by adding sodium hydroxide. Regeneration will be carried out alternately on one of the treatment chains (route I or II).
• the acid eluate will be sent to a storage tank before final solidification, but the recovery of metals and the recycling of water may be envisaged later.
• the biosorption tests are carried out with stirring for 2 hours at 25 ° C. and without pH control 100 ml of an effluent of composition similar to the slag leachate are placed in the presence of 50, 100 or 250 mg of fungal biomass (Rhizopus arrhizus ) cultivated in the laboratory.
• the determination of the mineral elements is then carried out on the solutions obtained after filtration on millipore membranes with a diameter of 3 m then 0.45 m.
• Rhizopus arrhizu ⁇ are particularly effective in removing heavy metals in trace amounts from a calcium matrix.
• the effluents or leachate can be treated continuously in a device comprising a stirred bath fed with the effluents to be treated and the biomass and a decanter for the solid / liquid separation.
• the liquid supernatants are eliminated and the solid materials (biomass) are either recycled into the food as soon as they are not yet saturated with metals, or to a purge when they are saturated. They are then concentrated (ultimate waste) and, possibly destroyed, for example by incineration, or solidified, for example by vitrification for storage.
• FIG. 11 provides an illustration of results obtained in tests involving three different concentrations of "Rhizopus arrhizus (study of the adsorption of different metals contained in effluents. Calculation of the percentage of elimination and confidence interval at 5% after a hour contact with stirring in the presence of Rhizopus arrhizus).
• Table 24 Biosorption of heavy metals. Study of the composition of effluents before and after treatment on fungal biomass. 3 repetitions per test. Concentration in ⁇ g / 1 and confidence interval at 5%.

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• 1992
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