a b s t r a c tIn this study, chitosan was extracted from Metapenaeus stebbingi shells. In order to determine physicochemical characteristics of the extracted chitosan, the yield, moisture and ash contents, degree of deacetylation, molecular weight, water and fat binding capacities, apparent viscosity and colour properties were measured using a variety of techniques including Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. In addition, the physicochemical characteristics of the chitosan extracted from M. stebbingi shells were compared to commercial chitosan. The degree of deacetylation was calculated by the titration method and elemental analysis. The molecular weight was determined by viscosimetric methods. The results of the study indicate that shrimp shells are a rich source of chitosan as 17.48% of the shell's dry weight is consisted of this material. Extracted chitosan exhibited a lower molecular weight, higher degree of deacetylation, higher viscosity and higher water and fat binding capacities compared to the commercial chitosan.
Flotation studies were carried out to investigate the removal of heavy metals such as copper (II), zinc (II), chromium (III) and silver (I) from waste waters. Various parameters such as pH, collector and frother concentrations and airflow rate were tested to determine the optimum flotation conditions. Sodium dodecyl sulfate and hexadecyltrimethyl ammonium bromide were used as collectors. Ethanol and methyl isobutyl carbinol (MIBC) were used as frothers. Metal removal reached about 74% under optimum conditions at low pH. At basic pH it became as high as 90%, probably due to the contribution from the flotation of metal precipitates.
We present several
new major features added to the Monte Carlo
(MC) simulation code Brick-CFCMC for phase- and reaction equilibria
calculations (
). The first one
is thermodynamic integration for the computation of excess chemical
potentials (μ
ex
). For this purpose, we implemented
the computation of the ensemble average of the derivative of the potential
energy with respect to the scaling factor for intermolecular interactions
(
). Efficient bookkeeping is implemented
so that the quantity
is updated after every MC trial
move with
negligible computational cost. We demonstrate the accuracy and reliability
of the calculation of μ
ex
for sodium chloride in
water. Second, we implemented hybrid MC/MD translation and rotation
trial moves to increase the efficiency of sampling of the configuration
space. In these trial moves, short Molecular Dynamics (MD) trajectories
are performed to collectively displace or rotate all molecules in
the system. These trajectories are accepted or rejected based on the
total energy drift. The efficiency of these trial moves can be tuned
by changing the time step and the trajectory length. The new trial
moves are demonstrated using MC simulations of a viscous fluid (deep
eutectic solvent).
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