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Photocatalytic hydrogen production from alkanol-amines as sacrificial agents by using Cu-modified TiO2–P25 prepared via in situ photodeposition of cupric ions under UV-A light irradiation was investigated. A direct comparison among different sacrificial agents (monoethanolamine, diethanolamine, and triethanolamine) was preliminarily performed. Diethanolamine was selected for further investigation, due to its higher hydrogen production rate with respect to other alkanol-amines. Effect of pH, starting concentration of sacrificial agent, and catalyst/co-catalyst loads were studied. Solution pH exerts major impact on the photoefficiency for hydrogen generation: reaction mechanisms at different pH values were extensively examined. For the first time, a validated kinetic model estimated the unknown rate constants of (i) reaction between diethanolamine and photogenerated holes, (ii) proton reduction, and (iii) diethanolamine adsorption on the photocatalyst surface.

Pd, Rh, Pt are employed in a wide range of applications, such as catalytic converters, fuel cells and electronic devices. In the last years, an increasing pressure on their market was recorded due to a growing demand and limited resources. Therefore, the recovery of these materials from wastes represents an interesting goal to be achieved. The most widely proposed techniques for recovering the palladium from wastes are leaching and ion exchange. Strong oxidizers, acids and high temperature (343–363 K) are used for leaching, leading problems for the environment and the safety. In this work the attention was focused on a system containing zero-valent palladium nanoparticles in which the leaching is performed in mild acidic conditions, by using chloride solutions containing cupric ions (NaCl/CuCl2). The process was studied at varying temperature, pH, chloride and cupric ion concentrations. Good results were obtained at pH 5.0 and temperatures between 288 K and 333 K. The process is more acceptable than the traditional ones from a safety point of view being characterized by less severe conditions (pH and temperatures). A shrinking spherical particles model was adopted to analyse the experimental data from which a development under a kinetic control was demonstrated.

A shortage of market supplies is nowadays recorded for precious metals such as palladium, due to a wide range of applications in which they are used. The development of efficient and inexpensive recovery methodologies of precious metals from waste materials is thus necessary and urgent. In the present study a zinc oxide based photocatalytic system under UV/Visible-light radiation was chosen for palladium (II) deposition from solutions containing it. The effect of ethanol as sacrificial agent was investigated at varying catalyst load, irradiation conditions (UV+visible/visible/dark), metal starting concentration as well as the presence of cupric and chloride ions in solution. Moreover, ZnO dissolution at pH under 6.0 was proposed for the recovery of pure metallic palladium. A network of reactions and a kinetic model were proposed.