Author : Hala El-Sayed Mohamed Abd El-Razek
Degree : Ph.D. Chemical
Title:
Novel Affinity
Membranes for Wastewater Treatment
Abstract
Affinity membranes have attracted the
attention of membrane researchers especially in the field of wastewater
treatment specifically in removing heavy metals by chelation from aqueous
solutions. In the present work, several membranes made from either cellulose
di-acetate (CA) or CA together with chitosan (CS) solutions, the CS prepared in
our lab from shrimp shells or from readymade shrimp- or crab-shells. The
variables investigated included mass ratio of CA to CS in the casting solution,
initial concentration of Cu(II) ions, type of CS (shrimp- or crab-shells), type
and ratio of solvents forming the casting solutions, type of stirring, stirring
speed and membrane thickness. The membranes were fabricated by casting on a
glass plate of a casting assembly using a doctor’s blade by the phase inversion
technique. The permeation and adsorption capacity of each membrane were
examined in a plexi-glass two compartment diffusion cell in which the membrane
was placed between the two compartments to separate the copper ion solution
from an equal volume of distilled water in the other compartment. The two
compartments were each stirred either magnetically or mechanically. The results
were presented as concentration-time curves and In (Col Ct) vs. time from which
the overall mass transfer coefficient was computed in each case. It was found
that the presence of CS obtained from shrimps acted as a better affinity
membrane in high CA to CS ratios as well as high concentration of Cu(II) ions,
and that crab CS has a poorer affinity to Cu(II) ions compared to that obtained
from shrimps. It was also realized that the composition of the casting solution
markedly affected the properties of the fabricated affinity membrane. In
addition, scanning electron microscopic examination revealed the morphology of
the membrane surfaces (upper, lower and cross section). It is worth mentioning
that membrane thickness has a profound effect on both permeability and extent
of chelation of the heavy metal examined. Later, batch experiments were
conducted to study the kinetics of the adsorption.
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