Adsorption mechanisms of nicotine on humic acid and clay humic acid complex

Abstract

Summary -ZusammenfassungThe adsorption isotherm of nicotine on humic acid -surface was found to be multiphase according to the applied concentrations of nicotine. Each phase was characterized by its own change in free energy and represented a mechanism of interaction. At low concentrations, the isotherm showed a H-curve of high affinity between both reactants as a result of protonation of the pyrrolidine nitrogen atom of nicotine, the second phase was that of flat adsorption in which the nitrogen atoms of nicotine acted as electron donor. The third phase was that of the rearrangement of the nicotine from flat to side adsorption on the humic surface, after which the phase of multilayer formation followed. The adsorption on the surface of the humic acid-clay complex showed no distinct phases but an isotherm looks like the L-type, although it could not verify h g m u i r ' s equation. Probably the isotherm was the resultant of two mechanisms one due to the adsorption of the humic acid part and the other due to the clay part in the complex. Comparison of the constants of Freundlich's equation showed that the capacity of the adsorption humic surface was greater than that of the complex.

Adsorption of Aqueous Nucleobases, Nucleosides, and Nucleotides on Compost-Derived Humic Acid. 2. Naturally Occurring Purines

“…1 All solutes 10-14 were found to interact with HA. 19 Addition of excess nicotine causes fragmentation and dissolution of HA at pH values where HA normally is insoluble. The nucleobase and nucleotide solutes are neutral molecules under these conditions, but the nucleotides are monoanions.…”

“…Equilibrium interaction with the nucleobases and nucleosides gave solutions with pH 5.9-6.6, while the pH with nucleotides 12 and 14 was 3.4-3.7. 19,27,28 None of the other pyrimidine solutes of Part 1 increased the solubility of HA in water at pH's below 8. 22 Dissolution of HA by Adenine.…”

“…8 Secondly, we found that most of the pyrimidine adsorption data could be fitted to the Langmuir model, which generates an adsorption site capacity V i and an equilibrium constant K i (with associated thermodynamic parameters) for each of three adsorption steps A, B, and C. 1 This is significant because thermodynamic data for adsorption on HA are in short supply [9][10][11][12][13][14][15][16][17] and are needed to help us better understand HA properties and functions. 1 Firstly, compost-derived HA has at least three sites A, B, and C 11,17,19 with different site capacities that increase V A < V B < V C . 2, 3,17 The best way to obtain reproducible adsorption data for such materials is to use a large, homogenized sample from a single source.…”

“…[2][3][4][5][6][7] HA's are heterogeneous in the sense that they have either different building blocks or different building block connectivity, depending on the source and HA growth conditions. 19 Fourthly, adsorption of pyrimidines on compost-derived HA is endothermic, thermoneutral, or exothermic, depending on the adsorption site and solute. 1 We studied the adsorption of pyrimidines over wide solute concentration and temperature ranges with three objectives.…”

Measurement of Nicotine in Indoor Air Collected by Alkaline-coated Solid Phase Cartridge Followed by GC-MS Analysis

“…The nitrogen protonation occurs in neutral or acidic conditions. 17) It is believed that protonated nicotine is more adsorptive to the residual silanol groups 18) and more reactive with compounds such as hydroxyl radicals and acidic compounds 19) as compared to free-base nicotine. Therefore, in this study, the modifications to maintain an alkaline condition during the measurement procedure and to prevent the protonation of nicotine were evaluated.…”