Microscopy & Microtechniques
Customising Biochar Morphology Could Herald Great Breakthrough for Environmental Applications
Lorna Campbell, Diamond Light Source, email:
lorna.campbell@
diamond.ac.uk
Work to overcome existing knowledge gaps in the thermochemical decomposition of biomass could enable production of tailor-made bio-chars for high priority environmental applications. This is why the work of Dr Roberto Volpe and his team at Queen Mary University of London, UK is attracting so much interest. He believes that he and his team are the fi rst to get to the bottom of the porosity of biochars. They achieved this in conjunction with colleagues at UCL and in collaboration with Diamond Light Source (Harwell Campus Oxford, UK) who enabled them to image for the fi rst time the porosity of biochars via unprecedented operando experiments at Diamond.
The carbonisation of biomass is a technique that dates back to the beginning of mankind by turning wood into charcoal. However, the full thermo-chemical aspects of this process is still largely unknown. A charcoal-like product known as ‘biochar’ can be produced from agricultural waste. Dr Volpe’s team are working to overcome existing knowledge gaps in the kinetics of pyrolysis and physical activation of biomass. This is because a lack of understanding of how biomass morphology changes during biochar production makes it diffi cult to produce tailor-made bio-chars for specifi c environmental applications.
One conversion method is pyrolysis, a process that involves heating the waste in the absence of oxygen. During pyrolysis, changes in the size and shape (morphology) of particles increase the surface area of the biomass. This surface area controls how biochar binds to (adsorbs) pollutants, speeds up chemical reactions and stores energy.
“What we do is simple. We take almond and walnut shells and we put them through pyrolysis to create a char biomass – the study of carbonisation of biomass essentially refl ects techniques dating back to the beginning of mankind by turning wood into charcoal. However, in our study, the process is monitored every step of the way and what we are interested in, is the porosity that is being created. By accurately heating, we can form up to more than a thousand square metres of accessible surface area in the intricate network of pores inside a single gram of formed biochars,” explained Dr Volpe.
Figure 1. 3D renderings of a single walnut shell particle (in grey) and the pore network (in light blue), before and after pyrolysis - Credit Queen Mary University of London, University College London and Diamond Light Source - I-13
Dr Roberto Volpe in Experimental Hall and Dr Christoph Rau - Principal Beamline Scientist I13 (Images Copyright of Diamond Light Source 2023)
Biochars created from raw biomass of almond
and walnut shells Dr Roberto Volpe’s group, have used Photon and Neutron facilities over the years to work on the development of biochars from agricultural waste. Their current research at Diamond involves examining and identifying the chars created from raw biomass of almond and walnut shells as their porosity during thermo-chemical breakdown is key to unlocking signifi cant technological development.
The ability to customise the morphology of these chars could herald a great breakthrough to help address global challenges by creating inexpensive and renewable solutions for a whole range of applications including: energy storage, catalysis, removing pollutants from water, desalination of water as well as improving quality; soil remediation and reduction of soil emissions of greenhouse gases, reducing nutrient leaching and soil acidity as well as reducing irrigation and fertilizer requirements. Tracking the morphology of biomass during biochar production is the fi rst step towards achieving this.
“Applications for this work are many, as contaminants (bacteria, metals, polluting molecules) or ions (in the case of energy storage) can be carried by water (or by an electrolyte) into the intra-particle pore network and they can be trapped there. Tracking the evolution of this pore network as we heat the biomass particles is key and the real novelty of this work.”
The team chose to use almond and walnut shells as they are more homogeneous compared to other biomasses, so the particles resemble more to each other and are more consistent in their thermal behaviour (hence easier to fi nd robust correlations). Also the lignin content is high, so during heating process they can preserve both the structure and the chemical functionality of lignin which would be more diffi cult to do with ‘softer’ samples. It also allows them a range of tunability that softer biomass does not allow.
Many potential applications including reducing
bacterial contamination in water In terms of applications, the team have already successfully tested bacteria or E-coli adsorption, thereby reducing the bacteria contamination in water by 96% using biochars produced above 500C. Dr Volpe commented; “In general the material can be used for cleaning water from contaminants such as heavy metals, or pharmaceuticals such as anti-biotics or antiseptics. This situation is typical of hospital wastewater and presents a large problem for today’s hospital environment especially in Low and Middle income
INTERNATIONAL LABMATE - APRIL 2023
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
