Physico-chemical characterization of activated carbon–metal oxide photocatalysts by immersion calorimetry in benzene and water

Abstract

From a commercial activated carbon (AC) and Al 3? , Fe 3? , Zn 2? , SnCl 2 , TiO 2 and WO 4 2in water, three series of AC-metal (hydr)oxide (MO) samples prepared by wet impregnation in two successive steps of soaking at 80 °C and oven-drying at 120 °C (S1) and subsequent heat treatment at 200 (S2) or 850 °C (S3) were characterized texturally by N 2 adsorption at -196 °C and by immersion calorimetry in benzene and water. The mass changes associated with the preparation of the samples are usually stronger for S1 and S3 than for S2. The incorporation of MO to AC causes a greater decrease in the micropore volume and pore narrowing only for the SnCl 2 -impregnated sample. The opposite effects on the microporous structure are noted for most S2 and S3, as compared to S1. For AC, -D i H(C 6 H 6 ) is 114.0 J g -1 and -D i H(H 2 O) is 30.5 J g -1 . For the AC-MO samples, -D i H(C 6 H 6 ) and S tot (C 6 H 6 ) are generally lower than for AC and vary by S3 [ S2 [ S1. However, -D i H(H 2 O), S tot (H 2 O) and [O] are usually lower for S3. S tot (C 6 H 6 ) is higher for the samples prepared using the metal ions. The results of immersion calorimetry for AC and AC-MO samples provide one with valuable information concerning the dependence of the hydrophobicity and hydrophilicity of the samples on the method used in their preparation.

Microcalorimetry Techniques for Studying Interactions at Solid–Liquid Interface: A Review

“…This concept has been widely accepted and acknowledged by many researchers. Bogeat et al [44] immersed activated carbon in solutions with various ions to prepare samples coated with metal oxides and found the number and type of hydrophilic groups (functional groups containing oxygen on the activated carbon surface (like hydroxyl, carboxyl, and ketone groups) and coordinating groups and polarized bonds, such as metal-oxygen bonds in metal oxides) in the samples affected their affinity for water. Samples with more hydrophilic groups showed a stronger affinity for water, implying that activated carbon with more hydrophilic groups has higher immersion enthalpies in water.…”

Microcalorimetry Techniques for Studying Interactions at Solid-Liquid Interface: A Review

“…When measuring immersion enthalpy as a function of degassing temperature, they observed similar trends in both systems and the immersion heat in non-polar benzene was virtually unaffected by the removal of surface groups during thermal treatment. Acevedo et al [43] chemically activated African palm shells to produce activated carbon and introduced the concept of a "hydrophobic factor," which is defined as the ratio of the immersion enthalpy in benzene to that in water. It was observed that the immersion enthalpies of the activated carbon in benzene and dichloromethane were significantly higher than those in water, which indicates a strong hydrophobic character of the produced activated carbon.…”

Calorimetry of Immersion in the Energetic Characterization of Porous Solids

“…Stoeckli et al use this technique to characterize the porous structure of a wide variety of carbonaceous materials taking a non-porous carbon black as a reference, assuming that the immersion enthalpy per surface area is proportional to the available surface to the immersion liquid [24].…”