How to Quantify the Adsorption of Cyanuric Acid on Activated Carbon Used from Swimming Pool Disinfection?

The physical and chemical characteristics of an adsorbent are key factors determining its efficiency in relation to a particular adsorbate molecule. The adsorption of cyanuric acid (cya) on activated carbon (AC) has not been extensively explored in terms of its basic phenomenon and specific surface interactions. Cya is an important molecule in the swimming pool industry, as it protects free chlorine from UV light degradation. A proper characterization of AC will be beneficial for swimming pool product suppliers to determine the criteria while purchasing it to remove excess cya accumulated in pools. A detailed investigation of the physicochemical properties of activated carbon was conducted to assess its potential to adsorb cya from water. The effect of the adsorption capacity under various pH conditions was studied and it was found that acidic pH favors the adsorption process. With the help of temperature-programmed desorption coupled with mass spectrometry (TPD-MS) and X-ray photoelectron spectroscopy (XPS), the surface chemistry was well analyzed for a proper understanding of the adsorbent-adsorbate interaction. While conventional pool test equipment gives inconsistent readings of the cya concentration, a UV-vis spectroscopy-based methodology has been developed to accurately measure traces of cya in water. This method can be helpful to validate the accuracy of pool-testers for research and development purposes. The batch adsorption experiments revealed that cya adsorption on activated carbon follows pseudo-second-order kinetics, which confirms that the adsorption mechanism is chemisorption, which in fact, depends highly on the surface chemistry of the AC and the reaction pH.

Deep-UV photoinduced chemical patterning at the micro- and nanoscale for directed self-assembly.

Deep-UV (DUV) laser patterning has been widely used in recent years for micro- and nanopatterning, taking advantage of the specific properties of irradiation with high-energy photons. In this paper, we show the usefulness of DUV laser patterning for preparing surfaces with controlled chemical properties at the micro- and nanoscale. Our motivation was to develop a simple and versatile method for chemical patterning at multiscales (from mm to nm) over relatively wide areas (mm2 to cm2). The chemical properties were provided by self-assembled monolayers (SAMs), prepared on glass or silicon wafers. We first investigated their modification under our irradiation conditions (ArF laser) using AFM, XPS and contact angle measurements. Photopatterning was then demonstrated with minimum feature sizes as small as 75 nm, and we showed the possibility to regraft a second SAM on the irradiated regions. Finally, we used these chemically patterned surfaces for directed self-assembly of several types of objects, such as block copolymers, sol-gel materials and liquids by vapor condensation.

Experimental characterization of the nanoparticle size effect on the mechanical stability of nanoparticle-based coatings.

We present an experimental investigation of the mechanical stability of silica nanoparticle-based coatings as a function of the size of the nanoparticles. The coatings are built following a layer-by-layer procedure, alternating positive and negative surface charges. The mechanical stability of the multilayers is studied in water, on the basis of an ultrasonic cavitation test. The resistance of the coating to cavitation is found to remarkably increase with decreasing the size of the nanoparticles, indicating an increase of the cohesive energy density. The relative contribution of van der Waals and electrical double-layer interactions to the stability of the multilayer is discussed toward their size dependence.