Preparation and characterization of montmorillonite membrane for removal of lead and chromium ions from aqueous solutions

• Main Author: A. Talib, Nurul Ain
• Format: Thesis
• Language: English
• Published: 2013
• Online Access: http://psasir.upm.edu.my/id/eprint/38869/1/FS%202013%207%20IR.pdf; http://psasir.upm.edu.my/id/eprint/38869/

Fabrication of membrane from montmorillonite was carried out for removal of metal ions from aqueous solutions. The formation of membrane was optimized based on materials compositions, sintering time and sintering temperature. Montmorillonite KSF (MMT) was used as replacement for the usually expensive materials in membrane fabrication to reduce the cost of production. Each membrane was prepared by suspension of powder materials method. The paste casting was done with different compositions of MMT along with other relatively inexpensive materials which were sand quartz, calcium carbonate, sodium carbonate and boric acid. All membranes were characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption-desorption (BET analyzer) and hardness test. Metal ions concentration in solutions was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Compared to usually high sintering temperature needed in regular preparation of ceramic membrane, this membrane was fabricated at temperature below 1000 °C, which was considered low for inorganic membrane preparation. TGA and DTA results showed that as the sintering time and temperature increased, the thermal stability of membrane also increased. No more degradation of samples was identified after 5 h sintering. By incorporating higher percentages of MMT, the stability of the membranes increased. For samples containing 35% MMT and above, 850 °C sintering temperature was sufficient to produce membranes stable for application up to 1000 °C. The porosity of membrane also increased with sintering temperature. However, as the MMT composition in membrane increased, the porosity decreased due to consolidation of materials at high temperature. Sample 35% MMT sintered at 900 °C was identified as suitable microfiltration membrane based on its maximum pore size 2013 Å (201.3 nm), while main pore distribution was centered at 34.3 Å (3.4 nm) as determined by nitrogen adsorption-desorption analysis. Lead ions were successfully removed from aqueous solution up to 98% by hybridization of adsorption-microfiltration technique at pH 6.1 with 0.8 wt% (w/v) ferric oxide, Fe2O3, as the adsorbent. 92% of chromium ion was also successfully removed at pH 6.0 using the same technique. Other than above metal ions removal, there are also possibilities for separation between metal ion such as Pb2+ ion and Cu2+ ion, and Cr2+ ion and Cu2+ ion. The relatively low cost MMT membrane with sufficient membrane properties is a good material for metal ions removal from aqueous solutions. The hybridization of adsorption-microfiltration technique has high potential application for toxic metal ions removal from wastewater system containing metal waste such as electroplating industrial waste.