A self-regenerating clay-polymer-bacteria composite for formaldehyde removal from water

A multi-functional, self-regenerating material was designed to adsorb and biodegrade formaldehyde from water in a simple, one-step process. The material is based on montmorillonite clay, polyethyleneimine and formaldehyde-degrading Pseudomonas putida, and has three unique functions which facilitate bioremediation: a. selectively adsorbs formaldehyde to reduce cytotoxicity, b. buffers the solution to allow efficient biodegradation, and c. self-cleans through slow release of formaldehyde and subsequent degradation by the attached bacteria, allowing regeneration and long-term use of the material. A polyethyleneimine-clay composite was optimized to carry positive surface charges and a high concentration of functional amine groups, which facilitated formaldehyde adsorption and bacterial adhesion. Formaldehyde binding was specific, yet reversible and pH dependent; binding fitted the Langmuir model and had a q_max of 62 mg·g⁻¹ composite. A formaldehyde-degrading Pseudomonas putida strain was then immobilized on the positively charged composite through electrostatic interactions. The efficiency of the resulting bio-composite was demonstrated for multiple successive treatment cycles, with degradation rates as high as 1600 mg·L⁻¹·FA·h⁻¹. This self-regenerating one-step process is a promising solution to the challenging drawbacks of formaldehyde remediation and could also help design other adsorption-degradation platforms for wastewaters that demand complicated treatment strategies.