Cheese whey management by catalytic steam reforming and aqueous phase reforming

Cheese whey is a yellowish liquid by-product of the cheese making process. Owing to its high BOD and COD values, this feedstock should not be directly discharged into the environment without appropriate treatment. The management of this wastewater has become an important issue, and new treatments must be sought. This work addresses the valorisation of cheese whey by steam reforming and aqueous phase reforming. The catalytic steam reforming of cheese whey turned out to be a promising valorisation route for H2 production from this effluent. This process enabled the organic compounds present in the cheese whey to be transformed into a rich H2 gas (35% of the C of the feed was transformed into a gas with 70 vol.% of H2). This significantly reduced the amount of carbon present in the original feedstock, producing an almost carbon-free liquid stream. The aqueous phase reforming of cheese whey allowed 35% of the carbon present in the whey to be transformed into gases and 45% into valuable liquids. The gas was principally made up of H2 and CO2, while a mixture of added-value liquids such as aldehydes, carboxylic acids, alcohols and ketones constituted the liquid phase. However, both valorisation routes produced a substantial amount of solid. The formation of this solid was promoted by the presence of salts in the original feedstock and caused operational problems for both valorisation processes. In addition, it hampered gas production in the case of steam reforming and reduced gas and liquid formation when using aqueous phase reforming as the valorisation route. The filtration of cheese whey slightly decreased the solid formation in both processes due to the reduction of proteins and fats, both of which partly contribute to such formation. Less solid was formed in the experiments conducted with lactose than in those conducted with whole and with filtered cheese whey

Hydrogen production from cheese whey by catalytic steam reforming: Preliminary study using lactose as a model compound

Cheese whey is a yellowish liquid by-product of the cheese making process. Owing to its high BOD and COD values, this feedstock should not be directly discharged into the environment without appropriate treatment. Before dealing with real cheese whey, this work addresses the production of a rich hydrogen gas from lactose (the largest organic constituent of this waste) by catalytic steam reforming. This reforming process has been theoretically and experimentally studied. The theoretical study examines the effect of the temperature (300-600 °C), lactose concentration (1-10 wt.%) and N2 (0-80 cm3 STP/min) and liquid flow (0.1-0.5 mL/min) rates on the thermodynamic composition of the gas. The results show that the temperature and lactose concentration exerted the greatest influence on the thermodynamics. The experimental study, conducted in a fixed bed reactor using a Ni-based catalyst, considers the effect of the temperature (300-600 °C), lactose concentration (1-10 wt.%) and spatial time (4-16 g catalyst min/g lactose) on the global lactose conversion, product distribution on a carbon basis (gas, liquid and solid) and the compositions of the gas and liquid phases. Complete lactose conversion was achieved under all the experimental conditions. The carbon converted into gas, liquid and solid was 2-97%, 0-66% and 0-94%, respectively. The gas phase was made up of a mixture of H2 (0-70 vol.%), CO2 (20-70 vol.%), CO (2-34 vol.%) and CH4 (0-3 vol.%). The liquid phase consisted of a mixture of aldehydes, ketones, carboxylic acids, sugars, furans, alcohols and phenols. Optimal conditions for cheese whey valorisation were sought considering the energetic aspects of the process. Using a lactose concentration similar to that of cheese whey (5.5 wt.%), maxima for the CC gas (88%) and the proportion of H2 (67 vol.%) in the gas together with a carbon-free liquid stream can be achieved at 586 °C using a spatial time of 16 g catalyst min/g lactose. Theoretically, the combustion of 20% of this gas provides the energy necessary for the process enabling the transformation of 68% of the carbon present in the initial effluent into a H2 rich gas (67 vol.%) with a global H2 yield of 16 mol H2/mol lactose. In a real case it would be necessary to increase the amount of gas combusted to compensate for heat losses

Influence of Bi and Mn on the green luminescence of ZnO ceramics

The effect of the addition of Bi and Mn on the photoluminescence from ZnO ceramics has been investigated. The effect of the presence of impurities on the green luminescence band can be compared to the effect of oxidizing treatments. A narrow green band has been observed in Mn‐doped samples

Effect of biodiesel-derived impurities (acetic acid, methanol and potassium hydroxide) on the aqueous phase reforming of glycerol

This work analyses the influence of three biodiesel-derived impurities (CH3OH, CH3COOH and KOH) on the aqueous phase reforming of glycerol at 220 °C and 44 bar using a Ni-La/Al2O3 catalyst. The experiments were planed according to a factorial 2k design and analysed by means of an analysis of variance (ANOVA) test to identify the effect of each impurity and all possible binary and ternary combinations. The presence of CH3OH decreased the glycerol conversion, while CH3COOH and KOH decreased and increased the gas production, respectively. Catalyst deactivation took place under acidic conditions due to the loss of part of the active phase of the catalyst through leaching. The gas phase was made up of H2, CO2, CO and CH4. KOH exerted the greatest influence on the gas composition, increasing H2 production due to the greater gas production and the lower H2 consumption in the hydrogenation reactions. The liquid phase was made up of aldehydes, monohydric and polyhydric alcohols, C3 and C4 ketones and esters. CH3OH increased the proportion of monohydric alcohols, while CH3COOH promoted dehydration reactions, leading to an increase in the relative amount of C3-ketones

Optical quality variation of different intraocular lens designs in a model eye: lens placed correctly and in an upside-down position

Introduction: Intraocular lenses (IOLs) may lose their optical quality if they are not correctly placed inside the capsular bag once implanted. One possible malpositioning of the IOL could be the implantation in an upside-down position. In this work, three aspheric IOLs with different spherical aberration (SA) have been designed and numerically tested to analyse the optical quality variation with the IOL flip, and misalignments, using a theoretical model eye. Methods: Using the commercial optical design software OSLO, the effect of decentration and tilt was evaluated by numerical ray tracing in two conditions: IOL in their designed position and flipped. The Atchison theoretical model eye used. Seven IOL designs of +27.00 diopters were used: a lens with negative SA to correct the corneal SA, a lens to partially correct the corneal SA and a lens to not add any SA to the cornea (aberration-free IOL). These lenses were designed with the aspherical surface located on the anterior and posterior IOL surface. A lens with no aspherical surfaces was also included. For the optical quality analysis, the Modulation Transfer Function (MTF) and Zernike wavefront aberration coefficients of defocus, astigmatism and primary coma were used. Results: Off-centering and tilting the IOL reduced overall MTF values, and increased wavefront aberration errors. With the IOL correctly positioned within the capsular bag, an aberration-free IOL is the best choice for maintaining optical quality. When the IOL is flipped inside the capsular bag the optical quality changes, with the aberration-free IOL and the IOL without aspheric surfaces providing the worst results. With the lens in an upside-down position, an IOL design to partially correct corneal SA shows the best optical quality results in decentration and tilt. Conclusion: The aberration-free IOL is the best choice when minimal postoperative errors of decentration or tilt are predicted. With IOL flip, the negative SA lens design is the best choice, regarding the root mean square wavefront aberrations. However, in a proper IOL implantation, the IOL designed to partially compensate the corneal SA including asphericity on its posterior surface is the better possible option, even in the presence of decentration or tilt

Analysis and optimisation of H2 production from crude glycerol by steam reforming using a novel two step process

This work studies the valorisation of biodiesel-derived glycerol to produce a hydrogen rich gas by means of a two-step sequential process. Firstly, the crude glycerol was purified with acetic acid to reduce problematical impurities. The effect of the final pH (5-7) on the neutralisation process was addressed and it was found that a pH of 6 provided the best phase separation and the greatest glycerol purity. Secondly, the refined glycerol was upgraded by catalytic steam reforming and this step was theoretically and experimentally studied. The theoretical study analyses the effect of the temperature (400-700°C), glycerol concentration (10-50 wt.%) and N2 (225-1347 cm3 STP/min) and liquid flow (0.5-1 mL/min) rates on the thermodynamic composition of the gas. The results show that the temperature and glycerol concentration exerted the greatest influence on the thermodynamics. The experimental study considers the effect of the temperature (400-700°C), glycerol concentration (10-50 wt.%) and spatial time (3-17 g catalyst min/g glycerol) on the product distribution in carbon basis (gas, liquid and solid) and on the composition of the gas and liquid phases. The experiments were planned according to a 2 level 3 factor Box-Wilson Central Composite Face Centred (CCF, a: ± 1) design, which is suitable for studying the influence of each variable as well as all the possible interactions between variables. The results were analysed with an analysis of variance (ANOVA) with 95% confidence, enabling the optimisation of the process. The gas phase was made up of a mixture of H2 (65-95 vol.%), CO2 (2-29 vol.%), CO (0-18 vol.%) and CH4 (0-5 vol.%). Temperatures of 550°C and above enabled thermodynamic compositions for the gas to be achieved and helped diminish carbon formation. A possible optimum for H2 production was found at a temperature of around 680°C, feeding a glycerol solution of 37 wt.% and using a spatial time of 3 g catalyst min/g glycerol. These conditions provide a 95% carbon conversion to gas, having the following composition: 67 vol.% H2, 22 vol.% CO2, 11 vol.% CO and 1 vol.% CH4

On the Relationship between Corneal Biomechanics, Macrostructure, and Optical Properties

Optical properties of the cornea are responsible for correct vision; the ultrastructure allows optical transparency, and the biomechanical properties govern the shape, elasticity, or stiffness of the cornea, affecting ocular integrity and intraocular pressure. Therefore, the optical aberrations, corneal transparency, structure, and biomechanics play a fundamental role in the optical quality of human vision, ocular health, and refractive surgery outcomes. However, the inter-relationships of those properties are not yet reported at a macroscopic scale within the hierarchical structure of the cornea. This work explores the relationships between the biomechanics, structure, and optical properties (corneal aberrations and optical density) at a macro-structural level of the cornea through dual Placido-Scheimpflug imaging and air-puff tonometry systems in a healthy young adult population. Results showed correlation between optical transparency, corneal macrostructure, and biomechanics, whereas corneal aberrations and in particular spherical terms remained independent. A compensation mechanism for the spherical aberration is proposed through corneal shape and biomechanics

In vivo biomechanical response of the human cornea to acoustic waves

The cornea is the optical window to the brain. Its optical and structural properties are responsible for optical transparency and vision. The shape, elasticity, rigidity, or stiffness are due to its biomechanical properties, whose stability results in ocular integrity and intraocular pressure dynamics. Here, we report in vivo observations of shape changes and biomechanical alterations in the human cornea induced by acoustic wave pressure within the frequency range of 50–350 Hz and the sound pressure level of 90 dB. The central corneal thickness (CCT) and eccentricity (e2) were measured using Scheimpflug imaging and biomechanical properties [corneal hysteresis (CH) and intraocular pressure (IOP)] were assessed with air-puff tonometry in six young, healthy volunteers. At the specific 150 Hz acoustic frequency, the variations in e2 and CCT were 0.058 and 7.33 µm, respectively. Biomechanical alterations were also observed in both the IOP (a decrease of 3.60 mmHg) and CH (an increase of 0.40 mmHg)

Cheese whey valorisation: Production of valuable gaseous and liquid chemicals from lactose by aqueous phase reforming

Cheese effluent management has become an important issue owing to its high biochemical oxygen demand and chemical oxygen demand values. Given this scenario, this work addresses the valorisation of lactose (the largest organic constituent of this waste) by aqueous phase reforming, analysing the influence of the most important operating variables (temperature, pressure, lactose concentration and mass of catalyst/lactose mass flow rate ratio) as well as optimising the process for the production of either gaseous or liquid value-added chemicals. The carbon converted into gas, liquid and solid products varied as follows: 5–41%, 33–97% and 0–59%, respectively. The gas phase was made up of a mixture of H2 (8–58 vol.%), CO2 (33–85 vol.%), CO (0–15 vol.%) and CH4 (0–14 vol.%). The liquid phase consisted of a mixture of aldehydes: 0–11%, carboxylic acids: 0–22%, monohydric alcohols: 0–23%, polyhydric-alcohols: 0–48%, C3-ketones: 4–100%, C4-ketones: 0–18%, cyclic-ketones: 0–15% and furans: 0–85%. H2 production is favoured at high pressure, elevated temperature, employing a high amount of catalyst and a concentrated lactose solution. Liquid production is preferential using diluted lactose solutions. At high pressure, the production of C3-ketones is preferential using a high temperature and a low amount of catalyst, while a medium temperature and a high amount of catalyst favours the production of furans. The production of alcohols is preferential using medium temperature and pressure and a low amount of catalyst

Production of gaseous and liquid chemicals by aqueous phase reforming of crude glycerol: Influence of operating conditions on the process

The present work studies the influence of the temperature (200-240 °C), pressure (38-50 bar), glycerol concentration (10-50 wt.%) and mass of catalyst/ glycerol mass flow rate ratio (W/mglycerol = 10-40 g catalyst min/g glycerol) during the aqueous phase reforming (APR) of a glycerol solution obtained from the production of biodiesel. The operating conditions exerted a statistically significant influence on the reforming results. Specifically, the global glycerol conversion and the carbon converted into gas and liquid products varied as follows: 4-100%, 1-80% and 16-93%, respectively. The gas phase was made up of H2 (8-55 vol.%), CO2 (34-66 vol.%), CO (0-4 vol.%) and CH4 (6-45 vol.%). The liquid phase consisted of a mixture of alcohols (monohydric: methanol and ethanol; and polyhydric: 1, 2-propanediol, 1, 2-ethanediol, 2, 3-butanediol), aldehydes (acetaldehyde), ketones (C3-ketones: acetone and 2-propanone-1-hydroxy; C4-ketones: 2-butanone-3-hydroxy and 2-butanone-1-hydroxy; and cyclic ketones), carboxylic acids (acetic and propionic acids) and esters (1, 2, 3-propanetriol-monoacetate), together with unreacted glycerol and water. The relative amount (free of water and un-reacted glycerol) of these compounds in the liquid phase was as follows: monohydric alcohols: 4-47%, polyhydric-alcohols: 14-68%, aldehydes: 0-5%, C3-ketones: 2-33%, C4-ketones: 0-10%, ciclo-ketones: 0-6%, carboxylic acids: 2-43%, and esters: 0-46%. This process turned out to be highly customisable for the valorisation of crude glycerol for the production of either gaseous or liquid products. Gas production is favoured at a low pressure (39 bar), high temperature (238 °C), high W/mglycerol ratio (38 g catalyst min/g glycerol) and employing a 15 wt.% glycerol solution. A high pressure (45 bar), medium temperature (216 °C), medium W/mglycerol ratio (22 g catalyst min/g glycerol) and the feeding of a 16 wt.% glycerol solution favours the production of liquid products