Proton binding on untreated peat and acid-washed peat

Adsorption of paraquat on soil organic matter: Effect of exchangeable cations and dissolved organic carbon

“…The values of the NICA-Donnan model parameters that describe the distribution of the acid groups in the peat were reported in a previous study [15]. As the negative charge of the peat is due to ionization of the acid functional groups, these parameters can be used to calculate the charge at any pH and ionic strength.…”

“…To remove the inorganic ions, a sub-sample was acid-washed with concentrated HNO 3 at pH 1.0, following a method similar to that proposed by Smith et al [15,16]. The site characteristics and chemical properties of the peat soil are described elsewhere [15], and the most relevant are summarized in Table 1.…”

“…2. Once the value of the charge was determined, the volume of the Donnan phase of the peat, V D [15], was used to calculate the electrostatic potential, « D , created by the charge on the peat. …”

“…Therefore, in order to analyze the effect of exchangeable cations, the adsorption of paraquat on a peat soil was compared with the adsorption on a sample of peat that was first washed in acid to remove inorganic ions. In addition, as Ca 2+ is the most abundant of the exchangeable cations [15], adsorption experiments were carried out with paraquat and acid-washed peat to which different concentrations of Ca 2+ were added.…”

Study of the acid‐base properties of a peat soil and its humin and humic acid fractions

“…Although humin has not so far been considered to contribute significantly to soil organic matter (SOM) behaviour, it can be assumed that the acid‐base properties of the latter will comprise the contribution of the most abundant fractions humin and humic acid. For this reason, in the present study we investigated the proton binding properties of the humin and HA, the latter as a dissolved substance (DHA) and in suspension as aggregated humic acid (AHA), extracted from a peat soil whose proton binding properties have been previously studied (López et al , 2011). This had the following aims: (i) to determine the distribution of acid functional groups, carboxylic and phenolic, in each fraction and analyse their contribution to the acid group distribution in the peat soil and (ii) to calculate the charge in humin and HA and analyse their contribution to the variable surface charge of the peat soil from which they were isolated.…”