IN MEMORIAM Prof. Dr. Ing. PETRU BALTĂ

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1 Revista Română de Materiale / Romanian Journal of Materials 16, 46 (1), -7 IN MEMORIAM Prof. Dr. Ing. PETRU BALTĂ INERTIZAREA UNOR DEŞEURI SOLIDE, CU CONŢINUT DE METALE GRELE, ÎN LIANŢI MAGNEZIANO-FOSFATICI SOLID WASTE WITH HEAVY METAL CONTENT INERTIZATION IN CHEMICALLY BONDED PHOSPHATE CERAMIC ELENA DUMITRESCU 1, ECATERINA ANDRONESCU 1 OMV PETROM S.A. ICPT Campina, B-dul Culturii, nr. 9, Campina, Jud Prahova, România Universitatea Politehnica Bucureşti, Str. G. Polizu nr.1, sector 1, cod 161, Bucuresti, România This paper presents experimental results for solid waste (with heavy metals content) inertization in chemically bonded phosphate ceramic (CBPC) matrix. This process turns hazardous waste in non-hazardous waste. It was studied the inertization of contaminated soil with heavy metals (Cu, Ni, Pb and Zn) in chemically bonded phosphate ceramic versus inertization in Portland cement paste. Waste load was 5%, 7% and 8%. As the CBPC is a fast setting system, it was also used a retarder (i.e. boric acid and calcium lignosulfonate) in concentration of 1% (based on the amount of magnesium oxide and potassium dihydrogen phosphate). To determine the effectiveness of inertization were performed leaching tests and in acid solution, and the obtained values were compared with limits. All wastes stabilized with portland cement and CBPC meet specific criteria for compressive strength for accepting waste in landfill, but stabilization in CBPC is more effective. In terms of nickel leachability, stabilizing of waste in CBPC allows soil waste loading of 8% compared with those stabilized in cement that allows waste loading of 5%. Lucrarea prezintă rezultatele experimentale pentru inertizarea deşeurilor solide (cu conţinut de metale grele) în lianţi magneziano-fosfatici (CBPC). Prin acest proces deşeurile periculoase se transformă în deşeuri nepericuloase. S-a studiat inertizarea deşeului de sol contaminat cu metale grele (Cu, Ni, Pb şi Zn) în CBPC comparativ cu inertizarea în pasta de ciment portland. Încărcarea în deşeu a fost de 5%, 7% şi 8 %. Deoarece sistemul CBPC este unul cu întărire rapidă, s-au utilizat întârzietori de priză (acid boric şi lignosulfonat de calciu) în concentraţie de 1% (raportat la cantitatea de oxid de magneziu şi fosfat diacid de potasiu). Pentru determinarea eficienţei procesului de inertizare a deşeurilor s-au realizat teste de levigare în apă şi în soluţie acidă, valorile obţinute comparându-se cu cele reglementate. Toate deşeurile stabilizate atât cu ciment portland cât şi cu CBPC îndeplinesc criteriul stabilit pentru rezistenţa la compresiune pentru acceptarea deşeurilor în depozite de deşeuri, dar stabilizarea în CBPC este mai eficientă faţă de stabilizarea în ciment. Din punct de vedere al levigabilităţii nichelului în apă,, stabilizarea cu CBPC permite încărcări în deşeu de 8%, faţă de stabilizarea în ciment care permite o încărcare de 5%. Keywords: waste inertization, contaminated soil, heavy metals, chemically bonded phosphate ceramic, portland cement, leachate. 1. Introduction Wastes are generated in a wide variety of chemical and physical forms. They must be stabilized in a physically and chemically stable form, and stored in a manner that minimizes the need for safety and control systems, maintenance, monitoring and human intervention. The processes of stabilization are suitable for treatment of difficult wastes. It is one of the most used techniques because it is relatively simple, inexpensive and efficient. For encapsulation of hazardous constituents may be used different matrix materials [1, ]: cement, phosphatic materials or various binders. Chemically bonded phosphate ceramics (CBPC) are formed through acid-base reaction between phosphate acid or phosphate salts and magnesium oxide. This material is unique because it is formed at room temperature as a portland cement, but has proprieties (i.e mechanical strength) of heat treated ceramic. CBPC can incorporate waste into a crystalline matrix, tough solid with low permeability and good long-term durability. It is an inexpensive means of incorporating waste at low temperature in a crystalline form. During formation of CBPC, inorganic contaminants from waste are converted to phosphates. At the same time, they are physically encapsulated in dense phosphate matrix. This dual mechanism of chemical immobilization and physical encapsulation is very efficient. CBPC presents advantages over inertization in Portland cement: - allows a maximum load in waste up to 7% (wt %) as compared with portland cement which allows Autor corespondent/corresponding author, elena.dumitrescu@petrom.ro

2 E. Dumitrescu, E. Andronescu / Inertizarea unor deşeuri solide, cu conţinut de metale grele, în lianţi magneziano-fosfatici 3 lower loading in the waste [, 3] - allows a salts (e.g. nitrates, chlorides, sulfates) loading of maximum 4% (3 times greater than cement) [4] To obtain CBPC, MgO must be calcined at temperatures above C in order to delay reactivity and then it must be slightly graded in order to crumble the agglomerated particles [5]. If the reaction is too fast, it produces a precipitate and not a ceramic material. Because of this reason retarders must be used retarders such as boric acid (H 3 BO 3 ) [6] or calcium lignosulfonate (LSC).. Experimental It was prepared a quantity of 3 kg of uncontaminated soil polluted in the laboratory with (.%) heavy metals (Cu, Ni, Pb, Zn - 5 of each). Metals were added as salts: CuCl *H O; Ni(NO 3 ) *6H O,Pb(NO 3 ) ;Zn(CH 3 COO) *H O. For a good mixing, soil was prepared as soil saturated paste by adding distilled water until it reaches the saturated paste features [7,8]: - the surface of paste shines - when slope the container, the soil paste flows easily - do not accumulate water at surface - when making a dent with spatula, the soil paste gently flowing in the formed ditch. It was determined the saturation percentage (SP) for soil paste with the formula SP = (mass of water/mass of dried soil) * (%); in our case SP= 4%..1. Preparation of waste samples stabilized with cement The waste samples stabilized with cement CEM II/A-LL 4.5R) were prepared as follows: over the soil waste contaminated with metals ( ) prepared as a soil saturated paste was added the quantities of cement and water according to Table 1. For a waste loading of 5% it was added equal amounts of contaminated soil and cement. For a waste loading of 7% it were mixed 7% contaminated soil with 3% cement and for a waste loading of 8% it were mixed 8% contaminated soil with % cement. Water was added in small portions, alternating with cement, under continuous mixing with a mixer and then the samples were poured into cubic forms with 5 cm sides... Waste samples stabilized with CBPC The waste samples stabilized with phosphate ceramics are prepared as follows: over the soil waste contaminated with metals ( ) prepared as a soil saturated paste it was added water according to Table and then retarders (boric acid and LSC), followed by KH PO 4 and MgO. Magnesium oxide p.a. was previously calcined at 1 C for 3 hours. Retarders were used in proportion of 1% reported at MgO+KH PO 4 mixture. After adding each substance the mixing was performed for 3 minutes with an electric mixer at about 15 rotation per minute. s had the consistency of a fluid paste. Then samples were poured into cubic forms with 5 cm sides without further compaction. The samples were allowed to harden in metallic formwork for days at the room temperature and then they were removed and kept also at the room temperature code Codul probei code Codul probei Compositions for samples stabilized with cement / Compoziţia probelor stabilizate cu ciment Quantity of soil Quantity of solid waste Quantity of cement, saturated paste, from saturated paste, Cantitate ciment Cantitatea de Cantitate deşeu solid pastă saturată din pastă saturată Waste loading Încărcarea in deşeu Table 1 Quantity of added water Cantitate de apă adăugată % g g % g % ml Compositions for samples stabilized with CBPC/Compoziţia probelor stabilizate cu CBPC Waste Quantity of Quantity of solid waste MgO KH PO 4 H 3 BO 3 LSC Total loading soil saturated from saturated paste, MgO+KH PO 4 + Încărcarea paste, Cantitate deşeu solid H 3 BO 3 +LSC în deşeu Cantitatea de din pasta saturată pastă saturată % g g % g g g g g % ml A B C Water Apă Table

3 4 E. Dumitrescu, E. Andronescu / Solid waste with heavy metal content inertization in chemically bonded phosphate ceramic.3. Unconfined compressive strength Unconfined compressive strength was measured to establish the cohesiveness of the materials. It also represents the effectiveness of the solidification and stabilization of the binder with the waste. The compressive strength was determined after 3 days of hardening on samples with surface of 5 cm. It was used a press HECKERT FP /1 and were measured two samples for each composition. According to the United States Environmental Protection Agency (USEPA) [9] regulations, solidified and stabilized waste products must have a minimum unconfined compressive strength of 5 psi (.35 MPa) after 8 days..4. Leachate Test Results (solid: water ratio = 1:) After 3 days from sample preparation it was performed the leaching test for a ratio stabilized solid: water = 1: according to STAS SR EN :3 []. The stabilized solid waste was crushed until particle became smaller than mm (the crushed sample was sieved and particulates higher than mm still need to be grinded to become smaller than mm) and then was mixed with distillated water. The obtained suspension was stirred for 4 hours on an orbital shaker at rotation per minute then it was filtered and preserved with HNO 3 to ph < for metals analysis. Analyses for determination of metals in leachate were performed by inductively coupled plasma spectrometry (ICP)..5. Toxicity characteristic leaching procedure TCLP EPA Method 1311 After 3 days the samples were also submitted to TCLP leaching procedure [11]. In order to carry out this procedure can be used one from the following extraction fluids: - Fluid 1: add 5.7 ml glacial acetic acid to 5 ml distilled water, add 64.3 ml of 1N NaOH and dilute to a volume of 1 liter with distilled water. ph of this solution is Fluid : dilute 5.7 ml glacial acetic acid with distilled water to a volume of 1 liter. ph of this solution is To determine which of the two extraction fluids should be proceed as follows: - weigh out 5 g solid waste with particle size of approximate 1 mm in a 5 ml Erlenmeyer flask and then add 96.5 ml distilled water - cover with a watch glass and stir vigorously for 5 minutes using a magnetic stirrer: - measure and record ph; - if the ph is lower than 5, it is used extraction fluid 1; - if the ph is greater than 5, add 3.5 ml of 1N HCl, mix, cover with a watch glass, heat to 5 C and maintained at this temperature for minutes. Cool at room temperature and measure the ph; - if the ph is less than 5, it is used extraction fluid 1; - if the ph is greater than 5 is used extraction fluid. 3. Results and disscussions The compressive strength values obtained on these compositions after 3 days of hardening are shown in Table 3. Table 3 Compressive strength of the samples after 3 days Rezistenţa la compresiune după 3 de zile code Codul probei composition Compoziţia probei Compressive strength, MPa Rezistenţa la compresiune 1 5% waste 4.7 7% waste % waste.6 A 5% waste 9.9 B 7% waste 3.53 C 8% waste 1.78 According to USEPA criterion, all wastes stabilized with cement or CBPC meet the specification, but those stabilized with CBPC are more suitable to support loads placed on them in the landfill. As the stabilized waste is more resistant, even stabilization process is more efficient. Unconfined compressive strength decrease with increasing of soil waste percentage in the final stabilized product because decreases the binding agent quantity used. In Figures 1-4 are presented the metals in leachate (values are expressed in ) versus the maximum of Cu, Ni, Pb or Zn in leachate. The maximum values for leachate 1: (solid: liquid) in distilled water - expressed in solid waste - according to Order 95/5 [1], are presented in Table 4. According to results obtained for water the stabilized soil wastes are classified as follow: - Wastes stabilized with portland cement: o for Cu all soil stabilized wastes (waste loading up to 8%) are non-hazardous o for Ni soil waste stabilized with cement (waste loading 5%) are non-hazardous, but those with waste loading 7% and 8% are hazardous o for Pb and Zn all soil stabilized wastes (waste loading up to 8%) are inert

4 E. Dumitrescu, E. Andronescu / Inertizarea unor deşeuri solide, cu conţinut de metale grele, în lianţi magneziano-fosfatici 5 Cu % waste 11 7% waste 19 8% waste Non Hazardous waste 5% waste 18 7% waste 11 8% waste Cu Nonhazardous waste Fig. 1 - Cu concentration leachate versus the maximum of Cu in leachate [1] Concentraţia de Cu în levigatul în apă comparativ cu concentraţia maximă admisă [1]. Ni % waste Non hazardous waste 7% waste 8% waste Hazardous waste.8 5% waste % waste 8% waste Ni Nonhazardous waste Fig. - Ni concentration leachate versus the maximum of Ni in leachate [1] Concentraţia de Ni în levigatul în apă comparativ cu concentraţia maximă admisă [1]. Pb % waste 7% waste 8% waste Non hazardous waste.5 5% waste % waste 8% waste Pb Nonhazardous waste Fig. 3 - Pb concentration leachate versus the maximum of Pb in leachate [1] Concentraţia de Pb în levigatul în apă comparativ cu concentraţia maximă admisă [1]. Zn % waste 7% waste 8% waste inert waste.9 5% waste 7% waste 1.8 8% waste Zn Fig. 4 - Zn concentration leachate versus the maximum of Zn in leachate [1] Concentraţia de Zn în levigatul în apă comparativ cu concentraţia maximă admisă [1].

5 6 E. Dumitrescu, E. Andronescu / Solid waste with heavy metal content inertization in chemically bonded phosphate ceramic The maximum of metals in leachate / Concentraţia de metale maximă admisă în levigat Metals, Waste classification Metale, Clasificare deşeu Cu Ni Pb Zn Deşeu inert Non-hazardous waste Deşeu nepericulos 5 5 Hazardous waste that may be classified as non-hazardous Deşeu periculos care poate fi 5 5 clasificat ca nepericulos Hazardous waste Deşeu periculos Wastes stabilized with CBPC: o for Cu all soil wastes stabilized (waste loading up to 8%) are non-hazardous o for Ni all soil wastes stabilized are nonhazardous o for Pb waste stabilized with CBPC (waste loading 5%) is inert and those with higher waste loading (7%, 8%) are nonhazardous o for Zn all stabilized wastes (waste loading up to 8%) are inert ph for: 5g solid ml distillate water ph pentru: 5g solid ml apă distilată ph after adding of 3.5 ml 1 N HCl ph după adăugarea a 3.5 ml HCl 1N Metal Table 4 For TCLP procedure, ph values necessary to establishing the extraction fluid (after adding distilled water and after adding 1N HCl) are presented in table 5. For all samples the ph is greater Than 5 after the addition of 1N HCl therefore it was used the extraction fluid. The analysis results for TCLP extract using extraction fluid, performed by ICP-OES, are presented in the Tables 6 and 7 (values are expressed in ). Regulated limits for TCLP procedure [13] are presented in Table 8. ph values for establishing of extraction fluid / Valorile ph-ului pentru stabilirea fluidului de extracţie 5% waste ciment + 5% deşeu 7% waste ciment + 7% deşeu 8% waste ciment + 8% deşeu 5% waste 5% deşeu 7% waste 7% deşeu 8% waste 8% deşeu Metal in TCLP extract for waste inerted in cement Concentraţiile de metale in extractul TCLP pentru deşeu inertizat in ciment 7% waste, ciment + 7% deşeu 5% waste, ciment + 5% deşeu 8% waste, ciment + 8% deşeu Cu Ni Pb <.1.1. Zn Table 5 Table 6 Table 7 Metal in TCLP extract for waste inerted in CBPC / Concentraţiile de metale in extractul TCLP pentru deşeu inertizat în CBPC Metal 5% waste, 5% deşeu, 7% waste, 5% deşeu, 8% waste, 5% deşeu, Cu..4.5 Ni Pbl < Zn Table 8 Regulated limits for TCLP procedure, values are expressed in / Valori maxime admise pentru procedura TCLP, valori exprimate în Metal Maximum allowable TCLP extract, according EPA and Onyx Waste Acceptance Landfilling Protocol / Concentraţia maximă admisă pentru extractul TCLP, conform EPA şi protocolului Onyx de acceptare în depozitul de deşeuri Cu Ni 35 Pb 5 Zn 5

6 E. Dumitrescu, E. Andronescu / Inertizarea unor deşeuri solide, cu conţinut de metale grele, în lianţi magneziano-fosfatici 7 According to results obtained for TCLP extract, all soil waste stabilized with cement and CBPC presents values below maximum allowable concentration. 4. Conclusions Based on the results obtained in this study, for Cu, all wastes stabilized with both CBPC and cement can be classified as non-hazardous. For Ni, waste stabilized with cement (with 5% load in contaminated soil) is classified as nonhazardous, but wastes stabilized with cement (with 7% and 8% load in soil contaminated) are classified as hazardous. All wastes with Ni stabilized with CBPC are non-hazardous. For Pb all wastes stabilized with cement are considered inert. Wastes stabilized in CBPC, with 5% load in contaminated soil, are inert and those with 7 and 8% load in contaminated soil are nonhazardous. For Zn all wastes stabilized with both CBPC and cement are classified as inert. In terms of compressive strength all wastes stabilized with cement or CBPC meet the criteria to have a minimum unconfined compressive strength of 5 psi (.35 MPa) after 8 days. Soil waste stabilized with CBPC presents two times higher values than those stabilized with cement, therefore stabilization in CBPC is more effective from this point of view. In terms of leachability for wastes with Ni, CBPC allows a waste load up to 8 %, while cement allows a maximum load of 5% in solid waste. In terms of leachability for Cu, Pb and Zn both cement and CBPC allow loading in soil contaminated waste up to 8%, the stabilized waste resulted is inert or non-hazardous. In terms of leachability according to TCLP procedure, all wastes stabilized with both CBPC and cement are below the maximum allowable for Cu, Ni, Pb and Zn. The soil wastes stabilized with CBPC are more suitable to support loads placed on them in the landfill and are more durable in time. CBPC allows a loading in soil waste up to 8% for Ni, while the cement permits a loading of only 5%. For Cu, Pb, Zn both cement and CBPC allow a soil waste loading up 8%. REFERENCES 1. Ion Teoreanu, Nicoleta Deneanu and Mirela Dulamă, Matrix materials for the conditioning organic radioactive wastes, Romanian Journal of Materials, 4().. Sandip Chattopadhyay, Evaluation of Chemically Bonded Phosphate ceramics for Mercury Stabilization of a Mixed Syntetic waste, National Risk management research Laboratory, USEPA, Dileep Singh and Kartikey Patel, Modified Phosphate Ceramics for Stabilization and Solidification of Salt Mixed Wastes, Energy Technology Division, Aragonne National Laboratory, U.S. Department of Energy, Stabilization using Phosphate Bonded Ceramics, Salt containing mixed waste treatment, Mixed waste focus area, Arun S. Wagh and Dileep Singh, Chemically Bonded Phosphate Ceramics for Stabilization and Solidification of Mixed Waste, Energy Technology Division, Aragonne Naltional Laboratory 6. Arun S. Wagh, Chemically Bonded Phosphate Ceramics, Twenty-first century materials with divers applications, Aragonne National Laboratory, M.R. Carter and E.G. Gregorich, Soil Sampling and Methods of Analysis, 15. Extraction Saturation Extract, Canadian Society of Soil Science, second edition, Radu Lăcătuşu and Nineta Rizea, Chemical and microbiological analysis methods (used in soil monitoring system), Chaper VII. Determination of soluble salts from soil. Obtaining of aqueous extract at saturation from soil, USEPA OSWER Directive A, USEPA STAS SR EN :3 Part 4: Characterisation of waste - Leaching - Compliance test for leaching of granular waste materials and sludges - Part 4: One stage batch test at a liquid to solid ratio of l/kg for materials with particle size below mm (without or with size reduction). 11. Environmental Protection Agency, EPA, Method 1311 Toxicity Characteristic Leaching Procedure. 1. Order 95/5 Government of Romania Ministry of Environment and Water Management Order for establishing the acceptance criteria and preliminary waste acceptance procedures at storage and the national list of waste accepted in each class of waste deposit. 13. Environmental Protection Agency, EPA, Onyx Waste Acceptance Analytical testing Protocols, 6. ***************************************************************************************************************