Self-Regenerating Bio-Silicates for Adsorption and Degradation of Pollutants

Adi Radian, Civil and Environmental Engineering, Technion - Israel Institute of Technology, Haifa, Israel

Widespread pollution of water and soil are among the greatest challenges we face today. Yet, most remediation strategies offer only a partial solution; requiring follow-up steps to regenerate the system and leaving concentrated byproducts that need further processing. Developing self-regenerating materials that remove and biodegrade pollutants is therefore highly advantageous. Presented here are examples of such materials, where biodegradation is enhanced by immobilizing and encapsulating bacteria on specially tailored functionalized silicates:

• An Amine-functionalized silica gel was developed to protect encapsulated cells from bleach oxidation. Tricloro is a widely used water disinfectant that generates bleach and the byproduct cyanuric acid. Removal of this byproduct is crucial for safe disinfection and can be achieved with certain soil microorganisms. However, these microorganisms are susceptible to the Tricloro whose job is to kill them. The proposed bio-silica could degrade cyunaric acid in conditions ten-fold more toxic than free cells in solution.
• A phenyl-functionalized silica-gel, containing hydrophobic microspherical patches with adhered biodegrading bacteria, was developed to remove hydrophobic herbicides from water. The microspherical patches were able to concentrate the pollutants in the silica gel and facilitated their diffusion to the adhering degrading bacteria - constantly freeing up binding sites and regenerating the material.
• A bio-clay was designed to rapidly yet reversibly adsorb formaldehyde (FA) which is then degraded by co-localized bacteria. The immobilization protects the bacteria from high FA concentrations and low pH, allowing efficient remediation. The adsorption-degradation combination also allows the material to self-regenerate by freeing-up new FA-binding sites, enabling long-term continuous use. The proposed material is based on soil extracted FA-degrading bacteria immobilized on a polycation–clay composite.

The examples given here show the advantages of immobilizing bacteria on specially tailored surfaces which either protect from toxicity or increase substrate concentration to allow more efficient degradation and long term-use of the material.