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•Many evidences are showed about favorable uses of zeolite in biological processes.•In aerobic processes zeolite is used as ion-exchanger and biomass carrier.•In anaerobic digestion, ...zeolite is used to remove ammonia and biomass carrier.•In composting, zeolite is used to retain ammonia and to remove heavy metals.•Zeolite has been used at industrial scale mainly in nitrogen removal.
This review reports the use of zeolites in biological processes such as anaerobic digestion, nitrification, denitrification and composting, review that has not been proposed yet. It was found that aerobic processes (activated sludge, nitrification, Anammox) use zeolites as ion-exchanger and biomass carriers in order to improve the seattlebility, the biomass growth on zeolite surface and the phosphorous removal. In the case of anaerobic digestion and composting, zeolites are mainly used with the aim of retaining inhibitors such as ammonia and heavy metals through ion-exchange. The inclusion of zeolite effect on mathematical models applied in biological processes is still an area that should be improved, including also the life cycle analysis of the processes that include zeolites. At the same time, the application of zeolites at industrial or full-scale is still very scarce in anaerobic digestion, being more common in nitrogen removal processes.
Anaerobic digestion is considered a competitive source for the production of renewable energy as far as efficiency and cost are concerned. To evaluate the anaerobic biodegradability of an organic ...substrate such as feedstocks, a test known as biochemical methane potential (BMP) has been commonly used. Current worldwide interest in using different organic substrates for anaerobic bioconversion is growing but there is a lack of clear references and comparability as a result of multiple factors that affect BMP determination. Several batch methods have been used to determine the methane potential. However, these technical approaches vary significantly from one reported method to the next another. In this review, the research works on the influence of different parameters of BMP determination have been discussed for critical and comparative evaluation. In addition, the extensive literature previously published dealing with BMP assays has been compiled and summarized focusing on two main subjects: firstly, methane yields of substrates, and secondly, the description of the various experimental procedures used to achieve the reported data.
New results about the tribocorrosion resistance and cytotoxicity of FeB-Fe2B layer developed by the powder-pack boriding process on the surface of AISI 316 L steel are presented in this work. ...Initially, the tribocorrosion tests in the borided AISI 316 L steel and the untreated material (AISI 316 L steel) were performed in Hank's solution, using a ball-on-flat configuration, which was connected with a three electrode-chemical cell. The sliding tests, in the presence or absence of corrosion, were performed under 20N normal force using an alumina ball as a counter body. For the overall experimental conditions, the material loss for each material was estimated according to the ASTM G119 procedure. Further, the in vitro cytocompatibility of FeB-Fe2B layer on AISI 316 L steel and the untreated material was evaluated by the indirect contact method, in which cell lines of immortalized human fibroblast (CHON-002) and normal renal epithelium of Cercopithecus aethiops (Vero) were used.
The results showed that the presence of FeB-Fe2B layer on the AISI 316 L steel improves the tribocorrosion resistance 1.5 times than that of the untreated material, with a presence of a wear-corrosion degradation mechanism in contrast with a wear-dominated regime for the untreated material. Finally, the cytotoxicity tests revealed satisfactory properties in terms of effects on survival and proliferative activity of human fibroblasts and Vero cells on the surface of the borided AISI 316 L steel.
•New results about the tribocorrosion resistance of FeB-Fe2B layer were obtained.•A wear corrosion dominated-regime was estimated for the borided AISI 316 L steel.•Contribution of synergy to the total material loss was reduced by the boride layer.•The FeB-Fe2B layer revealed good cytocompatibility with Vero and CHON-002 cells.
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•Effect of different fly ash particle sizes on anaerobic digestion was studied.•Particle sizes between 0.8 and 2.36mm were evaluated in mesophilic conditions.•Particle sizes in the ...range of 1–1.4mm enhanced methane yield and biodegradability.•Metal concentrations in sludge digestate allow its use in agricultural soils.
The influence of fly ash particle size on methane production and anaerobic biodegradability was evaluated. Assays with different fly ash particle sizes (0.8–2.36mm) at a concentration of 50mg/L were ran under mesophilic conditions. In anaerobic processes operating with fly ash, greater removal of both volatile total and suspended solids, chemical oxygen demand (total and soluble) was achieved, with an increase of methane production between 28% and 96% compared to the control reactors. The highest increase occurred at ash particles sizes of 1.0–1.4mm. The metal concentrations in the digestates obtained after anaerobic digestion of sewage sludge are far below those considered as limiting for the use of sludge in soils.
Olive mill solid waste (OMSW) is a pollutant waste coming from olive oil elaboration by the two-phase centrifugation system. OMSW has a high organic matter content and unbalanced carbon to nitrogen ...(C/N) ratio, 31/1, which avoids obtaining high methane yields in the anaerobic digestion of this waste. In the present study a microalgae, Dunaliella salina, was employed as co-substrate for the OMSW anaerobic digestion in order to decrease the C/N ratio and increase its biodegradability. Different co-digestion mixtures (C/N ratios) were studied. The increase of D. salina from 25% to 50% in the co-digestion mixture clearly increased the biodegradability of the sole substrates. The highest biodegradability was found for the co-digestion mixture 50% OMSW-50% D. salina. Nevertheless, the maximum methane production, 330mLCH4/gVSadded, and the highest methane production rate were obtained for the co-digestion mixture 75% OMSW-25% D. salina, keeping a C/N ratio near to 26.7/1.
•Volume and shear damage measures have been incorporated into a hyper-elastoplastic framework to model inelastic rock deformation.•A novel feature of the formulation is a thermodynamically consistent ...finite deformation framework that makes connections between inelastic volume change and damage.•A unique feature of the formulation is the ability of the model to capture hardening/softening responses entirely through damage and damage-effective stresses, and not from the more commonly employed phenomenological approach.•The model was used to simulate the inelastic deformation response of limestone subjected to a variety of stress paths.•Stress-point and boundary-value problem simulations were conducted to test the robustness of the formulation.
Relations between porosity, damage, and bulk plasticity are examined in the context of continuum damage and hyper-elastoplasticity of porous rocks. Attention is given to a thermodynamically consistent derivation of the damage evolution equations and their role in the constitutive equations, for which the Eshelby stress is found to be important. The provided phenomenological framework allows for volumetric damage associated with pore growth to be distinguished from the isochoric damage associated with distributed microcracks, and a novel Drucker-Prager/cap type material model that includes damage evolution is presented. The model is shown to capture well the hardening/softening behavior and pressure dependence of the so-called brittle-ductile transition by comparison with confined triaxial compression measurements from the literature. Non-linear finite element simulations are also provided of the prediction of damage within porous limestone around a horizontal borehole wall.
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•Homogenization of the OFMSW after its grinding and sieving increased methane yield.•Maximum methane production rate increased by 2.4 times for pretreated OFMSW.•Co-digestion of LFHTC ...with OFMSW is a promising option to manage this waste.•The methane yield of anaerobic co-digestion with 25%LFHTC is similar to that observed for OFMSW.
In the present study, the influence of substrate pre-treatment (grinding and sieving) on batch anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) was first assessed, then followed by co-digestion experiments with the liquid fraction from hydrothermal carbonization (LFHTC) of dewatered sewage sludge (DSS). The methane yield of batch anaerobic digestion after grinding and sieving (20 mm diameter) the OFMSW was considerably higher (453 mL CH4 STP g−1 VSadded) than that of untreated OFMSW (285 mL CH4 STP g−1 VSadded). The modified Gompertz model adequately predicted process performance. The maximum methane production rate, Rm, for ground and sieved OFMSW was 2.4 times higher than that of untreated OFMSW. The anaerobic co-digestion of different mixtures of OFMSW and LFHTC of DSS did not increase the methane yield above that of the anaerobic digestion of OFMSW alone, and no synergistic effects were observed. However, the co-digestion of both wastes at a ratio of 75% OFMSW-25% LFHTC provides a practical waste management option. The experimental results were adequately fitted to a first-order kinetic model showing a kinetic constant virtually independent of the percentage of LFHTC (0.52–0.56 d−1) and decreasing slightly for 100% LFHTC (0.44 d−1).
The adsorption of methylene blue (MB) on three commercial granular activated carbons (GACs), 12
×
40 mesh size, namely Filtrasorb 400, Norit and Picacarb has been researched. A comparative study of ...adsorptive capacity using the proposed single-point test and the traditional multi-point isotherm test was carried out. For the single-point test, the influence of some parameters such as MB/GACs mass ratio and contact time were evaluated. For this test the adsorptive capacities of the three GACs studied were 319
±
14, 280
±
7 and 260
±
6
mg
g
−1 for Filtrasorb 400, Norit and Picacarb, respectively. For multi-point isotherm adsorption test the Langmuir model was used. The parameters involved were obtained by linear and non-linear regression methods. The maximum adsorptive capacity values obtained for both methods were similar and statistically not different than those obtained with the single-point tests. This experimental work also aimed at establishing a relationship between the adsorbent particle size and the adsorptive capacity which could be used complementarily to evaluate the quality of GACs as adsorbents. For a mean particle diameter of 1
mm and after 24
h of contact time the adsorptive capacity values were 255
±
7, 222
±
7 and 160
±
7
mg
g
−1 for Filtrasorb 400, Norit and Picacarb, respectively.
This study evaluated the influence of the TiO2 nanoparticles (NPs) on the mechanical and chemical performance of Sn and Sn–Ag alloys. The XRD (X-ray diffraction) and HR-TEM (high ...resolution-transmission electron microscopy) methods were used to characterize the NPs synthesized by the sol-gel microwave process. The chemical composition of the alloys was Sn, Sn+3TiO2 NPs, Sn–5Ag+1.5TiO2 NPs, Sn–10Ag, and Sn–10Ag+3TiO2 NPs, obtained from an experimental factorial design (EFD). A statistical model was used to determine the mechanical and chemical properties, showing the Vickers hardness response surface, tensile strength, wear, and corrosion resistance. The wear and corrosion tests for the various alloy compositions were performed using human artificial saliva solution. The results indicated that the Sn–10Ag+3TiO2 NPs exhibited the highest mechanical performance due to their increased hardness (380 HV), tensile strength (370 N), and wear resistance (0.34 × 10−3 mm3 Nm−1); in all the cases, the inclusion of TiO2 NPs enhanced the corrosion resistance of the alloys. According to the American Dental Association (ADA), Sn–10Ag+3TiO2 NPs alloy could be classified as a possible type IV restorative material.
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•The sol-gel microwave method was successfully used for the synthesis of TiO2 NPs.•The addition of TiO2 NPs modified the microstructure Sn–Ag alloys.•The addition of TiO2 NPs enhanced hardness and wear performance of the Sn–Ag alloy.•The TiO2 NPs remarkably increased the corrosion resistance of Sn–Ag alloy.•According to the results, Sn–Ag + NPs might be reclassified as ADA type IV material.
Completely mixed batch reactors were used to compare the methane production from maize at inoculum to substrate volatile solids ratios (
r
I/S) of 3, 2, 1.5 and 1. The tests were carried out at 35
°C ...and run against a control of inoculum without substrate. The stability and progress of the reaction from solid substrate to gaseous end product was monitored by measuring the pH, soluble chemical oxygen demand (CODs), total alkalinity (TA), volatile fatty acids (VFA) and gas composition on a daily basis. The results showed that the yield coefficient showed little variation over the range used, with an average value of 211
±
6
ml CH
4 at standard temperature and pressure (STP) conditions g
V
S
added
−
1
. The methane production curves were further analysed to give values for the maximum specific methane production rate, ranging from 10
ml CH
4 g
VSS
−1
day
−1 for a
r
I/S of 3–23
ml CH
4 g
VSS
−1
day
−1 for a
r
I/S of 1. The initial buffering capacity of the system was enhanced by addition of NaHCO
3 to 9100
mg CaCO
3 l
−1 which allowed digestion to proceed within the pH range 7.2–8.0 and at TVFA to TA ratio below the critical limit of 0.4. The largest proportion of the CODs was in the form of VFA and the reactor with the highest VS loading showed an accumulation of longer chain acids.
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