A model, including the chemical details
of core nanoparticles as
well as explicit surface charges and hydrophobic patches, of triblock
Janus particles is employed to simulate nucleation and solid–solid
phase transitions in two-dimensional layers. An explicit solvent and
a substrate are included in the model, and hydrodynamic and many-body
interactions were taken into account within many-body dissipative
particle dynamics simulation. In order not to impose a mechanism a
priori, we performed free (unbiased) simulations, leaving the system
the freedom to choose its own pathways. In agreement with the experiment
and previous biased simulations, a two-step mechanism for the nucleation
of a kagome lattice from solution was detected. However, a distinct
feature of the present unbiased versus biased simulations
is that multiple nuclei emerge from the solution; upon their growth,
the aligned and misaligned facets at the grain boundaries are introduced
into the system. The liquid-like particles trapped between the neighboring
nuclei connect them together. A mismatch in the symmetry planes of
neighboring nuclei hinders the growth of less stable (smaller) nuclei.
Unification of such nuclei at the grain boundaries of misaligned facets
obeys a two-step mechanism: melting of the smaller nuclei, followed
by subsequent nucleation of liquid-like particles at the interface
of bigger neighboring nuclei. Besides, multiple postcritical nuclei
are formed in the simulation box; the growth of some of which stops
due to introduction of a strain in the system. Such an incomplete
nucleation/growth mechanism is in complete agreement with the recent
experiments. The solid–solid (hexagonal-to-kagome) phase transition,
at weak superheatings, obeys a two-step mechanism: a slower step (formation
of a liquid droplet), followed by a faster step (nucleation of kagome
from the liquid droplet).
The present research introduces adsorption of sulfonated cobalt phthalocyanine catalyst (Europhtal) from the real wastewater that is produced by the mercaptan removal unit (Merox) of the third refinery, South Pars Gas Complex (SPGC), Assaluyeh, Iran. Therefore, novel low-cost natural zeolite modified with polyaluminium chloride (PAC) was investigated as an adsorbent for the treatment of Europhtal wastewater. Central composite design (CCD), as a set of response surface methodology (RSM), was applied to acquire optimum operational conditions such as contact time, pH, adsorbent dosage, and Europhtal concentration. Results showed that the removal percentage of Europhtal in the real wastewater was 93.4% at best operating condition consisting of a pH of 6.7, sonication time of 8 min, 0.035 g of adsorbent. The obtained results were evaluated by adsorption isotherms and kinetic parameters. It was found that the equilibrium data matched the Freundlich model acceptably, with the maximum experimental adsorption capacity of this model was 687.51 mg g-1 at 301.15 K. From the kinetic data, it was revealed that the adsorption process followed the pseudo-second-order kinetic model. Furthermore, the obtained thermodynamic parameters such as ∆H°, ∆S°, and ∆G° imply the endothermic essence of adsorption proceeding spontaneously.
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