Removal of aldehydes by amino acids and their salts in ambient air

The removal of gaseous aldehydes by amino acids and by their sodium salts and hydrochlorides was studied in ambient air with the relative humidity of 30% at 25°C. Amino acid sodium salts, diamino acids, sodium p-aminobenzoate (PABANa), and o-aminobenzoate (OABANa), and p-aminobenzoic acid (PABA) on sepiolite, both having a carboxylato functionality (COO−) together with an amino (NH2) group, were highly reactive with aldehydes. In contrast, PABA which has free carboxylic acid functionality (COOH: dimeric) was not so reactive with aldehydes. Normal amino acids and their hydrochlorides having ammonio (NH2+) and COO− or COOH (dimeric) groups were less reactive with aldehydes. The reactivity was closely related to the degree of dissociation of carboxylate anion; as the degree of dissociation increases, the compound becomes more reactive. p-Aminobenzoic acid hydrochloride (PABA · HCl), having NH3+ and COOH (monomeric) groups, was the most reactive (with ethanal) of all the amino acids and their salts examined. Amino acid sodium salts, diamino acid, PABANa, OABANa, and PABA on sepiolite are proved to be excellent removers of aldehydes in ambient air. Among them, PABA · HCl is particularly good for ethanal.