Enhanced ammonia adsorption and separation by a molecularly imprinted polymer after acid hydrolysis of its ester crosslinker.

Abstract

While ammonia (NH3) is one of the primary hazardous emissions from sludge aerobic composting plants, it has the potential to be recycled as an energy source or nitrogen fertilizer. Recently, an NH3 molecularly imprinted polymer (NH3-MIP) was developed that efficiently separated NH3 from other compounds, but its adsorption capacity required improvement. This study improved both NH3 adsorption capacity and separation of the NH3-MIP using acid hydrolysis optimization. NH3 adsorption capacity increased 13-fold and remained between 5.59 and 7.84\xa0mmol·g-1 during simulated sludge aerobic composting. Separation factors for NH3/methyl sulfide (DMS) (i.e. NH3 adsorption capacity/DMS adsorption capacity) and NH3/dimethyl disulfide both increased more than 15-fold. Results showed that hydrolysis of the ester crosslinker, ethylene glycol dimethacrylate, on the NH3-MIPs produced chemical adsorption sites (‒COOH and epoxides) and increased hydrogen bonds (‒COOH and alcohol hydroxyl), which promoted NH3 adsorption and separation. It is expected that this will be a beneficial strategy for elimination of odors and NH3 recovery during sludge aerobic composting.