Fitting Biochars and Activated Carbons from Residues of the Olive Oil Industry as Supports of FeCatalysts for the Heterogeneous Fenton-Like Treatment of Simulated Olive Mill Wastewater

Bruno Esteves is grateful to FCT for financial support through the PhD grant (SFRH/BD/129235/2017), with financing from National and the European Social Funds through the Human Capital Operational Programme (POCH). Sergio Morales-Torres acknowledges the financial support from the University of Granada (Reincorporación Plan Propio).A series of biochars and activated carbons (ACs) was prepared combining carbonization and physical or chemical activation of cheap and abundant residues of the olive oil industry. These materials were used as Fe-support to develop low-cost catalysts for the heterogeneous Fenton-like oxidation of simulated olive mill wastewater (OMW), the highly pollutant effluent generated by this agroindustry. Commercial ACs were also used as reference. All catalysts prepared were extensively characterized and results related with their performances in the catalytic wet peroxide oxidation (CWPO). Results showed a linear relationship of the textural properties of the catalysts with the adsorptive and catalytic performance, as well as the preferential adsorption and degradation of some phenolic compounds (caffeic and gallic acids) by specific interactions with the catalysts’ surface. Despite the best performance of catalysts developed using commercial supports, those prepared from agro-industrial residues present some advantages, including a smaller catalyst deactivation by iron leaching. CWPO results show that catalysts from physically activated olive stones are the most promising materials, reaching total organic carbon and toxicity reductions of 35% and 60%, respectively, as well an efficient use of H2O2, comparable with those obtained using commercial supports. This approach showed that the optimized treatment of this type of residues will allow their integration in the circular economic process of the olive oil production.Laboratory for Process Engineering, Environment, Biotechnology and Energy-LEPABE - FCT/MCTES (PIDDAC) - European Regional Development Funds (ERDF) through North Portugal Regional Operational Programme (NORTE 2020) UIDB/00511/2020 NORTE-01-0247-FEDER-39789Spanish Project from ERDF/Ministry of Science, Innovation and Universities-State Research Agency RTI2018-099224-B-I0

Integration of catalytic wet peroxidation and membrane distillation processes for olive mill wastewater treatment and water recovery

The degradation of organic matter present in olive mill wastewater (OMW) and the recovery of water were studied by the integration of catalytic wet peroxidation (CWPO) and direct contact membrane distillation (DCMD) for the first time. The oxidation step was performed in a fixed–bed reactor (FBR) working in continuous mode (pH0 = 4.0 ± 0.2, 60 ◦C, Q = 0.75 mL/min, [H2O2]/[COD]feed = 2.3 ± 0.1 g H2O2/g O2). Samples of OMW diluted by 5– and 7.5–fold were used (OMW–5× and OMW–7.5×, respectively), corresponding to inlet chemical oxygen demand (COD) values of 3562 ± 68 and 2335 ± 54 mg/L, total phenolic content (TPh) of 177 ± 17 and 143 ± 7 mg GAeq/L, and total organic carbon (TOC) of 1258 ± 63 and 842 ± 45 mg/L, respectively. The FBR was loaded with 2.0 g of a Fe–activated carbon derived–catalyst, prepared by using olive stones as the precursor, in line with a circular economy model approach. The catalyst was selected based on the activity and stability towards polyphenolic synthetic solutions shown in previous works of the team, while actual OMW samples were used in this work. CWPO–treated samples of OMW allowed the operation of the DCMD unit at higher fluxes than with the analogous untreated ones, also showing higher rejections of organic matter from the feed solution upon DCMD, highlighting the beneficial effect of this novel configuration. Using a pre-treated sample of OMW–7.5× as feed solution (Q = 100 mL/min, Tpermeate ≈ 18 ◦C, Tfeed ≈ 66 ◦C), the produced permeate water stream presented several parameters well–below the legislated thresholds required for direct discharge for crops irrigation, including total suspended solids (TSS < 10 mg/L), TPh (<0.01 mg GAeq/L), biochemical oxygen demand (BOD5 < 40 mg/L), and dissolved Fe (<0.06 mg/L). Moreover, the resulting concentrated OMW–retentate streams could be recirculated to the FBR and maintain the same removal efficiencies obtained previously, despite the increased initial organic loadings of the retentate after DCMD.Portuguese Foundation for Science and Technology LA/P/0045/2020 UIDB/00511/2020 UIDP/00511/2020European Regional Development Funds (ERDF) through North Portugal Regional Operational Programme (NORTE 2020) NORTE-01-0145-FEDER000069NORTE 2020 under the PORTUGAL 2020 Partnership Agreement through ERDF NORTE-01-0145-FEDER000069MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018-099224B-I00Portuguese Foundation for Science and Technology BaseUIDB/50020/2020 UIDP/50020/2020Portuguese Foundation for Science and TechnologyEuropean Commission SFRH/BD/129235/2017National and the European Social Funds through the Human Capital Operational Programme (POCH) MCIN/AEI RYC-2019026634IEuropean Social Found (FSE) "El FSE invierte en tu futuro" RYC-2019026634

Specific adsorbents for the treatment of OMW phenolic compounds by activation of bio-residues from the olive oil industry

A series of adsorbents was developed by physical (CO2) and chemical (KOH) activation of two bio-residues: olive stones (OS) and wood from olive tree pruning (OTP). The physicochemical properties of such materials were determined and correlated with their adsorptive performance in the removal of phenolic compounds of olive mill wastewater (OMW). Adsorption isotherms and kinetics of single phenolic acids, as well as the kinetics for competitive multi-compound adsorption, were fitted by applying different models, though Langmuir and pseudosecond order models fitted better the experimental results, respectively. The intraparticle diffusion model pointed out that mesoporosity reduces the influence of phenolic compounds' restrictions in the external film diffusion of the adsorbent particle-solution interphase, but adsorption capacity linearly increases with the micropore volume accessible to N-2 at -196 degrees C (and also with BET surface area), while diffusion into ultramicropores (<0.7 nm, determined by CO2-adsorption) is slow and presents minor influence on the total adsorption capacity. After saturation, thermal regeneration of spent adsorbents allows the removal of adsorbed products, enabling the reuse of samples whilst maintaining a significant performance.Portuguese Foundation for Science and Technology UIDB/00511/2020European Regional Development Funds (ERDF) through North Portugal Regional Operational Programme (NORTE 2020) NORTE-01-0247-FEDER-39789Project "HealthyWaters -Identification, Elimination, Social Awareness and Education of Water Chemical and Biological Micropollutants with Health and Environmental Implications" - NORTE 2020, under the PORTUGAL2020 Partnership Agreement NORTE-01-0145-FEDER-000069MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018-099224-B-I00Portuguese Foundation for Science and TechnologyEuropean Commission SFRH/BD/129235/2017National Fund through the Human Capital Operational Programme (POCH)European Social Fund through the Human Capital Operational Programme (POCH) MCIN/AEI RYC-2019-026634IEuropean Social Found (FSE) "El FSE invierte en tu futuro" RYC-2019-026634IUniversidad de Granada/CBU

Coupling Noble Metals and Carbon Supports in the Development of Combustion Catalysts for the Abatement of BTX Compounds in Air Streams

The catalytic combustion of volatile organic compounds (VOCs) is one of the most important techniques to remove these pollutants from the air stream, but it should be carried out at the lowest possible temperature, saving energy and avoiding the simultaneous formation of nitrogen oxides (NOx). Under these experimental conditions, the chemisorption of water generated from VOCs combustion may inhibit hydrophilic catalysts. Nowadays, a wide variety of carbon materials is available to be used in catalysis. The behavior of these hydrophobic materials in the development of highly active and selective combustion catalysts is analyzed in this manuscript. The support characteristics (porosity, hydrophobicity, structure, surface chemistry, etc.) and the active phase nature (noble metals: Pt, Pd) and dispersion were analyzed by several techniques and the results correlated with the dual adsorptive and/or catalytic performance of the corresponding catalysts. The coupling of highly active phases and carbon materials (activated carbons, honeycomb coated monoliths, carbon aerogels, etc.) with tuneable physicochemical properties leads to the complete abatement of benzene, toluene and xylenes (BTX) from dilute air streams, being selectively oxidized to CO2 at low temperatures

Wastewater Treatment by CatalyticWet Peroxidation Using Nano Gold-Based Catalysts: A Review

Nowadays, there is an increasing interest in the development of promising, e cient, and environmentally friendly wastewater treatment technologies. Among them are the advanced oxidation processes (AOPs), in particular, catalytic wet peroxidation (CWPO), assisted or not by radiation. One of the challenges for the industrial application of this process is the development of stable and e cient catalysts, without leaching of the metal to the aqueous phase during the treatment. Gold catalysts, in particular, have attracted much attention from researchers because they show these characteristics. Recently, numerous studies have been reported in the literature regarding the preparation of gold catalysts supported on various supports and testing their catalytic performance in the treatment of real wastewaters or model pollutants by CWPO. This review summarizes this research; the properties of such catalysts and their expected e ects on the overall e ciency of the CWPO process, together with a description of the e ect of operational variables (such as pH, temperature, oxidant concentration, catalyst, and gold content). In addition, an overview is given of the main technical issues of this process aiming at its industrial application, namely the possibility of using the catalyst in continuous flow reactors. Such considerations will provide useful information for a faster and more e ective analysis and optimization of the CWPO process.This work was financially supported by projects UID/EQU/00511/2019 - Laboratory for Process Engineering, Environment, Biotechnology and Energy - LEPABE – and by Associate Laboratory LSRE-LCM – UID/EQU/50020/2019 – funded by national (Portuguese) funds through FCT/MCTES (PIDDAC). SACC is thankful to FCT for Investigador FCT program (IF/01381/2013/CP1160/CT0007), with financing from the European Social Fund and the Human Potential Operational Program (POCH)

Metal-Carbon-CNF Composites Obtained by Catalytic Pyrolysis of Urban Plastic Residues as Electro-Catalysts for the Reduction of CO2

Metal–carbon–carbon nanofibers composites obtained by catalytic pyrolysis of urban plastic residues have been prepared using Fe, Co or Ni as pyrolitic catalysts. The composite materials have been fully characterized from a textural and chemical point of view. The proportion of carbon nanofibers and the final content of carbon phases depend on the used pyrolitic metal with Ni being the most active pyrolitic catalysts. The composites show the electro-catalyst activity in the CO2 reduction to hydrocarbons, favoring all the formation of C1 to C4 hydrocarbons. The tendency of this activity is in accordance with the apparent faradaic efficiencies and the linear sweep voltammetries. The cobalt-based composite shows high selectivity to C3 hydrocarbons within this group of compounds.This research is supported by the FEDER and Spanish projects CTQ2013-44789-R (MINECO) and P12-RNM-2892 (Junta de Andalucía). J.C.-Q. is grateful to the Junta de Andalucía for her research contract (P12-RNM-2892). A.E. acknowledges a predoctoral fellowship from Erasmus Mundus, Al-Idrissi, programme

Influence of Electrostatic Interactions During the Resorcinol-Formaldehyde Polymerization on the Characteristics of Mo-Doped Carbon Gels

The resorcinol (R)-formaldehyde (F) polymerization was carried out in different experimental conditions to obtain RF/Mo doped carbon xerogels with different morphology, porosity and nature and dispersion of metal. Attractive or repulsive electrostatic interactions were forced in the starting aqueous solution of RF-monomers using different synthesis conditions, namely, combinations of cationic or anionic surfactants, Mo-precursors and pH values. The results showed that when both cationic surfactant and Mo-precursor were used at neutral pH, attractive interactions with the anionic RF-macromolecules are favored during polymerization and the final carbon xerogel exhibited the most developed porosity and the strongest Mo-organic phase interaction, leading to deeper Mo-phase reduction during carbonization and the formation of highly-dispersed crystalline nanoparticles of Mo2C. On the contrary, the use of both anionic surfactant and Mo-precursor leads to repulsive interactions, which generates less porous carbon gels with a Mo-phase formed by large MoO3 platelet structures and low Mo-surface contents. RF/Mo-doped gels with intermediate properties were obtained by combining cationic and anionic surfactants, metal precursors or both. After carbonization, the obtained materials would be suitable to be used directly as catalysts with different physicochemical properties and active phases.Spanish Project from ERDF/Ministry of Science, Innovation and Universities-State Research Agency RTI2018-099224-B-I0

Functionalized Cellulose for the Controlled Synthesis of Novel Carbon–Ti Nanocomposites: Physicochemical and Photocatalytic Properties

H.H. gratefully thanks a predoctoral fellowship from Erasmus Mundus (Al-Idrisi II). E.B.-G. is grateful to MINECO for her postdoctoral fellowship (FJCI-2015-23769). S.M.-T. acknowledges the financial support from the University of Granada (Reincorporación Plan Propio). “Unidad de Excelencia Química Aplicada a Biomedicina y Medioambiente” of the University of Granada (UEQ - UGR) is gratefully acknowledged for the technical assistance.Carbon–Ti nanocomposites were prepared by a controlled two-step method using microcrystalline cellulose as a raw material. The synthesis procedure involves the solubilization of cellulose by an acid treatment (H3PO4 or HNO3) and the impregnation with the Ti precursor followed of a carbonization step at 500 or 800 ◦C. The type of acid treatment leads to a different functionalization of cellulose with phosphorus- or oxygen-containing surface groups, which are able to control the load, dispersion and crystalline phase of Ti during the composite preparation. Thus, phosphorus functionalities lead to amorphous carbon–Ti composites at 500 ◦C, while TiP2O7 crystals are formed when prepared at 800 ◦C. On the contrary, oxygenated groups induce the formation of TiO2 rutile at an unusually low temperature (500 ◦C), while an increase of carbonization temperature promotes a progressive crystal growth. The removal of Orange G (OG) azo dye in aqueous solution, as target pollutant, was used to determine the adsorptive and photocatalytic efficiencies, with all composites being more active than the benchmark TiO2 material (Degussa P25). Carbon–Ti nanocomposites with a developed micro-mesoporosity, reduced band gap and TiO2 rutile phase were the most active in the photodegradation of OG under ultraviolet irradiation.This work was financially supported by the Spanish Projects ref. RTI2018-099224-B-I00 from ERDF/Ministry of Science, Innovation and Universities—State Research Agency and Junta de Andalucía - Grant ref. RMN-172

Functionalized Graphene Derivatives and TiO2 for High Visible Light Photodegradation of Azo Dyes

Functionalized graphene derivatives including graphene oxide (GO), reduced graphene oxide (rGO), and heteroatom (nitrogen/sulphur (N/S) or boron (B))-doped graphene were used to synthesize composites with TiO2 (T). The photocatalytic performance of composites was assessed for the degradation of Orange G dye (OG) under simulated solar light. All the prepared graphene derivatives—TiO2 composites showed better photocatalytic performance than bare TiO2. A higher photocatalytic activity was found for the composites containing GO and N/S co-doped rGO (kapp = 109.2 × 10−3 and 48.4 × 10−3 min−1 , for GO-T and rGONS-T, respectively). The influence of both initial solution pH and the reactive species involved in the OG degradation pathway were studied. The photocatalytic activity of the samples decreased with the increase of the initial pH (from 3.0 to 10.0) due to the occurrence of electrostatic repulsive forces between the photocatalysts surface and the molecules of OG, both negatively charged. The use of selective scavengers showed that although the photogenerated holes dominate the degradation mechanism, radicals and singlet oxygen also participate in the OG degradation pathway. In addition, reutilization experiments indicated that the samples were stable under the reaction conditions used.ERDF/Ministry of Science, Innovation and Universities-State Research Agency RTI2018-099224-B-I0

Photodegradation of cytostatic drugs by g-C3N4: Synthesis, properties and performance fitted by selecting the appropriate precursor

Graphitic carbon nitride (g-C3N4) was synthetized by a one-step thermal method from different N-rich precursors, namely melamine, dicyandiamide, urea, thiourea and cyanamide. The structure, optical and physicochemical properties of g-C3N4 materials were studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, among others. Both melamine and dicyandiamide provided a less porous structure composed by large flake sheets, whereas urea and thiourea favoured g-C3N4 composed by small flat sheets and wrinkles with a larger porosity. The establishment of more condensed g-C3N4 networks with a reduced band gap was also evidenced for melamine and dicyandiamide precursors, while urea favoured less condensed melem or melon structures. The photoactivity of the different g-C3N4 was assessed for the removal of an aqueous solution containing 5-fluorouracil (5-FU), cyclophosphamide (CP) or a mixture of both cytostatic drugs, under near UV-Vis and solar-LED irradiations. The best performing photocatalysts under near UV-Vis irradiation, were those prepared from melamine (kapp = 14.6 × 10–2 min–1 for 5-FU) and thiourea (kapp = 2.5 × 10–2 min–1 for CP), while urea was the most active under solar-LED irradiation (kapp = 0.183 × 10–2 min–1 for 5-FU). In addition, CP was more resistant to be degraded than 5-FU, and a competitive effect for the generated hydroxyl radicals was evidenced when both pollutant molecules were in the same solution. The photoactivity of g-C3N4 materials was justified by the combination of various effects: (i) surface area, (ii) well-connected and condensed g-C3N4 structures and (iii) high surface C/N ratios with nitrogen vacanciesSpanish Projects from MCIN/AEI/FEDER "Una manera de hacer Europa" RTI2018-099224-B-I00FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades B-RNM-486-UGR20Junta de Andalucia-Consejeria de Universidad, Investigacion e Innovacion -Proyecto P21_00208MICIN/AEIEuropean Social Found (FSE) PRE2019-087946MICIN/AEI RYC-2019-026634-IFSE "El FSE invierte en tu futuro"Universidad de Granada/CBU