Sorption Characteristics of Mixed Molecules of Glutaraldehyde from Water on Mesoporous Acid-Amine Modified Low-Cost Activated Carbon: Mechanism, Isotherm, and Kinetics

Abstract

The environmental discharge of inefficiently treated waste solutions of the strong biocide glutaraldehyde (GA) from hospitals has potential toxic impact on aquatic organisms. The adsorption characteristics of mixed polarized monomeric and polymeric molecules of GA from water on mesoporous acid-amine modified low-cost activated carbon (AC) were investigated. It was found that the adsorption strongly depended on pH and surface chemistry. In acidic pH, the adsorption mechanism was elaborated to involve chemical sorption of mainly hydroxyl GA monomeric molecules on acidic surface groups, while in alkaline pH, the adsorption was elaborated to involve both chemical and physical sorption of GA polymeric forms having mixed functional groups (aldehyde, carboxyl, and hydroxyl) on acidic and amine surface groups. The optimum pH of adsorption was about 12 with significant contribution by cooperative adsorption, elucidated in terms of hydrogen bonding and aldol condensation. Freundlich and Dubinin-Radushkevich models were fitted to isotherm data. The adsorption kinetics was dependent on initial concentration and temperature and described by the Elovich model. The adsorption was endothermic, while the intraparticle diffusion model suggested significant contribution by film diffusion. The developed low-cost AC could be used to supplement the GA alkaline deactivation process for efficient removal of residual GA aquatic toxicity.

Interaction of Titanium Dioxide with Formaldehyde in the Presence of Quartz Sand under Static and Dynamic Conditions

“…The highest FA sorption was observed at pH 7.5 and the lowest at pH 10. This is consistent with previous studies where at pH < 7, FA removal was reported to increase due to the positively charged hydrogen ion accumulation around the adsorbent surface [63][64][65]. The kinetic experiments of FA sorption onto TiO 2 nanoparticles at solution ionic strengths (Is) of 1, 50, and 100 mM, with FA initial concentration of 5 mg/L and TiO 2 concentration of 100 mg/L, under dynamic and static conditions are shown in Figure 5.…”

“…The highest FA sorption was observed at pH 7.5 and the lowest at pH 10. This is consistent with previous studies where at pH < 7, FA removal was reported to increase due to the positively charged hydrogen ion accumulation around the adsorbent surface [63][64][65].…”

Adsorption studies of divalent, dinuclear coordination complexes as molecular spacers on SWCNTs

“…The shortest incubation time of 10 min was limited by the speed at which the sample could be loaded into the system and reach maximum RPM for the removal of the functionalized SWCNTs. 36 The data also do not represent a diffusion limited model where q t is proportional to t 1/2 . 3.…”

“…These kinetics data are not consistent with common pseudo-firstorder or pseudo-second-order kinetic models. 36 The data also do not represent a diffusion limited model where q t is proportional to t 1/2 . This does not seem to be a diffusion rate limited process.…”