Preparation of solid disinfectant for water treatment and mechanism of benzalkonium chloride immobilization on activated carbon

Chlorine disinfection is the most widely used method to inactivate microorganisms in water, however, the byproducts generated after disinfection have a very harmful cumulative effect on human environment. Therefore, a new highly efficient broad-spectrum disinfectant without side-effects is urgently required. Benzalkonium chloride (BAC) can kill bacteria and fungi and inactivate viruses, so it is a dual-function disinfectant. In this paper, BAC molecules were immobilized onto activated carbon (AC), and the mechanism of BAC immobilization was explained at the molecular level. Then, the bactericidal performance of the modified AC was explored. The results showed that AC had a strong adsorption capacity for BAC molecules. The desorption of these BAC molecules from the AC occurred only on the ppm scale. In the immobilization mechanism, the adsorbed BAC molecules agglomerated due to the hydrophobic groups to form large agglomerates. Since the pores of AC are mostly in the shape of ink bottles, it is difficult for these agglomerates to be released from the narrow pore-inlet. The solid disinfectant prepared by fixing different BAC contents in the AC had strong bactericidal performance for Escherichia coli, and the performance was influenced by many factors, including the ability of microorganisms to adsorb onto the BAC-modified AC and the number of free BAC molecules that easily combined with the microorganisms. The bactericidal rate of these solid disinfectants was greater than 95%, and their application to inactivate microorganisms can be used to avoid the disadvantages of chlorine disinfection in water treatment.