OAS and Sheffield presentation - N8 Research Partnership

21 Pages·2012·1.64 MB·English

by  Gareth Wakefield

Methodology Development to Assess Particulate
Agrochemical Diffusion through Soil

Dr Gareth Wakefield – Oxford Advanced Surfaces Group Plc.
Dr Maria Romero-Gonzalez – University of Sheffield
OAS - About Us
Begbroke Science Park – 5 miles north of Oxford.
Mixed Department of Materials/Commercial site
Currently 19 employees
OAS - About Us
• We develop novel materials & license IP / know-how
– global customers can exploit this to develop new products in
next generation materials & products
• Target high-value/high-growth markets in electronics,
green energy and eyewear in two core technologies
– Onto™ patented highly reactive chemistry
– VISARC™ anti-reflective optical coatings utilising OAS MPS particles
• Formed in 2006 – spin-out of Oxford University
– Listed on AIM UK Stock market (OXA)
– ISO 9001:2008 certificated
3
www.oxfordsurfaces.com
Core technologies
OntoTM reactive Chemistry
• Developed at Oxford University over 10 years
• Uniquely reacts with everything
• The power to toughen any material, to adhere to any surface, to
make one chemical surface resemble another.......
• Enabling 21st century products

Nanosized Optical Films
• Transparent surface films 1/1000 thinner than a human hair
• Change the way light passes through surfaces
• The power to stop glass reflecting, to increase solar cell efficiency,
to make lap top screens readable outside........
Technical Challenge
From: Köhne JM, ‘A review of model
applications for structured soils: Pesticide
transport, Journal of Contaminant Hydrology
104 (2009) 36-60
Up to 90% of herbicide never reaches objective
Herbicide Market
2011:

Tonnes 1,080k
Value $18,600M

2016:

Tonnes 1,351k
Value $24,821M
Up to 90% of herbicide never reaches objective
METRC project overview
OAS approached by
OAS can coat particles – but
agrochem Sheffield Group has wide
no experience in agrochem
company – can we coat experience of soil chemistry
or soil transport
herbicides?
OAS Collaborator
• Supply herbicide and formulated control herbicide
OAS
• Coat herbicide and run simple quartz assays
University of Sheffield
• Develop quartz and soil assays
• Run initial greenhouse trials
Technical Challenge
Herbicide particle must:
The ‘collector
1: Hit soil particle (collector) efficiency’

Mechanism of
attachment >
2: Stick to soil particle shear flow
release

Coating allows
3: Release herbicide herbicide
dissolution at
normal rate
Transport of particle through a saturated porous media
Herbicide particle comes into contact with collector (soil model-
quartz) by:

• Interception – Particle moving along streamline hits collector
• Sedimentation – Gravitational settling of particles on to collector
• Brownian motion – Can result in collector contact
Single collector contact efficiency,  =  +  + 
0 D l G
Where  = transport by diffusion
D
 = transport by interception
l
 = transport by gravitation
G
See M. Tufenkji and M. Elimelech, Environ. Sci. Tech., 38 (529-536) 2004
Attachment of herbicide particles to collector particles
Total energy of interaction, G, is given by:
Electrostatic
interaction
y = Distance between collector and particle
Zeta potential, 
k = reciprocal Debye length
1.Herbicide -89mV
2. Quartz -25mV
Zeta potential is key for increasing electrostatic interaction