Ultraviolet-activated clamshell hydroxyapatite-substituted palladium in the photoreduction of methyl orange water pollutant.

This study focuses on the modification of natural hydroxyapatite (HAp) derived from clamshell by impregnation with palladium (Pd) at different pH in wet precipitation method to produce photoactive green materials for the degradation of synthetic dyes. It was found that, at pH 10, Pd has been successfully impregnated into HAp lattice with Ca/P ratio of 1.77 and particle distribution size range of 40-470 nm. The impregnation has resulted in the band gap of Pd/HAp at 3.19 eV, as calculated using Tauc's plot from the UV-Vis spectroscopy data of the Pd/HAp. Next, the photocatalytic activities of Pd/HAp were carried out with methyl oranges (MO) as models of water pollutants under UV irradiation. The photodegradation efficiency of the catalyst reached the optimum value of 41.63%, 48.17%, and 43.64% after 120 min of continuous UV irradiation for pH values 8, 10, and 11.5 of Pd/HAp samples, respectively. This study opens a new paradigm in using naturally derived materials as photocatalysts in the reduction of persistent water pollutants at a low cost and green sustainable approach.

Catalytic activity of ethylbenzene with product selectivity by gold nanoparticles supported on zinc oxide.

The oxidation of ethylbenzene (EB) using tert-butyl hydroperoxide as the oxidizing agent was carried out in presence of gold nanoparticles (3 nm) supported on zinc oxide in acetonitrile solution. A higher selectivity towards acetophenone (ACP) as the major product, and a moderate selectivity towards other products such as 1-phenylethanol (PE), benzaldehyde (BZL), and benzoic acid (BzA) were observed using the prepared Au/ZnO nanocatalysts at 100 °C for 24 h. It is suggested the reaction produces an intermediate product, which is dimethylethyl-1-phenylethyl peroxide through a radical mechanism. A small amount of benzaldehyde was observed because benzaldehyde went autoxidation to form benzoic acid with the presence of oxidation agent of TBHP during reaction. The factors affecting the catalytic activity such as gold loading, calcination treatment at 300°C, type of solvent, reaction time, reaction temperature, oxidant to substrate molar ratio, catalyst weight, and solvent volume were studied. The gold nanoparticle catalyst synthesized by deposition precipitation method using urea was characterized by XRD, HRTEM, ATR-IR, XRF, and BET and offers a very selective reaction pathway for the oxidation of ethylbenzene.