Adsorption of Sudan-IV contained in oily wastewater on lipophilic activated carbons: kinetic and isotherm modelling

Up to nine kinetic and fourteen isotherm adsorption models are employed to model the adsorption of Sudan IV, a lipophilic model pollutant present in a biphasic mixture of cyclohexane-water system to simulate oily wastewater. Six different modified activated carbons were used as adsorbents. The highest amount adsorbed of Sudan IV was found in the material prepared by successive treatments of the parent commercial activated carbon Norit ROX 0.8 with nitric acid and urea, followed by thermal treatment at 800 °C under continuous flow of nitrogen. Kinetic and isotherm adsorption models can be employed to simulate the process, since the effect of the presence of water in the adsorption of Sudan IV from the cyclohexane phase was found to be negligible, owing to the high lipophilic character of both adsorbent and adsorbate. All kinetic and isotherm coefficients, coupling with statistical parameters (r2, adjusted r2 and sum of squared errors), are determined by non-linear regression fitting and compared to literature data. The model of Avrami is found to be the most appropriate model to represent the adsorption of the pollutant in any of the six modified carbons tested, the highest value of the kinetic constant being 0.055 min−1. The isotherm adsorption is wellmodelled by using the general isotherm equation of Tóth and the multilayer Jovanović expression for the adsorption of Sudan-IV on that material, resulting in a high monolayer uptake capacity (qm = 193.6 mg g−1).Up to nine kinetic and fourteen isotherm adsorption models are employed to model the adsorption of Sudan IV, a lipophilic model pollutant present in a biphasic mixture of cyclohexane-water system to simulate oily wastewater. Six different modified activated carbons were used as adsorbents. The highest amount adsorbed of Sudan IV was found in the material prepared by successive treatments of the parent commercial activated carbon Norit ROX 0.8 with nitric acid and urea, followed by thermal treatment at 800 °C under continuous flow of nitrogen. Kinetic and isotherm adsorption models can be employed to simulate the process, since the effect of the presence of water in the adsorption of Sudan IV from the cyclohexane phase was found to be negligible, owing to the high lipophilic character of both adsorbent and adsorbate. All kinetic and isotherm coefficients, coupling with statistical parameters (r2, adjusted r2 and sum of squared errors), are determined by non-linear regression fitting and compared to literature data. The model of Avrami is found to be the most appropriate model to represent the adsorption of the pollutant in any of the six modified carbons tested, the highest value of the kinetic constant being 0.055 min−1. The isotherm adsorption is wellmodelled by using the general isotherm equation of Tóth and the multilayer Jovanović expression for the adsorption of Sudan-IV on that material, resulting in a high monolayer uptake capacity (qm = 193.6 mg g−1).This work is a result of Project “AIProcMat@N2020—Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020,” with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); Associate Laboratory LSRE-LCM UID/EQU/50020/2019 funded by national funds through FCT/MCTES (PIDDAC); and CIMO UIDB/00690/2020 through FEDER under Program PT2020.This work i s a re s u l t of Project “AIProcMat@N2020—Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020,” with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); Associate Laboratory LSRE-LCM (UID/ EQU/50020/2019) funded by national funds through FCT/MCTES (PIDDAC); and CIMO (UIDB/00690/2020) through FEDER under Program PT2020.info:eu-repo/semantics/publishedVersio

Removal of Sudan IV from a simulated biphasic oily wastewater by using lipophilic carbon adsorbents

Several chemically and thermally modified activated carbons were tested in the adsorption of a lipophilic pollutant (Sudan IV) contained in biphasic oil-water mixture mimicking petroleum refinery effluents. The effect of different parameters on the adsorption performance has been assessed, such as the absence of water, particle size of the carbon material and the respective chemical and thermal modifications, initial concentration of pollutant, water/oil volume ratio, nature of the organic phase (cyclohexane, n-hexane or n-hexadecane) and the presence of an emulsifier (sodium dodecyl sulphate). Lipophilicity of the adsorbent was found to be a key parameter in the purification of the organic phase. Successive treatments of the parent commercial activated carbon Norit ROX 0.8, namely with nitric acid, urea, followed by a thermal treatment at 800 °C under inert atmosphere, developed the highest adsorption capacity (qe=200 mg·g−1) in the base material. A load of 2.5 g·L−1 of this modified carbon was able to completely remove 500 mg·L−1 of the pollutant from the organic phase after 8 h of contact time, owing to the highest specific surface area (SBET=1055m2·g−1) and characteristic surface chemistry with the lowest content of oxygen surface groups among the tested adsorbents.info:eu-repo/semantics/publishedVersio

Preparation and characterization of natural and pillared clays for catalytic wet peroxide oxidation of 4-nitrophenol

This work deals with the evaluation of two natural clays (NCs) extracted from Karatau (KNC) and Akzhar (ANC) deposits (located in the Zhambyl region of Kazakhstan) to prepare pillared clays (PILCs) for catalytic wet peroxide oxidation (CWPO) of 4-nitrophenol (4-NP), used as model pollutant. NCs were washed with HCl 1 M and then pillared using a solution containing Fe, Cu and Zr. NCs and PILCs were characterized by Electron Microprobe (EMP), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM), as detailed elsewhere [1,2]. EMP confirms the cation exchange of the Ca contained in the NCs (Ca > 15%) in the form of calcite (according to DRX and FTIR), by polycations of the pillaring solution (Ca < 2% for the PILCs). TEM reveals that the impregnation of polycations on the washed NCs also take place, coupling with its pillarization. CWPO runs were performed following the methodology and operational conditions described in previous works [1,2]. All materials show catalytic activity, since the H2O2 is consumed (Fig. 1A) to oxidize the 4-NP. Both KPILC and APILC, prepared from KNC and ANC, respectively, allow the complete removal of 4-NP after 4 h, whereas the conversion of 4-NP was less than 20% with the NCs (Fig. 1B). TOC conversions higher than 60 % were achieved with PILCs after 8 h. The subtraction of the theoretical TOC contribution of 4-NP from experimental TOC allowed to observe the formation of oxidazable intermediate compounds (maximum value of TOCexperimental- TOC4-NP at 1 h of reaction), which are oxidized to form refractory products (Fig. 1C). Based on these contributions of the TOC, a kinetic model based on TOC lumping into three blocks (TOCA à TOCB à TOCC, corresponding to the initial TOC of 4-NP, oxidazable intermediates and refractory products, respectively) was developed for the NCs and PILCs, predicting suitably the evolution of 4-NP, H2O2 and TOC in the CWPO of 4-NP (Fig. 1).This work is a result of project “AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145- FEDER-000006, supported by NORTE 2020, under the Portugal 2020 Partnership Agreement, through FEDER and of Project POCI-01-0145-FEDER-006984 – Associate Laboratory LSRE-LCM funded by FEDER through COMPETE2020 - POCI – and by national funds through FCT.info:eu-repo/semantics/publishedVersio

Condensation by-products in wet peroxide oxidation: Fouling or catalytic promotion? Part II: Activity, nature and stability

The deposition of condensation by-products onto the catalyst surface upon wet peroxide and wet air oxidation processes has usually been associated with catalyst deactivation. However, in Part I of this paper, it was demonstrated that these carbonaceous deposits actually act as catalytic promoters in the oxygen-assisted wet peroxide oxidation (WPO-O2) of phenol. Herein, the intrinsic activity, nature and stability of these species have been investigated. To achieve this goal, an up-flow fixed bed reactor packed with porous Al2O3 spheres was used to facilitate the deposition of the condensation by-products formed in the liquid phase. It was demonstrated that the condensation by-products catalyzed the decomposition of H2O2 and a higher amount of these species leads to a higher degree of oxidation degree The reaction rates, conversion values and intermediates’ distribution were analyzed. The characterization of the carbonaceous deposits on the Al2O3 spheres showed a significant amount of condensation by-products (~6 wt.%) after 650 h of time on stream. They are of aromatic nature and present oxygen functional groups consisting of quinones, phenols, aldehydes, carboxylics and ketones. The initial phenol concentration and H2O2 dose were found to be crucial variables for the generation and consumption of such species, respectively.This research was supported by the Spanish MINECO through the project CTM-2016-76454-R and by the CM through the project P2018/EMT-4341. M. Munoz thanks the Spanish MINECO for the Ramón y Cajal postdoctoral contract (RYC-2016-20648).info:eu-repo/semantics/publishedVersio

Condensation by-products in wet peroxide oxidation: Fouling or catalytic promotion? Part I: Evidences of an autocatalytic process

The deposition of condensation by-products onto the catalyst surface upon wet peroxide and wet air oxidation processes has usually been associated with catalyst deactivation. However, in Part I of this paper, it was demonstrated that these carbonaceous deposits actually act as catalytic promoters in the oxygen-assisted wet peroxide oxidation (WPO-O2) of phenol. Herein, the intrinsic activity, nature and stability of these species have been investigated. To achieve this goal, an up-flow fixed bed reactor packed with porous Al2O3 spheres was used to facilitate the deposition of the condensation by-products formed in the liquid phase. It was demonstrated that the condensation by-products catalyzed the decomposition of H2O2 and a higher amount of these species leads to a higher degree of oxidation degree The reaction rates, conversion values and intermediates’ distribution were analyzed. The characterization of the carbonaceous deposits on the Al2O3 spheres showed a significant amount of condensation by-products (~6 wt.%) after 650 h of time on stream. They are of aromatic nature and present oxygen functional groups consisting of quinones, phenols, aldehydes, carboxylics and ketones. The initial phenol concentration and H2O2 dose were found to be crucial variables for the generation and consumption of such species, respectivelyThis research was supported by the Spanish MINECO through the project CTM-2016-76454-R and by the CM through the project P2018/EMT-4341. M. Munoz thanks the Spanish MINECO for the Ramón y Cajal postdoctoral contract (RYC-2016-20648).info:eu-repo/semantics/publishedVersio

Synthesis and characterization of clay-based catalysts prepared from natural clays

This work deals with the synthesis and characterization of clay-based catalysts. The catalysts prepared in this work were clays activated through acid treatment and clays pillared with Co and Fe. For the preparation, natural clays from four different regions of Kazakhstan were used: Akzhar, Asa, Karatau and Kokshetau. The FTIR analysis showed that the pillared clays have an amount of iron in its structure. The N2 adsorption isotherms obtained were classified as Type II, according to IUPAC classification, typical of macroporous materials. The SBET calculated with the N2 adsorption isotherms for the activated clays showed to be higher than the SBET results for natural clays. XRD patterns helped to gather information about crystalline phases of the clay, allows classifying the type of clay used in the work. The acid characterization showed that the procedures used for the preparation of the acid activated clays and pillared clays caused structural modifications, which is another result that suggests the success of both methods.This work is a result of the Project “AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER-000006, supported by ERDF; the CIMO - UID/AGR/00690/2019 – funded by FCT and FEDER under Programme PT2020and the Associate Laboratory LSRE-LCM - UID/EQU/50020/2019 - funded by national funds through FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Simulation and optimization of the CWPO process by combination of aspen plus and 6-factor doehlert matrix: Towards autothermal operation

This work aims to present an industrial perspective on CatalyticWet Peroxide Oxidation (CWPO) technology. Herein, process simulation and experimental design have been coupled to study the optimal process conditions to ensure high-performance oxidation, minimum H2O2 consumption and maximum energetic effciency in an industrial scale CWPO unit. The CWPO of phenol in the presence of carbon black catalysts was studied as a model process in the Aspen Plus® v11 simulator. The kinetic model implemented, based on 30 kinetic equations with 11 organic compounds and H2O2 involvement, was valid to describe the complex reaction network and to reproduce the experimental results. The computer experiments were designed on a six-factor Doehlert Matrix in order to describe the influence of the operating conditions (i.e., the different process temperatures, inlet chemical oxygen demands, doses of H2O2 and space time) on each selected output response (conversion, e ciency of H2O2 consumption and energetic effciency) by a quadratic model. The optimization of the WPO performance by a multi-criteria function highlighted the inlet chemical oxygen demand as the most influential operating condition. It needed to have values between 9.5 and 24 g L-1 for autothermal operation to be sustained under mild operating conditions (reaction temperature: 93–130 ºC and pressure: 1–4 atm) and with a stoichiometric dose of H2O2.The authors thank the financial support by the Spanish Government and Comunidad de Madrid through the projects CTM2016-76454-R and S2018/EMT-4341, respectively. Also, the authors acknowledge financial support to the Portugal Government through the project UIDB/00690/2020.info:eu-repo/semantics/publishedVersio

Catalytic conversion of caffeine into molecules of valuable interest via N-demethylation reaction

This work aims to apply catalytic processes to promote the conversion of caffeine into valuable dimethylxanthines via N-demethylation reaction. Thus, we seek to evaluate the products formed and propose the reactions involved and their mechanisms. Reaction conditions were evaluated including different concentrations of Fenton reagent and ascorbic acid to evaluate caffeine oxidation. Theobromine, paraxanthine, and theophylline formation was proven by HPLC-DAD and mass spectrometry analysis evidencing the N-demethylation reactions, via radicals, with about 1 % yield. These results open the way for new N-demethylation reaction routes to be studied with applications for caffeine and other biomolecules in diverse areas such as biochemistry and medicinal chemistry. Application of the Fenton catalysis as alternative to promote the conversion of caffeine in other xanthines by N-demethylation. In this scenario was verified the capability of ascorbic acid in promoting same reaction, both environmentally friendly processes. This work investigates the possibility of using a well known biocompound as a precursor to obtain value added molecules.This study was financially supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 and by CIMO (UIDB/00690/2020) through FEDER under Program PT2020. In addition, the authors acknowledge Central de Análise e Prospecção Química – CAPQ and Laboratório Central de Biologia Molecular (LCBM), Chemistry Department/UFLA for their technical support. Jose L. Diaz De Tuesta acknowledges the financial support through the program of Atracción al Talento of Comunidad de Madrid (Spain) for the individual research grant 2022-T1/AMB-23946.info:eu-repo/semantics/publishedVersio

Pillared clays from natural resources as catalysts for catalytic wet peroxide oxidation: Characterization and kinetic insights

Pillared clays with Zr and Fe/Cu/Zr polycations have been prepared from natural clays found in large deposits of Kazakhstan and assessed as catalysts for the catalytic wet peroxide oxidation (CWPO), using 4-nitrophenol (4-NP) as model compound. The performance of the catalysts was followed by measuring the concentration of 4-NP, H2O2 and the total organic carbon (TOC), considering C4-NP = 5 g L-1, CH2O2 = 17.8 g L-1, Ccat = 2.5 g L-1, initial pH = 3.0 and T = 50°C. At those selected conditions, the pillared clays showed higher activity than natural clays in the CWPO of 4-NP. The conversion of the model pollutant was complete when Fe/Cu/Zr-PILCs were used, with the TOC removal reaching 78.4% after 24 h with the best Fe/Cu/Zr-PILC. The H2O2, 4-NP and TOC time-evolution was well described by a kinetic model based on TOC lumps in three blocks, considering the initial TOC (corresponding to 4-NP), the production of oxidizable intermediates and the formation of refractory products.This work was financially supported by M.KH. Dulati Taraz State University, through a research work mission carried out in the Associate Laboratory LSRE-LCM, Polytechnic Institute of Bragança, Portugal. This work is also a result of: Project “AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); Associate Laboratory LSRE-LCM-UID/ EQU/50020/2019 – funded by national funds through FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Carbon catalysts derived from compost for wet peroxide oxidation of landfill leachates

O constante crescimento populacional levou a um grande aumento na produção de resíduos sólidos, principalmente resíduos sólidos urbanos (RSU). Uma estratégia ecologicamente correta para gerenciar os RSU é o tratamento mecânico e biológico (TMB). Nas unidades TMB, a fração orgânica dos RSU é tratada, gerando biogás e subprodutos (lixiviado e composto). O composto é ultilizado principalmente como fertilizante agrícola. No entanto, a quantidade de composto produzida é superior à sua procura como fertilizante, criando um excesso de produto. Este trabalho visa a valorização do composto através de carbonização hidrotérmica (CHT), e pirólise, produzindo os catalisadores HC230 e PC800, respectivamente, e sua aplicação na oxidação catalítica com peróxido de hidrogénio (CWPO) do lixiviado gerado na unidade TMB. Os catalisadores foram caracterizados por análise elementar e teor de cinzas. Os ensaios de CWPO do lixiviado (COT = 27 g L-1, DQO = 60 g L-1 e DBO5 = 23 g L-1) foram conduzidos nas seguintes condições operacionais: CCatalisador = 1,8 g L-1; T = 80 ºC; CH2O2 = 85,7 g L-1 e pH de 3,0 a 7,3. A pH = 6, o catalisador HC230 permitiu alcançar uma redução de DQO de 41%, aumentar a razão DBO5/DQO para 0,42, moldando o lixiviado como adequado para tratamento biológico posteriorThe population growth leads to a large increase in solid waste production, notably municipal solid waste (MSW). In this context, the mechanical and biological treatment (MBT) arouses as an environmentally friendly strategy to manage MSW. In MBT plants, the organic fraction of MSW is treated, generating biogas and, as by-products, leachate and compost. The compost is mainly used as an agriculture fertilizer. However, the amount of compost produced is higher than its demand, resulting in excess and accumulation. This work deals with the valorization of compost through hydrothermal carbonization (HTC) and pyrolysis, producing respectively the catalysts HC230 and PC800, and their application in the catalytic wet peroxide oxidation (CWPO) of the leachate waters generated in the MBT plant. The catalysts were characterized by elemental analysis and ash content. The CWPO runs of the leachate waters (TOC = 27 g L-1, COD = 60 g L-1 and BOD5 = 23 g L-1) were conducted under the following operating conditions: CCatalyst = 1.8 g L-1; T = 80 ºC; CH2O2 = 85.7 g L-1 and pH from 3.0 to 7.3. At pH = 6 the HC230 achieved a COD abatement of 41 %, enhancing the BOD5/COD ratio to 0.42, shaping the leachate as suitable for further biological treatmentThis work was financially supported by project “VALORCOMP - Valorización de compost y otros desechos procedentes de la fracción orgánica de los residuos municipales”, with reference 0119_VALORCOMP_2_P, through FEDER under Program INTERREG; Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC); CIMO (UIDB/00690/2020) through FEDER under Program PT2020, and national funding by FCT, Foundation for Science and Technology, and European Social Fund, FSE, through the individual research grant SFRH/BD/143224/2019 of Fernanda Fontana Roman.info:eu-repo/semantics/publishedVersio