Effect of the Addition of Organoclay on the Solubility of Polyvinyl Alcohol Gels Used in the Immobilization of Microorganisms for Wastewater Treatment

This study investigated the effect of the addition of montmorillonite (MMT) organoclay on water solubility of polyvinyl alcohol (PVA) gels, which have been used as an entrapment material in microbial immobilization for biological wastewater treatment. Reduction in the solubility of the PVA gels was proportional to the concentration of organoclay added. Water solubility was reduced to between 83 and 90% on the addition of 1 to 10% organoclay to the PVA gels. However, as the addition of organoclay was increased, it dissolved back into the water phase, which increased the turbidity of the bulk solution. Solubility of the PVA gels decreased with increasing saponification ratio and molecular weight of PVA. Reduction in solubility due to organoclay was compared with the addition of powdered activated carbon (PAC). Organoclay/PVA gels were less water soluble than the PAC/PVA gels, which can be explained by the smaller particle size of the organoclay. Consequently, the reduced solubility caused by the addition of MMT to PVA gels could enhance the applicability of PVA gels to wastewater treatment processes.