Separation of Rhodium Catalyst in a Homogeneous System by using Nanofiltration

Nanofiltration process can assist the industry in recovering the catalyst in homogeneous
system. The objective of this dissertation is to report the findings on the research of the
separation for rhodium catalyst in a homogeneous system by using nanofiltration. The
objectives of the research are to determine the solvent-membrane compatibility in a
system, to study the solvent flux and rejection of catalyst in different solvent-membrane
combination and to assess the effect of pressure and concentration towards the catalyst
rejection.
The research starts with the compatibility test which is conducted by soaking the
membrane in solvent for 24 hours to observe any physical changes that occur. The
solvents used are ethyl acetate and toluene while the membranes used are STARMEMTM
122 and STARMEMTM 240. The membranes used for soaking are taken for analysis
using Field Emission Scanning Electron Microscopy (FESEM) to observe the changes
on the surface and the cross section of the membrane after immersing into the solvents.
Stable combinations are used for permeability and rejection study. METcell separation
unit is used to conduct the research for the solvent flux. Three reading for pressure is
used for flux and rejection study which are 10 bar, 15bar, and 25 bar while the
concentration is varied at 0.5 mM, 0.8 mM and 1.0 mM. UV-Visible spectrophotometer
is used to determine the concentration of permeate and the retentate solution for this
research.
STARMEMTM 122 and STARMEMTM 240 changed physically after 24 hours in Ethyl
acetate and no changes observed for both membranes in toluene solvent. From the
FESEM images, changes are observed as well as for all membranes with respect to the
original membranes. During the flux study for pure solvent, it is proven that the flux
declines with time to a steady level which is due to membrane compaction. As the
pressure increases, the solvent flux also increases for both membrane but it is higher for
STARMEMTM 240. Flux reduces with the increase of catalyst concentration which can
be explained by the phenomenon of pore fouling. Rejection is reported high for both
membranes which are around 0.8 to 0.95. In conclusion, nanofiltration is useful in producing green chemical process in industry
especially in optimizing the purity of the products. Pressure and concentration affects
the value of flux and rejection of a system. Prior to conducting the catalyst filtration, the
membrane should be at steady flux condition to avoid unstable permeation. In obtaining,
the right steady flux of system, the process should be done in continuous mode for more
consistent result. The concentration of the rhodium catalyst in the permeate and retentate
solution can be determined using various methods in order to obtain more accurate
result.