Polymer from pyrolysis products

Polymers are used every day; they are an indispensable part of our lives. If we want to maintain our plastic dependant lifestyles and expand our population alternative feedstocks for polymers need to be found. Pyrolysis is a possible route to useful materials however it is difficult to control and analyse the composition of liquid[1] and produce economically viable product[2].Microwave pyrolysis involves lower temperature during pyrolysis and can give more controlled products compared with the conventional method[3].It is anticipated to produce multiple pyrolysis liquids that are potentially input materials for a variety of processes. The focus of this work will be the synthesis of polymers from pyrolysis liquids and how pyrolysis liquid composition affects the behaviour of the product. This work could see a new family of polymers with properties dependant on the composition of pyrolysis liquid. This could help to reduce the use of crude oil for polymers. Please click Additional Files below to see the full abstract

Enhancing evaporative mass transfer and steam stripping using microwave heating

The effect of microwave heating on evaporative mass transfer of hydrocarbons was investigated for a number of contaminated solid materials. The rate of oil removal could be rationalised by the velocity of steam that was created by selective heating of water within the solid. A single correlation was found to fit 45 independent experiments across 10 separate variables, and the correlation was consistent with the physics of evaporative mass transfer. It is shown for the first time that steam stripping is the dominant mechanism that governs hydrocarbon removal during microwave processing. It was further discovered that mass transfer is enhanced due to microwave heating when compared to conventional stripping processes, with this improvement in efficiency due to the ability of the microwave process to overcome the channelling effects that limit conventional mass transfer processes

Understanding Microwave Heating in Biomass-Solvent Systems

A new mechanism is proposed to provide a viable physical explanation for the action of microwaves in solvent extraction processes. The key innovation is Temperature-Induced Diffusion, a recently-demonstrated phenomenon that results from selective heating using microwaves. A mechanism is presented which incorporates microwave heating, cellular expansion, heat transfer and mass transfer, all of which affect the pressure of cell structures within biomass. The cell-pressure is modelled with time across a range of physical and process variables, and compared with the expected outputs from the existing steam-rupture theory. It is shown that steam-rupture is only possible at the extreme fringes of realistic physical parameters, but Temperature-Induced Diffusion is able to explain cell-rupture across a broad and realistic range of physical parameters and heating conditions. Temperature-Induced Diffusion is the main principle that governs microwave-assisted extraction, and this paves the way to being able to select processing conditions and feedstocks based solely on their physical properties. Graphical abstract Keywords Microwave processing, heat transfer, mass transfer, plant cell rupture, cellular expansion mechanics, solvent extractio

Water desalination using a temperature gradient

A new concept for reverse osmosis is identified based on the use of a temperature gradient instead of pressure. When the temperature of the permeate-side of the membrane is higher than the feed-side then a significant driving force exists for water transport, which can overcome the osmotic pressure. The thermodynamics for this approach are developed within the paper, and as a result we have developed a single expression for driving force across a membrane for variable temperature, pressure and concentration. The thermodynamic predictions suggest for seawater a temperature difference of less than 1 o C is needed to overcome the osmotic pressure, and less than 3 o C to sustain a water flux equivalent to current reverse osmosis processes. Experimental investigation confirmed the temperature-dependence of water flux and the ability to carry out reverse osmosis at atmospheric pressure. The effect of temperature gradient and salinity on water flux was tested at ambient pressures and found to be in good agreement with the manufacturer-quoted permeability. The concept identified in this work has the potential to allow reverse osmosis to be carried out without the need for costly high pressure pumps and energy recovery systems, with energy requirements predicted to be lower than 2.0 kWh/m 3

Optimisation of extraction and sludge dewatering efficiencies of bio-flocculants extracted from Abelmoschus esculentus (okra)

The production of natural biopolymers as flocculants for water treatment is highly desirable due to their inherent low toxicity and low environmental footprint. In this study, bio-flocculants were extracted from Hibiscus/Abelmoschus esculentus (okra) by using a water extraction method, and the extract yield and its performance in sludge dewatering were evaluated. Single factor experimental design was employed to obtain the optimum conditions for extraction temperature (25–90 °C), time (0.25–5 h), solvent loading (0.5–5 w/w) and agitation speed (0–225 rpm). Results showed that extraction yield was affected non-linearly by all experimental variables, whilst the sludge dewatering ability was only influenced by the temperature of the extraction process. The optimum extraction conditions were obtained at 70 °C, 2 h, solvent loading of 2.5 w/w and agitation at 200 rpm. Under the optimal conditions, the extract yield was 2.38%, which is comparable to the extraction of other polysaccharides (0.69–3.66%). The bio-flocculants displayed >98% removal of suspended solids and 68% water recovery during sludge dewatering, and were shown to be comparable with commercial polyacrylamide flocculants. This work shows that bio-flocculants could offer a feasible alternative to synthetic flocculants for water treatment and sludge dewatering applications, and can be extracted using only water as a solvent, minimising the environmental footprint of the extraction process

Understanding heat and mass transfer processes during microwave-assisted and conventional solvent extraction

Solvent extraction is a mass transfer process. In this paper, we investigate the role of heat transfer in solvent extraction: in particular, how the heat transfer properties of the solid and the heating method (conventional heating and microwave heating) drive this mass transfer process. Water-based solvent extraction of pectin from orange peel, apple pomace, mango peel and carrot pulp was carried out. The thermal conductivity and dielectric loss were shown as good predictors of extraction performance, with step change increases in mass transfer rates when microwave processing was applied to biomass with dielectric loss significantly higher than water (e.g. 120 mins reduced to 45 mins for optimal pectin extraction from apple pomace). When the loss factor was lower there was no difference in extraction performance between the two technologies (e.g. carrot pulp extraction time was 60 mins in both cases). Further investigations were carried out at different heating rates for both conventional and microwave extraction in order to decouple the effects of microwave volumetric and selective heating. It was shown that below a certain power threshold (within the range of 100 – 120 W in these experiments), microwave and conventional extraction are equivalent, while above the threshold, microwaves achieved a step-change in extraction time. These findings are the first experimental confirmation of recent theoretical advances in microwave biomass processing, in which Temperature-Induced Diffusion drives mass transfer. It is also the first paper to allow identification of biomass characteristics that will be most amenable to microwave extraction

Microwave assisted hydro-distillation of essential oils from fresh ginger root (Zingiber officinale Roscoe)

A solvent free in situ microwave hydro-distillation method for extraction of essential oil from fresh ginger root it presented. Extraction was conducted in a TE10n single-mode microwave cavity and variable power 2 kW generator operating at 2.45GHz. The main extracted components identified by gas chromatography (GC) were Zingiberene, α-Curcumene, β-Sesquiphellandrene and α-Selinene. At energy inputs of 0.40 kWh/kg higher powers and shorter exposure times, crucially did not degrade the highly volatile components (α-Pinene and Camphene) despite providing the highest essential oil yields. Optimum processing conditions were found to be 1000W (0.40kWh/kg) for 5 min, for whole ginger root, where 0.35g oil/100g plant was obtained. This was compared to a yield of 0.2g/100g plant in 150 min in using conventional hydro-distillation and 0.3g/100g plant in 90 min using a multi-mode microwave cavity-based hydro-distillation

Development of a continuous-flow system for microwave-assisted extraction of pectin-derived oligosaccharides from food waste

This paper addresses the current lack of a scalable process for the extraction of “hairy” pectins to upcycle biomasses, by describing the design methodology, building and testing of a continuous microwave-assisted process for potato waste pectin extraction. Hairy pectins have been shown to present prebiotic activity. Conventional pectin extraction methods are not suitable to produce them, as they lead to degradation of hairy regions, in part due to long heating times. Microwave heating is considered an alternative due to its selective and rapid heating. The 2kW single mode system developed in this study achieved good temperature control of ± 2.5°C, and a stable target temperature in ≈1 min processing time at a feed flow rate of 250 mL min-1. Pectin yields of 40 - 45% (indicated by the galacturonic acid content) were achieved, with a feed residence time of only 0.81 s followed by 20 min cooling-down under stirring. These yields were 59.75% higher on average than control experiments in batch conditions or under continuous heating. This indicates that a short heating time is sufficient to allow pectin hydrolysis, after which the rate limiting diffusion step can proceed during cool-down, minimising pectin degradation caused by prolonged exposure to high temperatures. The presence of hairy pectin regions in the extract was confirmed by neutral sugar analysis. The high starch content in potato necessitated a de-starching procedure. A sieving procedure was implemented, which removed more starch than enzymatic de-starching, resulting in a higher purity pectin extract and the ability to collect starch as a separate value stream. This work proves the suitability of microwaves to be used as a fast heating method to extract pectin from biomass, avoiding degradation, using a scalable continuous mode of operation

Current status of microwave-assisted extraction of pectin

There is an urgent need to develop new pectin extraction processes, as the established commercial extraction process damages the pectin (limiting the potential product applications) and is harmful to the environment. Microwave-Assisted Extraction could offer a sustainable route to pectin extraction from a wide range of food wastes and agricultural residues. We present the current state of the art in Microwave-Assisted Extraction of pectin, including the current understanding of the unique heat and mass transfer mechanisms at play during extraction. We review all of the recent literature, testing the commonly held view that microwave heating offers a general improvement in yield and dramatic reductions in processing time compared with conventional solvent extraction. In most of the literature reviewed, there was no evidence that this is the case. However, there is emerging evidence that Microwave-Assisted Extraction can provide processing advantages under some conditions, and that the feedstock dielectric properties and heating rate are important parameters. Preliminary attempts to scale this technology up have shown promise in terms of pectin yield, quality and Life Cycle Analysis compared with conventional extraction. The next steps should be to test more continuous processing concepts for a wider range of feedstocks, and develop more robust Life Cycle Analysis and technoeconomic models. This is the first review paper to focus on the Microwave-Assisted Extraction of pectin

Pb(II) removal using carbon adsorbents prepared by hybrid heating system: Understanding the microwave heating by dielectric characterization and numerical simulation

This work studies the effect of microwaves in the synthesis of carbon adsorbents using pecan nutshell biomass as a precursor in a hybrid multimode microwave cavity avoiding the utilization of chemical activation or susceptors. The dielectric properties were calculated using the cavity perturbation method, and the power distribution of the electromagnetic field inside cavity was obtained by COMSOL Multiphysics. S-350-MW was obtained using at 350 °C and 200 W and it was characterized using elemental analysis, potentiometric titration, FT-IR and nitrogen adsorption isotherms at −196 °C. The adsorption of Pb(II), in single and binary solutions with Cu(II), Cd(II) and Zn(II) in batch systems indicate that the removal of Pb(II) is affected in the presence of Cu(II) due to the competition of these ions as a result of their similarities such as Pauling electronegativity. Finally, the removal of Pb(II) in continuous systems using packed bed columns showed the pH has the most significant effect according to the variance analysis. The finding highlighted the importance of the acidic functional groups in the performance of carbonaceous adsorbents for the removal of Pb(II). Results of this study contribute to the understandings and application of a hybrid heating system and establish the basis of the role of heating processes in the preparation of carbonaceous adsorbents using microwaves. The Pb(II) removal efficiency achieved in this study is significantly higher than the values reported for carbons prepared by using microwave heating which employs susceptors and/or chemical agents reported in literature, demonstrating that it is possible to obtain effective carbon absorbents for the removal of Pb(II) without the use of any additional susceptors or chemical activation