Publications by authors named "Kaouther Zaafouri"

6 Publications

  • Page 1 of 1

Municipal sewage sludge energetic conversion as a tool for environmental sustainability: production of innovative biofuels and biochar.

Environ Sci Pollut Res Int 2021 Feb 6;28(8):9777-9791. Epub 2020 Nov 6.

Laboratory of Wind Energy Management and Waste Energy Recovery (LMEEVED), Research and Technology Center of Energy (CRTEn), B.P. 95, 2050, Hammam-Lif, Tunisia.

In this study, municipal sewage sludge (MSS) is converted simultaneously into renewable biofuels (bio-oil, syngas) and high value-added products (biochar) using a fixed bed pyrolyzer. This work examines the combined effect of two factors: final pyrolysis temperature (°C) and MSS moisture content (%) on pyrogenic product yields and characteristics. A centered composite experimental design (CCD) is established for pyrolysis process optimization by adopting the response surface methodology (RSM). The statistical results indicate that the optimal conditions considering all studied factors and responses are 550 °C as final pyrolysis temperature and 15% as MSS moisture content. In these optimal conditions, biofuels yield is around 48 wt%, whereas biochar yield is about 52 wt%. The pyrolysis products characterizations reveal that (i) pyrolytic oil has a complex molecular composition rich with n-alkanes, n-alkenes, carboxylic acids, and aromatic compounds; (ii) bio-oil presents a high-energy content (high heating value HHV around 30.6 MJ/kg); (iii) syngas mixture has a good calorific value (HHV up to 8 MJ/kg), which could be used as renewable energy vector or for pyrolysis reactor heating; and (iv) biochar residue has good aliphatic and oxygenated group contents favoring its application as biofertilizer. These findings suggest that MSS conversion into biofuels and biochar is an appropriate approach for MSS treatment. MSS-to-energy could be proposed as an element for circular economy concept due to its effectiveness in producing high value-added and sustainable products and reducing environmental problems linked to MSS disposal.
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http://dx.doi.org/10.1007/s11356-020-11400-zDOI Listing
February 2021

Evaluation of the Efficiency of Ethanol Precipitation and Ultrafiltration on the Purification and Characteristics of Exopolysaccharides Produced by Three Lactic Acid Bacteria.

Biomed Res Int 2018 18;2018:1896240. Epub 2018 Sep 18.

National Research Center for Materials Science, Borj-Cedria Technopark, BP N°73, 8027 Soliman, Tunisia.

Exopolysaccharides (EPS) produced by three Lactic Acid Bacteria strains, SLT10, C7, and B3, were isolated using two methods: ethanol precipitation (EPS-ETOH) and ultrafiltration (EPS-UF) through a 10 KDa cut-off membrane. EPS recovery by ultrafiltration was higher than ethanol precipitation for SLT10 and C7. However, it was similar with both methods for B3. The monomer composition of the EPS fractions revealed differences in structures and molar ratios between the two studied methods. EPS isolated from SLT10 are composed of glucose and mannose for EPS-ETOH against glucose, mannose, and rhamnose for EPS-UF. EPS extracted from C7 and B3 showed similar composition (glucose and mannose) but different molar ratios. The molecular weights of the different EPS fractions ranged from 11.6±1.83 to 62.4±2.94 kDa. Molecular weights of EPS-ETOH fractions were higher than those of EPS-UF fractions. Fourier transform infrared (FTIR) analysis revealed a similarity in the distribution of the functional groups (O-H, C-H, C=O, -COO, and C-O-C) between the EPS isolated from the three strains.
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http://dx.doi.org/10.1155/2018/1896240DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6167595PMC
January 2019

Pyrolysis of Date palm waste in a fixed-bed reactor: Characterization of pyrolytic products.

Bioresour Technol 2018 Jan 11;247:363-369. Epub 2017 Sep 11.

Laboratory of Wastewater Treatment and Recycling, Research and Technology Center of Water, BP 273, 8020 Soliman, Tunisia.

The pyrolysis of several Tunisian Date Palm Wastes (DPW): Date Palm Rachis (DPR), Date Palm Leaflets (DPL), Empty Fruit Bunches (EFB) and Date Palm Glaich (DPG) was run using a fixed-bed reactor, from room temperature to 500°C, with 15°C/min as heating rate and -5°C as condensation temperature, in order to produce bio-oil, biochar and syngas. In these conditions, the bio-oil yield ranges from 17.03wt% for DPL to 25.99wt% for EFB. For the biochar, the highest yield (36.66wt%) was obtained for DPL and the lowest one (31.66wt%) was obtained from DPG while the syngas production varies from 39.10wt% for DPR to 46.31wt% DPL. The raw material and pyrolysis products have been characterized using elemental analysis thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). The syngas composition has been characterized using gas analyzer.
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http://dx.doi.org/10.1016/j.biortech.2017.09.066DOI Listing
January 2018

Hydrogen-Rich Syngas Production from Gasification and Pyrolysis of Solar Dried Sewage Sludge: Experimental and Modeling Investigations.

Biomed Res Int 2017 9;2017:7831470. Epub 2017 Aug 9.

Department of Geology, Faculty of Sciences of Tunis, University of Tunis El Manar, Tunis, Tunisia.

Solar dried sewage sludge (SS) conversion by pyrolysis and gasification processes has been performed, separately, using two laboratory-scale reactors, a fixed-bed pyrolyzer and a downdraft gasifier, to produce mainly hydrogen-rich syngas. Prior to SS conversion, solar drying has been conducted in order to reduce moisture content (up to 10%). SS characterization reveals that these biosolids could be appropriate materials for gaseous products production. The released gases from SS pyrolysis and gasification present relatively high heating values (up to 9.96 MJ/kg for pyrolysis and 8.02  9.96 MJ/kg for gasification) due to their high contents of H (up to 11 and 7 wt%, resp.) and CH (up to 17 and 5 wt%, resp.). The yields of combustible gases (H and CH) show further increase with pyrolysis. Stoichiometric models of both pyrolysis and gasification reactions were determined based on the global biomass formula, CHONS, in order to assist in the products yields optimization.
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http://dx.doi.org/10.1155/2017/7831470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5569640PMC
July 2018

Optimization of Hydrothermal and Diluted Acid Pretreatments of Tunisian (L.) Fibers for 2G Bioethanol Production through the Cubic Central Composite Experimental Design CCD: Response Surface Methodology.

Biomed Res Int 2017 24;2017:9524521. Epub 2017 Jan 24.

Laboratory of Microbial Ecology and Technology (LETMi), The National Institute of Applied Sciences and Technology (INSAT), Carthage University, 2 Boulevard de la Terre, BP 676, 1080 Tunis, Tunisia.

This paper opens up a new issue dealing with (LC) lignocellulosic biomass recovery in order to produce 2G bioethanol. LC fibers are composed of three principal fractions, namely, -cellulose (45.80%  ± 1.3), hemicelluloses (20.76%  ± 0.3), and lignins (13.15%  ± 0.6). The optimization of LC fibers hydrothermal and diluted acid pretreatments duration and temperature were achieved through the cubic central composite experimental design CCD. The pretreatments optimization was monitored via the determination of reducing sugars. Then, the 2G bioethanol process feasibility was tested by means of three successive steps, namely, LC fibers hydrothermal pretreatment performed at 96°C during 54 minutes, enzymatic saccharification carried out by means of a commercial enzyme AP2, and the alcoholic fermentation fulfilled with . LC fibers hydrothermal pretreatment liberated 33.55 g/kg of reducing sugars. Enzymatic hydrolysis allowed achieving 59.4 g/kg of reducing sugars. The conversion yield of reducing sugar to ethanol was 88.66%. After the distillation step, concentration of ethanol was 1.58% with a volumetric yield about 70%.
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http://dx.doi.org/10.1155/2017/9524521DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5294667PMC
March 2017

Enhancement of biofuels production by means of co-pyrolysis of Posidonia oceanica (L.) and frying oil wastes: Experimental study and process modeling.

Bioresour Technol 2016 May 15;207:387-98. Epub 2016 Feb 15.

Laboratory of Microbial Ecology and Technology, LETMi-INSAT, The National Institute of Applied Sciences and Technology INSAT, Carthage University, 2 Boulevard de la Terre, B.P 676, 1080 Tunis, Tunisia.

Energy recovery from lignocellulosic solid marine wastes, Posidonia oceanica wastes (POW) with slow pyrolysis responds to the growing trend of alternative energies as well as waste management. Physicochemical, thermogravimetric (TG/DTG) and spectroscopic (FTIR) characterizations of POW were performed. POW were first converted by pyrolysis at different temperatures (450°C, 500°C, 550°C and 600°C) using a fixed-bed reactor. The obtained products (bio-oil, syngas and bio char) were analyzed. Since the bio-oil yield obtained from POW pyrolysis is low (2wt.%), waste frying oil (WFO) was added as a co-substrate in order to improve of biofuels production. The co-pyrolysis gave a better yield of liquid organic fraction (37wt.%) as well as syngas (CH4,H2…) with a calorific value around 20MJ/kg. The stoichiometric models of both pyrolysis and co-pyrolysis reactions were performed according to the biomass formula: CαHβOγNδSε. The thermal kinetic decomposition of solids was validated through linearized Arrhenius model.
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http://dx.doi.org/10.1016/j.biortech.2016.02.004DOI Listing
May 2016
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