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The open-loop (OL) variant of Kelvin probe force microscopy (KPFM) provides access to the voltage response of the electrostatic interaction between a conductive atomic force microscopy (AFM) probe and the investigated sample. The measured response can be analyzed a posteriori, modeled, and interpreted to include various contributions from the probe geometry and imaged features of the sample. In contrast to this, the currently implemented closed-loop (CL) variants of KPFM, either amplitude-modulation (AM) or frequency-modulation (FM), solely report on their final product in terms of the tip–sample contact potential difference. In ambient atmosphere, both CL AM-KPFM and CL FM-KPFM work at their best during the lift part of a two-pass scanning mode to avoid the direct contact with the surface of the sample. In this work, a new OL AM-KPFM mode was implemented in the single-pass scan of the PeakForce Tapping (PFT) mode. The topographical and electrical components were combined in a single pass by applying the electrical modulation only in between the PFT tip–sample contacts, when the AFM probe separates from the sample. In this way, any contact and tunneling discharges are avoided and, yet, the location of the measured electrical tip–sample interaction is directly affixed to the topography rendered by the mechanical PFT modulation at each tap. Furthermore, because the detailed response of the cantilever to the bias stimulation was recorded, it was possible to analyze and separate an average contribution of the cantilever to the determined local contact potential difference between the AFM probe and the imaged sample. The removal of this unwanted contribution greatly improved the accuracy of the AM-KPFM measurements to the level of the FM-KPFM counterpart.

Various studies were reported for the evaluation of the adsorption performance of kaolin clay using single dye types. This paper aimed to evaluate the comparative adsorption capacity of prepared adsorbents from Ethiopian kaolin for different dye types (Basic Yellow 28 (BY 28), Congo Red (CR), and Reactive Red 120 (RR 120)). Because different dye classes may have a significant impact on the removal efficiency by the prepared adsorbent. Moreover, we intended to investigate the interaction effect of adsorbent-sorbate in the adsorption phenomenon for the three different class dyes. The adsorbents from kaolin clay were prepared via mechanical treatment, beneficiation, and calcination (700 °C). The effect of operating parameters (pH, adsorbent dose, contact time, dye concentration, and adsorption temperature) was evaluated. before and after adsorption of the adsorbents were characterized using FTIR spectroscopy. Furthermore, adsorption isotherm, kinetic models, and the thermodynamic processes in the adsorption phenomenon were computed. The percentage removal efficiency of dyes was recorded as 92.08%, 88.63%, and 73.33% for BY 28, CR, and RR 120 dyes, respectively at the experimental condition: adsorbent dosage = 1 g/100 mL, solution pH = 9 (BY 28), and pH = 3 (CR, and RR 120), contact time = 60 min, initial dyes concentrations = 20 mg/L, and temperature = 30 °C. The adsorption of adsorbates onto kaolin adsorbents was well fitted with pseudo-second-order kinetics and Langmuir isotherm models. The thermodynamic parameters indicate that the adsorption process is spontaneous and exothermic for all dyes. The comparative percentage removal of, with the same operational parameters and kaolin adsorbent, was recorded as BY 28 > CR > RR120 resulting from their surface charge and molecular size/structure dyes properties. We confirm that the adsorption at each operational parameter and peak intensity of FTIR spectra, before and after adsorption, revealed that the different dye types have varied removal efficiency onto the prepared kaolin adsorbent. This is due to that being dominantly influenced by the electrostatic interaction and steric effects at the surface of the sorbent and sorbate characteristics. We deduced that the kaolin clay used as an adsorbent is highly dependent on the dye types and their featured characteristics.

Anionic emulsions are widely used in North America for road maintenance applications but are less popular in Europe. Due to their distinctive characteristics, the use of anionic emulsions is advantageous when local aggregate is excessively dusty and the cost to wash them to meet requirements would be too expensive. However, anionic emulsions’ compatibility, in terms of adhesion, with certain types of aggregate is reported to be limited. This paper presents the results of an experimental study that was conducted firstly to investigate the effect of aggregate mineralogy on the degree of adhesion (i.e. the bond) between the aggregate and the bitumen using anionic and cationic bitumen emulsions, and secondly to evaluate the potential development and use of new adhesion agents/anti-strips for anionic rapid-set emulsions used in chip seal applications. For this purpose, the degree of adhesion that was achieved between the emulsions used and a range of selected aggregates was measured by means of a series of internationally recognised laboratory adhesion tests. The experimental laboratory work confirmed that the degree of adhesion between the aggregate and emulsion is governed to a large extent by aggregate mineralogical composition and, in particular, its associated electrostatic interaction with a given emulsion. The results obtained indicated that a higher degree of adhesion was achieved when an aggregate was combined with an emulsion possessing the opposite surface charge. Further laboratory test results suggest that the addition of amine-based adhesion agents to an anionic emulsion can significantly improve its degree of adhesion with aggregates possessing an electro-negative surface charge.