(548s) Environmental Impact Assessment for High Conversion Synthesis of <10 Nm Silver Nanoparticles Using Microwave Assisted Heating By Life Cycle Techniques

Environmental impact assessment for
high conversion synthesis of <10 nm silver nanoparticles using microwave
assisted heating by life cycle techniques

Adarsh Bafana¹, Shishir Kumar¹, Prasad Pawar¹, Sila Temizel-Sekeryan², Si Amar Dahoumane³,
Liv Haselbach², Clayton Jeffryes^1,*

¹Nanobiomaterials and Bioprocessing
Laboratory (NABLAB), Dan F. Smith Department of Chemical Engineering, Lamar
University, Beaumont, TX 77710

²Department of Civil and
Environmental Engineering, Lamar University, PO Box 10024, Beaumont, TX 77710,
USA

³School of Biological Sciences &
Engineering, Yachay Tech University, Hacienda San
José s/n, San Miguel de Urcuquí 100119, Ecuador.

*Corresponding Author:
cjeffryes@lamar.edu

Abstract:

A microwave reaction to
convert 99 ± 1% of Ag⁺ to silver nanoparticles (AgNPs)
of size <10 nm within 4.5 min with a specific production rate
and energy input of 5.75 mg AgNP L⁻¹ min⁻¹
and 5.45 W mL⁻¹ reaction volume was developed. The
glucose reduced, and food grade starch stabilized particles remained
colloidally stable with less than a 4% change in the surface plasmon resonance
band at 425–430 nm at t > 300 days. TEM determined the
size of AgNPs, while TEM-EDS and XRD verified elemental composition. The
conversion was determined by inductively coupled plasma atomic emission
spectroscopy (ICP-AES) and thermal gravimetric analysis (TGA). Additionally,
the required silver to starch input mass ratio, 1.0:1.3, to produce colloidally
stabilized AgNPs is significantly reduced compared to previous studies. The
antibacterial activity of freshly prepared AgNPs and AgNPs aged >300 days
was demonstrated against E. coli as determined by agar diffusion
assays. This result, corroborated by spectrophotometric and TEM measurements,
indicates long-term colloidal stability of the product. We attempted novel synthesis routes
that reduce resource requirements and use benign chemicals, while maintaining
control over their unique properties. Thus, we evaluated the potential environmental
impacts of this method using Life Cycle Assessment (LCA) techniques which are
used to assess the environmental impacts of a product’s life through all the
stages from raw material extraction to disposal/ recycling. GaBi 6.0 software
was used to carry out the life cycle impact assessment on a declared unit of 1
kg of 3.0 ± 1.2 nm diameter AgNPs. The results indicate that the impacts are
predominantly on acidification (AP), human health particulate air (HHAP) and
human toxicity non-cancer (HTNCP) potentials. These impacts are mainly from the
production of silver metal and electricity used. The starch and glucose used to
produce AgNPs of 3.0 ± 1.2 nm appear to be environmentally benign as they have
negligible environmental impacts.