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Technicalfieldoftheinvention

The present invention relates to a hydrometallurgical process whose main purpose is recovery ofthe metalsV,Mo,Niand Co from many typesofindustrialwaste.

Among thewastesthatcan betreated formetalrecovery arethe variouswastesfrom the oilindustry such asLC-Fining catalysts(LCF, Lummus-Citiesexpanded-bed process)or sludgesfrom the oilrefining process;in addition to this,waste from the pharmaceuticalindustry such asMo-based catalystscan alsobetreated.

In general,allwasteshavingcharacteristicssimilartothewastes specified abovein termsofthechemicalspeciespresentcan betreated.

The proposed process is economical, easily manageable and innovativesincetheprocesseshithertoreportedin theliteratureconsist ofeither thermalprocesses or a combination ofthermaland aqueous processes,oreven hydrometallurgicalprocesses,butwith theuseofacid leaching solutions.Also,one ofthe process solutions proposed in the present invention takes place under atmospheric pressure and at a temperatureofnomorethan 60°C,which isveryadvantageousin terms ofoperation andin particularin termsofenergy used.

Finally,the proposed process is very flexible and can easily be adapted to differenttypes ofwaste withoutmajor modificationsto the processschemeandplantlayout.

Priorart

Catalystsareusedin awiderangeofindustrialapplicationssuch as oil refining, petrochemical production, polymer processing, environmental protection reactions and chemical synthesis. In the petrochemical sector,catalysts are indispensable in the conventional production ofgasoline,diesel,heavy hydrocarbons,plastics,etc.

Over time these catalysts undergo an inevitable process of gradualdeactivation duetothe deposition oforganicmaterialormetal poisoning. Generallyregeneration andreusecan onlybeappliedforacertain number of cycles,and in some cases,since the technology for their regeneration andreactivation isnotavailabletorefiners,spentcatalysts aredirectly discarded assolid waste.

Chemicalprocesses based on high temperature operations are currently the mostwidely used technologiesforthe treatmentofthese wastes.Pyrometallurgicalprocessesin particularrequiretemperatures ofup to 1600°C,with associated costandpollution problems.

PatentKR 10-1189183 describes a pyrometallurgicalprocess in which V,Ni and Mo can be recovered from spent HPR catalysts as ferroalloys.The reductive melting process through a carbo-thermal reaction in an electricarcfurnaceisfirstcarried outatatemperatureof 1600°C.TheFe-V-Ni-Moalloy obtained isthen treated atabout1200°C in thepresenceofoxygen and iron oxidefortheselectiveoxidation ofV. The resultingsludgeisthen subjected toan alumino-thermalreduction processtoproduceFe-V alloy.

Other processes developed involve a combination of heat treatment and hydrometallurgical processes. Compared to pyrometallurgical processes, hydrometallurgical processes have the advantagethatthey can be controlled and managed much more easily; moreover, most of them have no emissions of substances that are hazardousto humans and the environmentand generally require less investment.

US8287618B2 describes a processforthe recovery ofNi,Mo,V, Co and Al using a combination of heat treatment and a hydrometallurgical process.The process starts with de-oiling of the catalyst in toluene or naphtha solution.It is then ground and the resultingpowderissubjected tothe removalofcoke and sulfurspecies by means of a thermal process carried out at around 500°C. Subsequently,theprocessiscontinuedwith totalleachingofthesolidin EDTA solution using an ultrasound bath.In thisprocessNi,V,Co and Mo are almost completely dissolved and the solid residue is a pure aluminaproduct.Theresultingsolution issubjectedtotheprecipitation ofEDTA usingnitricacid.OncetheEDTA hasbeen recovered from the solution,a solventextraction processisperformed torecoverV,Mo,Ni and Cu atdifferentpH.

CN105274344A discloses a process in which the catalyst undergoestworoasting stages.Thefirstisperformed toremovecarbon and oilata temperature of500-600°C.The second isperformed in the presenceofsodium carbonateat600-850°C.Thetreatedcatalystisthen ground and leached with water athigh temperature to recover soluble molybdenum andvanadium salts.

US 2007/025899 discloses a hydrometallurgicalprocess for the recoveryofV,MoandNi.Theprocessinvolveswashingthecatalystwith an organicsolventsuch asToluene,XyleneorKerosene (othersolvents may alsobeused)underpressure orathigh temperatures.Leaching of thewashed catalysttakesplacewith NH ₃ and O ₂ athigh temperatures. In this way V is directly precipitated as NH ₄ VO ₃ .Niis recovered by solventextractionwhileMoisrecoveredlastas(NH ₄ ) ₂ MoO ₄ bychanging thepH.

Table 1 below summarises the main processes developed in the artfortheindustrialprocessingofV-andMo-based catalysts.

Table1 Table 1(continued) Table 1('continued) Table 1(continued)

Summary oftheinvention

Thepresentinvention relatestoahydrometallurgicalprocessthat enablesV,Mo,Niand Cotoberecovered from many typesofindustrial waste.Among the wastes that can be treated are the various wastes from the petroleum industry such as LC-Fining type catalysts (LCF, Lummus-Cities expanded-bed process) or sludge from the petroleum refining process;in addition,waste from the pharmaceuticalindustry such asMo-based catalystscan alsobetreated.

In general,allwasteshavingcharacteristicssimilartothewastes specified abovein termsofthechemicalspeciespresentcan betreated.

Other objects will also be evident from the following detailed description oftheinvention.

Thehydrometallurgicalprocessdescribedinthisdocumentisvery simpleand achieveshigh recovery yieldsforthemetalsofinterest.

Two similarprocess solutions are presented:with alternativeA stepsand alternativeB steps.

The treatmentprocess according to the invention comprisesthe followingmain steps:

I) WashingoftheLCF catalystwith apolarsolventsuch asacetone or ethanolor a surfactant,either as an alternative to the solvent or subsequently to it, filtration, washing with water, filtration and subsequentrecovery ofthesolventused;

II-A) Drying of the solid obtained in step I) and grinding with a planetary ballmill,where grinding may also carried outbefore step I), ifnecessary;

III-A)Basicleachingofthesolid (obtainedfrom step II-A))todissolveV and/orMousingan aqueoussolution ofsodium hydroxideandhydrogen peroxide (H ₂ O-NaOH-H ₂ O ₂ ) for the catalyst and the sludge;or with ozone (O ₃ )as an oxidant instead ofor in combination with hydrogen peroxide;fortheMo-based catalyst,aftergrinding,an aqueoussolution ofsodium hydroxide withouthydrogen peroxide (H ₂ O-NaOH)is used; finally,theresidualsolidisfiltered andwashedwith water;

IV) Mixing ofthe solution and thewash waterfrom alternative step III-A) or III-B ) described below, purification from arsenic and phosphorus and neutralisation with an inorganicacid (sulfuricacid or hydrochloric acid) for selective precipitation of vanadium (V) with ammonium chloride or ammonium sulfate (NH ₄ CI or (NH ₄ ) ₂ SO ₄ ); separation ofthe solid precipitate from the solution by filtration and washingwith an ammonium chlorideorammonium sulfatesolution;

V) Mixing of the solution and wash water from step IV), neutralisation with HCl or H ₂ SO ₄ and selective precipitation of molybdenum (Mo)with theaddition ofacationicpolyelectrolytesolution forsolutionsfrom LCF catalysttreatmentand sludge;forthe solution from Mo catalysttreatment (step III-A)),afterthe acid neutralisation step,ammonium chloride orammonium sulfateisadded toprecipitate Mo asammonium molybdate((NH ₄ ) ₂ MoO ₄ );theprecipitateobtainedis recoveredfrom thesolution byfiltration;

VI) The residualsolid from theleachingprocessin step III-A)orIII- B)(alternativedescribedbelow)fortheLCF catalystisleachedwith an acid solution ofsulfuricacid andhydrogen peroxide (H ₂ SO ₄ -H ₂ O ₂ -H ₂ O); at the end of the reaction the residual solid is separated from the solution by filtration andthen washedwith water;

VII) Theleachingsolutionfrom stepVI)issenttothenickel(Ni)and/or cobalt(Co)recovery step;Nirecovery can becarried outby electrolysis orprecipitation while Co recovery can be carried outby precipitation. Precipitation forboth elements is carried outby neutralisation ofthe solution with sodium hydroxide and subsequent addition of sodium carbonate(Na ₂ CO ₃ )oroxalicacid(C ₂ H ₂ O ₄ );inthecaseofjointtreatment of Ni-Mo and Co-Mo catalysts,solvent extraction may be used,for example using di-(2-ethylhexyl)phosphoricacid (D2EHPA)or CIANEX in an organicdiluentsuch asn-heptane;

VIII) The solution from step V)for the treatment ofLCF or refining sludgeistreated with an organicsolventtoremove residualMo andV ions.

As an alternative to steps II-A)and III-A)described above,itis possibletocarry out:

II-B) Roastingofthe solid obtained in step I)inside a rotary kiln with subsequentgrindingwith aplanetaryballmill,wheregrindingmayalso carriedoutbeforestep I));

III-B)Leaching ofthe solid (obtained from step II-B)) to dissolve V and/orMo with an aqueous alkaline sodium hydroxide solution (H ₂ O- NaOH) or ozone (O ₃ )as described for step III-A)to oxidise the metals remainingassulfidesduringstep II-B).

BriefDescription oftheFigures

Figure 1showsablock diagram ofthehydrometallurgicalprocess relatingtothepresentinvention.Thediagram refersin particulartothe treatmentofLCF catalyst,butcan easilybeadaptedtoalltypesofwaste by followingwhatwassaid earlierin thisdocument.In thecasewhere LCF istreated using alternativeA,afterthewashingin step I)thereis air drying,grinding which may also be carried outprior to step I and basic leaching with hydrogen peroxide and sodium hydroxide III- A), whereozone(O ₃ )may alsobeusedasdescribedabove.In thecasewhere LCF is treated using alternative B,calcination is carried out in the rotary kiln (step II-B))afterthewashingin step I),a calcination which may also be carried outbefore step I,and leaching iscarried outwith sodium hydroxide (step III-B)). In the case of Mo-based catalyst, grindingandleachingiscarried outasdescribed in step III-A)).

Figure2showstheeffectofremovingtheorganiccomponent(step I))on theestimatedheatprofileinsidetherotary kiln in step II-B).

Detailed description oftheinvention

In the case ofthe treatmentofspentLCF catalysts,the process proposedin thisdocumentisasfollows.

The LCF catalystiswashedwith apolarsolventsuch asacetone or ethanol,or a surfactant,either as an alternative to the solvent or consecutively,for 15-45 minutesata solid concentration of10-30% w/v. In thisway alargepercentageoftheorganicsubstancesinitiallypresent on thespentcatalystcan beremoved.Next,filtration iscarried outand thesolidiswashedwith water,followedbyfurtherfiltration toseparate thesolidphasefrom thewash water(step I)).

The spentsolventisrecoveredin aflash stageandseparatedfrom theoilycomponent.Thesolvent,recoveredwith ayieldofmorethan 90% anda purityofabout99%,isrecirculatedinthesystem withtheaddition ofa smallamount ofmake-up (amount ofacetone to be added to the system toreturn tothesameconditionsasthefirstwash). Theuseofaveryvolatilesolventsuch asacetoneorethanolallows thesolventtobealmostcompletelyrecoveredwith relativelylow energy consumption, unlike the various solvents used in other similar processes.

The washed catalyst undergoes drying at a temperature of25- 60°C,followedby grindingwith aplanetary ballmillto a solid particle size oflessthan 200 pm (step II-A)).Grinding can also be carried out beforethewashingstep (step I).

The groundsolidissubjectedtobasicleachingin accordancewith step III-A)to dissolve V and/orMo using a solution containing water, sodium hydroxide and hydrogen peroxide (H ₂ O-NaOH-H ₂ O ₂ ),in the followingconcentrations:

- 0.5-4M,preferably 1-2.5M,sodium hydroxide;

- 0.5-2M,preferably 1-2.5M,hydrogen peroxide.

Leaching is performed at a solid concentration of 10-20% for a timeof1-4 hoursatroom temperature,with orwithoutstirring.Ozone (O ₃ ) may be used as an oxidant instead of or in combination with hydrogen peroxide.By continuously feeding gaseous ozone into the reaction environment,itispossible to solubilise the gas in the liquid phase.In this way,oxidation of the various metals present can be achieved by reducingtheamountofhydrogen peroxiderequired forthe reaction, and the hydrogen peroxide can be completely replaced by ozone.Attheendofthereactiontheresidualsolidisfilteredandwash ed with water.

When treating residual sludge from the petroleum refining process,step III-A)iscarried outdirectly by leachingwith the aqueous solution ofsodium hydroxide and hydrogen peroxidementioned forthe treatmentofLCF.

When treatingMo-based catalyst,grindingwith aplanetary ball millisused to achieve an average solid particle diameter ofabout80- 120 m.Theground solid istreated asmentionedforstep III-A)with an aqueoussolution of1-3M sodium hydroxide,ata solid concentration of 10-20% foratimeof1-3hoursatatemperatureof25°C (±5°C),with or withoutagitation,preferablywith stirring.Attheendofthereactionthe residualsolidisfiltered andwashedwith water. Step IV)ofthepresentinvention relatestotheselectiverecovery ofvanadium by meansofaprecipitation step.Theleachingsolution and the wash water from Step III-A) are mixed and,once purified from elements such as arsenic and phosphorus, are neutralised with an inorganicacid (i.e.sulfuricacid orhydrochloricacid)untilthepH value is in the range 6-8.Then,in accordance with step IV, ammonium chlorideorammonium sulfateisadded in therange2-3in excessofthe stoichiometric amountrequired for reaction with the vanadium in the solution.Selective precipitation ofV iscarried outata temperature of almost40°C (±5°C)for 1-2 hours.Finally,the precipitate is separated from the solution by filtration and then washed with an ammonium chloride orammonium sulfate solution ata concentration of1-5 % w/v. In step IV, ammonium ions react with vanadium to give rise to ammonium vanadate, also known as ammonium metavanadate (NH ₄ VO ₃ ).

The metavanadate iswashed to replace the solution in the cake and recoverthesolublemolybdenum presentin it.

Ammonium metavanadate can be heated above 450°C in an oxidisingatmosphere.ThisdecomposesintogranularV ₂ O ₅ and gaseous ammonia.GranularV ₂ O ₅ can bemelted and reduced toflakes.

Fortheprecipitation ofMo,thesolution resultingfrom step IV)is subjected to neutralisation with HClorH ₂ SO ₄ to pH 1-1.5 during step V).A cationicpolyelectrolyte(PA)solution isadded ataconcentration of 5-15% w/v forthe solutions derived from the LCF catalystand sludge treatment.Precipitation isperformed atatemperatureof25°C (±5°C).

From step III-A) for the treatment of Mo-based catalyst,the leaching solution is neutralised to pH 1.5-3 with HCI.To achieve the precipitation ofmolybdenum as ammonium molybdate ((NH ₄ ) ₂ MoO ₄ ), ammonium chlorideisaddedtoaconcentration of10-30g/l.Thereaction isperformed atroom temperature.Theprecipitateobtainedisrecovered from thesolutionsby filtration.

In stepVI)theresidualsolidfrom theleachingprocessin step III- A)forLCF catalystisleachedwith sulfuricacid and hydrogen peroxide in thefollowingconcentrations: - 1-2M sulfuricacid;

- 1-2M hydrogen peroxide.

Leaching takes place over a period of 2-4 hours, at a solid concentration of5-15%.Theprocessiscarried outatroom temperature. At the end ofthe reaction,the residual solid is separated from the solution by filtration andthen washedwith water.

The solution from step VI)issentto step VII)fortherecovery of Ni and/orCo.Nican berecovered by electrolysisorprecipitation while Co can berecoveredbyprecipitation.Both elementsareprecipitatedout by neutralising the solution with sodium hydroxide and then adding sodium carbonate (Na ₂ CO ₃ )oroxalicacid (C ₂ H ₂ O ₄ ).

The aqueoussolution from themolybdicacidprecipitation section described in step V) is suitably neutralised to a pH of 2.0-2.5 and subjected to an oxidation processwith hydrogen peroxide to bring the vanadium toitshigheroxidised form.The solution isthen treated with an organic solution containing a quaternary amine asin step VIII)to extracttheresidualmolybdenum and vanadium and obtain a raffinate free ofthese elements.The extraction processisvery fast,and the Mo and V ions,present as anions,are captured by the extractant in the organicphaseunderacid conditions.Theextraction yieldisnot100% in a single stage,so severalstages are required to recover allthe ionsof interest.Thisoperation isperformed in mixersand settlersin seriesor in countercurrentliquid-liquid extraction columns.

The organic solution (extract) is brought into contact with an alkaline stripping solution that counter-extracts Mo and V (again as anions) in several stages.This basic solution is recycled before the arsenicand phosphorusprecipitation step in step IV).The regenerated organic solution is stored and then reused for a further solvent extraction process,with theaddition ofa smallamountofmake-up.

The processprovidesthatalternative B uses a different system for oxidising the differentchemicalcompounds.ProcessB can be used instead oftheprocessdescribed in alternativeA orin combination with it via software management. The possibility of using the two alternatives in combination gives the process considerable flexibility according to different market conditions.This flexibility has notbeen found in otherprocessesproposedin theliterature.

In the case of alternative B,the oxidant is oxygen,which is reacted with the material inside a rotary kiln at a temperature of approximately 800-900°C.Reducing the amountoforganic substances presenton thecatalystisessentialtoavoidan uncontrolledtemperature rise in the furnace resulting in sintering ofthe alumina.Thisleadsto difficultiesin the oxygenation and complexation ofthe materialwith a consequentdecreasein theextraction yield ofmetalsofinterestduring leaching.In some processes described in the literature,the organic materialis reduced through an initialroasting in a rotary kiln and subsequentcalcination.

In thisrespecttheintroduction ofstep I)in alternative B allows much of the organic component to be removed, with a significant reduction in gaseous emissions compared to the various processes described in theliteraturewhich havedoubleheattreatment.

Figure 2 showsthe effecton thethermalprofile along thewhole axis ofthe rotary kiln due to the percentage ofthe organiccomponent stillpresenton thewashed catalyst.

Step III-B) involves leaching of the pre-treated and ground catalystasin step II-B).Leachingisperformedwith an alkalinesolution ofwater and sodium hydroxide (H ₂ O-NaOH)with a sodium hydroxide concentration of0.5-4M,atasolid concentration of10-20% foratimeof 2-3hoursatroom temperaturewith orwithoutstirring.Itispossibleto use ozone (O ₃ ) as described for step III-A) to oxidise the metals remaining assulfidesduring step II-B).In thiscase,ozoneisfed tothe leaching reactor in quantities that differ from those in step III-A): additions ofthe reagents are optimised flexibly using redox potential- typesensorsorspecificstandardconditionsmanagedbysoftware.Att he end ofthereaction theresidualsolidisfiltered andwashedwith water.

During roasting,itispossible to inserta complexing agentsuch asa sodium salt(NaHCO ₃ ,Na ₂ CO ₃ ,NaCl,etc.).In thisway,oxidation andcomplexationtakeplacewithintherotarykiln andtheuseofsodium hydroxideduringleachingisnotnecessary.Leachingsimply useswater ata temperatureof85°C (±5°C),ata solid concentration of10-20% fora timeof2-3hours. TheleachingyieldsofV andMofrom theleachingprocessin step III-A) are about 90% for both elements. For the leaching process described in step III-B),a leaching yield ofabout 99% is achieved for both elements.

The precipitation processdescribed in Step IV)forthetreatment ofLCF, combined with the extraction described in Step VIII),makesit possibletorecoverabout95% ofV with apurity ofabout80% and about 95% ofMowith apurity of70%.

The furnacein step II-B)maybeofdifferenttypes.However,itis preferabletouse a rotary kiln forgreaterefficiency in oxygenation and complexation ofthe solid phase.The furnace may be either electric or fuel-fired;in the case of a fuel-fired furnace, a configuration using hydrogen rather than methane hasbeen considered to further reduce the gaseousemissionsrelatedtothisthermalstep.

In a preferred aspect the process according to the invention is carried outatatemperaturenotexceeding60°C.

Alltheprocesssolutionsproposed through thepresentinvention are more economicaland have less impact on the environment than many inventionsin theliterature.Theproposed processisvery flexible and can easily be adapted to different types ofwaste without major modificationstotheprocessschemeandplantlayout:

A.Washing isperformed with acetone,according to the invention.

The latterhasalow boilingpointand solventrecovery iseasier.

B.Washing improves calcining kiln management with better thermalprofiles.

C.The roastingprocessisperformed eitherby meansofan electric oven orusingH ₂ from renewablesources.

D.The process may also be performed without roasting. With roasting,the first leaching is with caustic soda only;without roasting,leaching involvesthe use ofNaOH and H ₂ O ₂ ,possibly with ozone(O ₃ )insteadoforin combination with H ₂ O ₂ .

E.The processisflexiblefordifferenttypesofmaterialscontaining similarchemicalspecies.

F.Not only catalystsfrom thepetrochemicalindustrybutalso those from thepharmaceuticalindustry aretreated. G.Use of ammonium sulfate to precipitate vanadium. This substitution improves the aqueous treatment that can be performedwith lime.

H.Use ofpolyamine toprecipitate molybdenum,which takesplace atroom temperatureinsteadof90°C.

I. Some ofthespentwater (50-80%)may bereused toperform the leachingprocessagain.Theadvantageislesswatertobedisposed of and further recovery of metals of interest that escape the process.

J. Niand Coareselectively recoveredby acidleaching.

EXAMPLES Example 1 TreatmentofspentLCF

150 g ofspentLCF was immersed in 750 mlacetone (20% w/v solid-liquid ratio) for 20 min at room temperature and atmospheric pressure.Afterwashing,thespentsolventwasseparatedfrom thesolid phaseby filtration andthe solidwaswashedwith watera second time. Forthispurpose,the solid wasimmersed in 750 mlofwaterunderthe same conditionsasforthefirstwash and filtration wasperformed after afew minutes.

The washed solid wasdried in airand a weightlossofabout8% was estimated.Subsequently,the solid was ground using a planetary mill with a stainless steel container and metal balls to reduce the particlesizebelow 200 pm.Themillwasprogrammed ata speed of600 rpm for10minutes.

4 gLCF treated asdescribed abovewasimmersed in 40mlofan alkaline solution (10% w/v solid-liquid ratio)containing 3.2 g NaOH (2M) and 8.24mlH ₂ O ₂ at30% w/v.(2M).

Sodium hydroxide was added at the start of the test while hydrogen peroxide was added in 3 steps so as to limit the gradual degradation of the oxidant and ensure an excess of the reagent throughoutthereaction time.

Theleachingreaction wasconducted atroom temperatureand at atmosphericpressure for about3 hourswithoutstirring.The residual solidwasthen separatedfrom thesolutionbyfiltration andwashedwith 12 mlofwater (30% vol./vol.oftheinitialsolution).The residualsolid was dried in an oven at 60°C for 24 hours and the weight loss was determinedtobeabout27% andthemoisturecontentofthesolidbefore dryingabout30%.

Thefinalsolution andwashwaterwereanalysedtodeterminethe concentrationsofvanadium and molybdenum.Vanadium recovery was achieved with a yield ofabout80% and molybdenum recovery with a yieldofabout85%.

With a secondleachingstageand across-currentconfiguration it ispossibletorecoverboth elementswithleachingyieldsinexcessof90%.

Selectiveprecipitation ofthetwoelementswasconducted in two differentsteps.In thefirststep theleachingsolution wasneutralisedto pH 7.5with HCland NH ₄ CIwasaddedin therange2-3in excessofthe stoichiometricamountrequired forthe reaction with thevanadium in thesolution.

The precipitation reaction was conducted at 40°C and atmosphericpressureforabout2hoursat200rpm.Thesolidprecipitat e was filtered and dried. The recovery yield obtained for vanadium precipitation wasover70%.

Subsequently, selective precipitation of molybdenum was performed.The solution wasneutralised to pH 1.5 by adding HCland about10 mlofpolyamine.Molybdenum recovery atroom temperature was achievedwith ayieldofabout60%.

Example2

TreatmentofMocatalysts

A sample ofMo catalystwasground using a planetary ballmill with a stainless steelcontainer and grinding balls at 600 rpm for 10 minutes.An average diameter ofthe solid particles after grinding of about90m wasdeterminedbythesievingmethod.

Thegroundsolidwasleachedusingasolid-liquidratioof15% w/v. Forthispurpose,7.5 gofground catalystwasimmersed in 50 mlofan alkalineaqueoussolution containing4 gNaOH (1M).

The leaching reaction was conducted at room temperature and atmosphericpressurefor1houratamixingspeed of200rpm. Atthe end ofthe reaction the residualsolid wasseparated from the solution by filtration and washed with 15 mlofwater (30% vol.of theinitialsolution).Theresidualsolidwasdriedin an oven at60°C for 24 hoursand theweightlosswasdetermined tobe about35% and the moisturecontentofthesolidbeforedryingabout34%.

Thefinalsolution andwashwaterwereanalysedtodeterminethe molybdenum concentration. Molybdenum recovery was achieved in excessof95% yield.

The alkaline aqueous solution obtained from the leaching step was subjectedtoaselectivemolybdenum precipitation step.98mlofthe solution obtained as described above was neutralised to pH 1.5 with 7.2 ml of 37% w/w HCl. NH ₄ CI was added to the solution to a concentration of20g/1.

The precipitation reaction was conducted at room temperature andatmosphericpressureforabout30minwith astirringspeedofabout 200 rpm.The solid precipitate was separated from the solution by filtration andwashedwith 12mlofwater.Finally,thesolidprecipitate was driedin an oven at105°C for48hours.

Molybdenum wasrecoveredasmolybdenum trioxideMoO ₃ with a recoveryyield ofover98% and apurity ofabout95%.

Example3

Treatmentofrefiningsludge

15g ofsludgefrom oilrefiningprocesseswastreatedwith 100ml ofan alkaline aqueous solution containing 0.5% vol.of30% w/v H2O2 and NaOH in aratioof0.75:1tothesolidused.

The leaching reaction was conducted for 3 hours at room temperatureand astirringspeed ofapproximately 250rpm.Attheend ofthe reaction,filtration was performed and the residual solid was washedwith 30mlofwater(30% vol/volratioofwashwatertosolution).

Vanadium was recovered in excess of 65% yield in a single leaching stage.An increasein temperatureand hydrogen peroxidewas foundtoincreasetheextraction yield above90%.

Approximately 45mlofthesolution obtainedby mixingtogether theleachingsolution andthewash waterwereneutralisedtopH 7.5by the addition of about 3.5 ml HCl.Approximately 3 g of ammonium chloridewasadded andtheprecipitation reaction wasconducted for30 min.

Vanadium wasrecoveredwith arecovery yieldofover90% and a purity ofabout95%.

Example4

LCF treatmentusingozone

12 g ofLCF,pre-treated by washing with acetone,wastreated with 80 ml(15% w/v solid-liquid ratio)ofan alkaline aqueoussolution containing 0.5% w/v 30% w/v H ₂ O ₂ ,1.64 M NaOH and O ₃ continuously fed forthe duration ofthe test (3 hours)ata flow rate of3 g/h and a concentration of8 mg/1.Ozone wasbubbled directly into the leaching solution for 15 min before addingthe soda ash,hydrogen peroxide and solid.

Atthe end ofthereaction,vacuum filtration wasperformed and theresidualsolid waswashed with 24 mlofwater(30% vol/volratio of wash watertosolution).

Vanadium was recovered in excess of 70% yield in a single leaching stage,whilemolybdenum wasrecoveredin excessof95% yield.

Example 5

WashingofspentLCF with surfactant

100 g of spent LCF was immersed in 200 ml of an aqueous surfactant solution (50% w/v solid-liquid ratio) for 45 minutes at a temperatureof35 °C.Thetestwasconductedwith agitation and using ultrasound.

Attheend ofthewash thesolution wasseparated from thesolid phase by filtration and a second washing ofthe solid with waterwas performed.Forthispurposethesolidwasimmersed in 300mlofwater (33% w/v solid-liquid ratio) and filtration was performed after a few minutes.

The washed solid was dried in air,and a hydrocarbon removal rateof80% and atotalcarbon reduction of30% werecalculated. REFERENCES

[1] US5702500A,1997,Integratedprocessfortherecovery ofmetals and fused alumina from spentcatalysts,Z.R.Llanos,G.F.Provoost, W. G.Deering,F.J.Debaene,GulfChemicalandMetallurgicalCo.

[2] P.Dufresne,2011,Hydroprocessing catalysts regeneration and recycling,Applied CatalysisA:General,Vol.322,Pages67-75.

[3] US4670229,1987,Cyclic Process for Recovery of Metals from SpentCatalysts.Wiewiorowski,E.,Tinnin,R;Cronojevich,R.

[4] JPS62176917A,1987,Separation ofmolybdenum from vanadium, H.Mashima, K.Matsuda,S.Toda.

[5] S. Al-Fulaij, G.R. Gouda,A. Stanislaus, S.Dieb, H.Dashti, H.Ibrahim,Spent CatalystTreatment and Utilization,PET 39 Final Report,KISR 1614,KuwaitInst.ForScientificResearch,Kuwait,1985.

[6] Moxba-Metrex. The Catalyst in Waste Recycling. www .moxba.com

[7] M.V.Wang, 2000,Recyclingofmetalsandengineeringmaterials, in:R.Stewart,R.Stephens,J.C.Daley,TMS (Eds.),The Minerals, MetalsandMaterialsSociety.

[8] AMG Vanadium, Company Profile, https://amg- v.com/sustainability/

[9] https://www.smm.co.ip/EZnews/release/uploaded files/e100122- 2.pdf

[10] GfEMetalleundMaterialenGmBH,Vanadium Sourcingin Terms of Environmental Technologies and Services, https://www.gfe.com/en/products-and-solutions/technologies.

[11] SCR,SpentCatalystRecyclingGmBH,CompanyBrochure,2007. www .spentcat.net/services.htm .

[12] AURAMET, AURA MetallurgicalGmBH,Company Profile,2007, in:www.auramet.de/sp_process.

[13] US82897B2,2012,Process for recovering boehmite and γ-Al ₂ O ₃ from spenthydroprocessing catalysts,M.Marafi,KuwaitInstitute for ScientificResearch.

[14] US8287618B2,2012,Method orprocessforrecoveringMo,V,Ni, Co andAlfrom spentcatalystsusing ultrasonicassisted leachingwith EDTA, M.Marafi,KuwaitInstituteforScientificResearch.

[15] US 2007/025899 Al,Process for metals recovery from spent catalyst,P.J.Marcantonio,Chevron USA Inc.,1 February 2007 (2007- 02-01).

[16] CN105274344A, 2016, Method for recycling vanadium and molybdenum from wastepetroleum catalyst,LIU CHULING,China.

[17] KR 10-1189183,2012,Recovery method ofvaluablemetalsfrom spentcatalyst,Pak J.J.,Kim D.H.,Park C.H.,Paek M.K.,JoJ.O.,Lee K.I., IUCF-HYU (Industry-University Cooperation Foundation Hanyang University)Taiwan.

[18] HyVent.Availableonline: http://www.hyvent.nl/spent%20catalyst.html.