Chemical Engineering October 2020 - 9

An electrochemical process treats
wastewater from biofuels production
R
esearchers from the School
of Chemical and Biomolecular
Engineering at the Universiy
of Sydney (Sydney, Australia;
www.sydney.edu.au), led by Alejandro
Montoya, have developed an electrochemical
oxidation process to clear
up wastewater, which is heavily contaminated
with organic and inorganic
species during a biofuel production
process, using naturally abundant microalgae.
The electrochemical oxidation
process uses a boron-doped diamond
anode to improve the quality of
the aqueous-phase coproduct from
the
hydrothermal
liquefaction
(HTLACP)
of microalgae Chlorella sp.
According to the researchers, the
oxidation process produced an outstanding
decrease of the chemical oxygen
demand (COD) - ranging from 11
to 185 g/L with a median value of 65
g/L - including the decomposition of
organic nitrogen and the discoloration
of an original brown HTL-ACP. The nitrogen
remains largely as ammonia/
ammonium and nitrates. The deamination
of nitrogenous organic compounds
with subsequent accumulation of NH3/
NH4
- in the HTL-ACP and the partial
oxidation to N2 take place more easily
at lower current density, while the complete
oxidation to NO3
- is more pronounced
at higher current densities.
The HTL-ACP contains between 25
and 50% of the carbon from the feedstock,
as well as nitrogen, phosphorus,
and a variety of ions. The total nitrogen
ranges from 2.3 to 13.6 g/L with ammonia
comprising 20 to 50% of total
nitrogen content and the remaining appearing
mainly as toxic N-heterocyclic
organic compounds.
The researchers say the high variability
of COD and total nitrogen are
associated with the diverse combinations
of HTL process conditions, such
as biomass composition, feed slurry
concentration, temperature, pressure
and residence time. These conditions
define the yield and quality of biocrude
and HTL-ACP properties.
well as multiple sustainability improvements,
including reduced chemical
and energy usage, and production and
shipping efficiencies, says Clariant.
The Johan Sverdrup is one of Norway's
largest oilfields and will, at peak production,
supply 25% of the Norwegian oil
supply. Production started in October
2019 where Clariant was awarded the
production chemical supply contract in
2017 and has been part of the project
phase supporting Equinor in the development
of this giant new oil field.
BIO-BASED PREPOLYMER
Lanxess AG (Cologne, Germany;
www.lanxess.com) has recently developed
a new range of methylen diphenyl
diisocyanate (MDI) polyether
prepolymers containing renewable,
bio-based raw materials. Marketed
under the brand name Adiprene
Green, the products are suitable as
replacement for existing fossil-based
polyether prepolymers to manufacture
highly durable polyurethane (PU)
elastomers. Depending on the system,
a reduction of CO2 between 20
to 30% is possible compared to fossilbased
prepolymers due to the use of
polyether polyols based on starch. 
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CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM OCTOBER 2020
9
http://www.sydney.edu.au http://www.lanxess.com http://www.CHEMSTATIONS.COM/CAKE6 http://adlinks.chemengonline.com/76995-04 http://WWW.CHEMENGONLINE.COM
Chemical Engineering October 2020

Table of Contents for the Digital Edition of Chemical Engineering October 2020
