This
work reports the preparation of a novel class of lignin reverse micelles
(LRM) and their application as a UV-blocking additive for thermoplastics.
It is found that when 7 vol % cyclohexane was added into alkali lignin
(AL)/dioxane solution, LRM formed. When the cyclohexane amount increased,
LRM tended to aggregate and separate from the solutions. LRM films
had a water contact angle higher than 80°, in comparison to only
52° of the AL film control sample. Due to hydrophobicity, the
miscibility of LRM with high density polyethylene (HDPE) was significantly
improved from that of AL with HDPE. Since LRM retained the phenolic
hydroxyl structure of AL, the HDPE/LRM samples showed an excellent
UV-absorbing performance. Furthermore, the added LRM had little negative
influence, but significantly improved the HDPE mechanical properties.
With 5 wt % LRM loading, Young’s modulus increased from 1066
to 2104 MPa and the elongation at break increased from 671% to 1030%,
respectively.
Sodium lignosulfonate reverse micelles
(SLRMs) with vesicular structure
were prepared by self-assembling in ethanol–water media and
applied to encapsulate horseradish peroxidase (HRP). Results showed
that sodium lignosulfonate (SL) could not form SLRMs until the ethanol
content reached 63% when its initial concentration was 7.5 g L–1. Owing to strong electrostatic repulsion, solid spherical
SLRMs gradually swelled to stable vesicular structures with an average
size of 240 nm. The shell of the SLRM thickened when NaCl was added
to screen the electrostatic interaction. HRP can be effectively encapsulated
while retaining its activity in the hydrophilic core of a SLRM. When
hydrogen peroxide was added to initiate the catalytic activity of
HRP, SL molecules would be polymerized and the structure of SLRMs
would be fixed. Furthermore, HRP immobilized in polymerized SLRMs
showed high activity at a more acidic pH of 4 and at a lower optimal
temperature decrease of 35 °C compared to free HRP. SLRM allows
enzymes such as HRP to work at more acidic and lower temperature conditions.
An efficient and stable catalyst
to produce higher alcohols with
a higher heat value and cetane number and less corrosive to engines
from aqueous ethanol is still facing challenges. Here, a novelty of
NiSn bimetallic catalysts encapsulated in a nitrogen-doped lignin-based
carbon material (NiSn@NC) was prepared by modified biorefinery lignin
and further precisely coordinated with metal ions to form a lignin-metal
supramolecular material followed by in situ calcining. Results showed
that the optimized Ni20Sn1@NC catalyst exhibited
a superior ethanol conversion (68.5%), a C4+ higher alcohol
yield of 31.8%, and a ratio of iso to normal alcohol of 0.52. Moreover,
it also exhibited excellent stability even after four-cycle runs.
Structural analysis revealed that the Sn/N-doping lignin-based carbon
material improved the Ni dispersion and basic site density, which
adjusted efficiently the electronic structure of the metallic active
site. Therefore, the NiSn@NC bimetallic catalysts showed satisfactory
conversion and stability of aqueous ethanol upgrading to C4+ higher alcohols.
Membrane distillation (MD) and freeze crystallizer (FC) were evaluated as alternative reverse osmosis concentrate (ROC) treatment options. A direct contact MD (DCMD) was capable of obtaining 60% water recovery with chemically pretreated ROC. Nevertheless, in repeated cycles, DCMD displayed a trend of reduced water recovery and declining permeate quality. At elevated concentrations, ROC caused scaling and membrane hydrophobicity reduction, indicating reduced membrane life span. On the other hand, FC in three-stage freeze/thaw approach was able to concentrate ROC by 2.3 time, achieving a 57% water recovery with no scaling issues. The fresh ice water quality (total dissolved solids) obtained from FC was within the range of 0.08-0.37 g/L. A brief techno-economic evaluation highlighted advantages and limitations of both options. The efficiency of DCMD as a compact, low thermal process for ROC treatment was compromised by membrane scaling, indicating the necessity for a scaling mitigation pretreatment. This invariably incurs an additional cost. FC was advantageous as a scaling and chemical free process. The high freezing requirement of FC could be met by coupling with refrigerant coolant from liquefied natural gas. Nevertheless, the practical industrial application of FC is inherently restricted due to complex scaling up issues.
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