Immersion enthalpy variation of surface-modified mineral activated carbon in lead (II) aqueous solution adsorption: the relation between immersion enthalpy and adsorption capacity

Abstract

An activated carbon was obtained by chemical activation with phosphoric acid, CM, from a mineral carbon. Afterwards, the carbon was modified with 2 and 5 molL -1 , CMox2 and CMox5 nitric acid solutions to increase the surface acid group contents. Immersion enthalpy at pH 4 values and Pb 2+ adsorption isotherms were determined by immersing activated carbons in aqueous solution. The surface area values of the adsorbents and total pore volume were approximately 560 m 2 .g -1 and 0.36 cm 3 g -1 , respectively. As regards chemical characteristics, activated carbons had higher acid sites content, 0.92-2.42 meq g -1 , than basic sites, 0.63-0.12 meq g -1 . pH values were between 7.4 and 4.5 at the point of zero charge, pH PZC. The adsorbed quantity of Pb 2+ and the immersion enthalpy in solution of different pH values for CM activated carbon showed that the values are the highest for pH 4, 15.7 mgg -1 and 27.6 Jg -1 respectively. Pb 2+ adsorption isotherms and immersion enthalpy were determined for modified activated carbons and the highest values were obtained for the activated carbon that showed the highest content of total acid sites on the surface.

Enthalpies of Immersion in Caffeine and Glyphosate Aqueous Solutions of SBA-15 and Amino-Functionalized SBA-15

“…Recordings were then continued for an additional 10 min, followed by electrical calibration of the calorimeter. Experiments were repeated between three and four times for each solution until a deviation of less than 2% was obtained. − …”

Simple and Competitive Adsorption Study of Nickel(II) and Chromium(III) on the Surface of the Brown Algae Durvillaea antarctica Biomass

“…(i) Immersion enthalpy in water is indicative of the surface chemistry; thus a greater amount of surface-oxygenated groups produces an increase in immersion enthalpy because of the established of interaction between the water molecule and such groupswhich according to the chemical characterization are mostly acid type and interaction with Lewis basic sites, corresponding mainly to the delocalized π electrons aromatic structures. 19,38 (ii) There is an increasing trend in enthalpy values for the chromium solution compared to nickel; this result is the evidence of selectivity and affinity mechanisms through the establishment of different adsorption mechanisms, such as donor−acceptor interactions. 19,38 3.4.4.…”

“…There is an increasing trend in enthalpy values for the chromium solution compared to nickel; this result is the evidence of selectivity and affinity mechanisms through the establishment of different adsorption mechanisms, such as donor–acceptor interactions. 19,38…”

“…Once thermal equilibrium was achieved, the glass bulb was immersed in the solvent; the resulting effect was recorded until a stable baseline was obtained. Recordings were then continued for an additional 20 min after immersion, followed by electrical calibration of the calorimeter …”

“…Recordings were then continued for an additional 20 min after immersion, followed by electrical calibration of the calorimeter. 19 2.6.3. Infrared Spectroscopy.…”