(469e) Bimetallic Nanoparticle Impregnated Surface Modified Activated Carbon for Application in Continuous Water Disinfection | AIChE

(469e) Bimetallic Nanoparticle Impregnated Surface Modified Activated Carbon for Application in Continuous Water Disinfection

Authors 

Das, A. - Presenter, Indian Institute of Technology Bombay, Powai
Bandyopadhyaya, R., Indian Institute of Technology Bombay
The pressing global concern of providing safe drinking water is anticipated to worsen over the next decade due to the proliferation of pathogenic microorganisms and the emergence of antibiotic-resistant strains. Conventional centralized disinfection methods in urban areas, like chlorination, have drawbacks, such as generation of carcinogenic and mutagenic by-products. On the other hand, UV and membrane-based systems need significant capital requirements for operation; however, there is still a possibility of re-contamination during supply to the point of use (POU). Therefore, affordable POU water disinfection systems that can operate without electricity are urgently needed, especially in developing nations and regions afflicted by natural disasters where power infrastructure is often compromised. In this context, activated carbon (AC) finds widespread application in water disinfection systems, mainly attributed to its large surface area. With its significant adsorption capacity, AC effectively eliminates organic compounds, heavy metals, and a diverse range of contaminants that impart taste, colour, and odour to water; however, it can’t eliminate bacteria.

Recent research shows impregnation of monometallic nanoparticles (silver, copper, gold, and titanium oxide) with well-established bactericidal properties onto AC for continuous water disinfection. More recently, combining monometallic particles to synthesize bimetallic counterparts has attained significant attention, offering tailored properties distinct from those of individual monometallic systems. This work explored bimetallic silver-copper nanoparticle (BMNP) impregnated on coconut shell-derived AC for possible superior bactericidal activity in a column-based system to facilitate continuous water disinfection.

Primarily, spherical BMNP were synthesized through a galvanic replacement reaction route using non-hazardous chemical reagents. Transmission electron microscopy (TEM) showed an unimodal size distribution of the particles with spherical morphology, and energy-dispersive X-ray spectroscopy (EDX) analysis verified a blended distribution of Ag and Cu atoms within individual particles. These nanoparticles were then impregnated onto the surface of AC with varying degrees of base functionalization. The generation of polar hydrophilic functional groups on base-treated AC was confirmed using FTIR spectroscopy, which facilitated the attachment of NP on AC. Successful impregnation of nanoparticles onto the AC surface was confirmed by observing characteristic FCC peaks in the X-ray diffraction (XRD) spectra for both Ag and Cu. The bimetallic NP-AC composite achieved a maximum loading of 3 wt.% Cu and 2 wt.% Ag, as measured using ICP-AES.

Batch mode experiments conducted in shake flask demonstrated that the composite was capable of 4 log reduction of E. coli cells in only 15 minutes of contact time, which was 2 and 1.6 times faster as compared to monometallic Cu-impregnated AC and monometallic Ag-impregnated AC, respectively. Furthermore, the increasing concentration of reactive oxygen species (ROS) over time verified bacterial cell death was attributed to the synergistic generation of ROS species by both Ag and Cu ions. The efficacy of the composite was further tested in a practical scenario within a continuous flow setup, packed inside a cylindrical column, typically as found in commercial household water purification systems. Studies revealed that the composite continuously eliminated 104 CFU/ml bacterial load in the simulated contaminated water successfully for at least 460 hours, yielding a minimum of 25 litres of potable water without attaining breakthrough. Simultaneously, the concentration of both Ag and Cu ions in the treated water remained within permissible limits, as prescribed by the USEPA and WHO. Thus, the developed bimetallic NP-impregnated AC composite exhibited promising antibacterial efficacy, providing an efficient solution for disinfecting water contaminated with E. coli and highlighting its potential to address water quality challenges in remote and disaster-affected areas.