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Eco‐friendly catalysts have been obtained by functionalizing hydroxyapatite (HAP) with iron (Fe/HAP), according to three preparative methods (flash ionic exchange, deposition‐precipitation, and impregnation). Fe/HAP samples (ca. 2–7 wt.% Fe) have been tested in the reaction of NOx reduction by ammonia (NH3‐SCR) in the 120–500 °C interval with different NH3/NO ratios (0.6–2) at fixed contact time (0.12 s). All Fe/HAP samples were active and selective in the NH3‐SCR reaction starting from ca. 350 °C. Better performances have been observed on catalysts prepared by deposition‐precipitation and impregnation (about 70 % of NOx conversion and selectivity to N2 higher than 95 % at 350 °C), where α‐Fe2O3 and 3D‐Fe2O3 nanoclusters were present, as indicated by Mössbauer and UV‐Vis‐DR spectroscopies. On the opposite, paramagnetic Fe3+ centres were the predominant species on samples prepared by flash ionic exchange. Further characterization techniques (XRPD, N2‐physisorption, acidity by NH3 adsorption, and H2‐TPR) have concurred to elucidate Fe‐sitting HAP and structure‐activity relationships.

Furfural is a high-value chemical, being the precursor of compounds such as furfuryl alcohol and tetrahydrofurfuryl alcohol. Pt is known as active for furfural hydrogenation, but the high price limits its exploitation and imposes the search for alternatives. Here we presented a Pt/Mo bimetallic system with enhanced catalytic activity for furfural hydrogenation. For comparison, monometallic Mo-and Ptsupported on activated carbon have been prepared by impregnation and sol-immobilization. The bimetallic Pt/Mo was prepared impregnating the Mo-AC catalyst with Pt, using Na 2 PtCl 4 as a precursor, PVA, and NaBH 4 as reducing agent. HR-TEM analyses on Pt/Mo catalyst showed Mocontaining agglomerates embedded in the carbon matrix, displaying diffraction fringes with spacing typical of Mo 4 O 11 in the orthorhombic phase, as well as Pt nanoparticles more evenly dispersed in the Mo-AC system compared to bare AC. The Pt/Mo catalyst showed higher activity than both monometallic ones, and it converted 92 % of furfural to furfuryl alcohol and ethyl furfuryl ether with 20 % and 80 % selectivity, respectively. However, despite a lower initial activity, the monometallic Mo/AC catalyst showed a complete selectivity to the ether.

A series of iron functionalized hydroxyapatite (Fe/HAP) samples with different metal loading (2 < wt.% Fe < 13) was prepared by a flash ionic exchange procedure from iron(III) nitrate as precursor and tested in some environmental air-quality protection reactions such as the catalytic reduction of NOx by NH3 (NH3-SCR), catalytic oxidation of NH3 (NH3-SCO) and catalytic N2O decomposition. The catalytic performances of the Fe/HAP catalysts were determined under flow conditions as a function of temperature and using reactant concentrations typical of polluting gaseous emissions from industrial vents. Physico-chemical characterization with various techniques of study (UV-DR and Mössbauer spectroscopies, NH3 titration, N2-physisorption, and XRPD analyses) provided valuable information on Fe-speciation, acidity, morphology, and structure of the samples. In general, highly dispersed Fe3+ centers were the predominant species, irrespective of Fe-loading, while just low percentage (≤15%) of FexOy nanoclusters (2 < size/nm < 4) was detected on the samples. As expected, the differences in iron concentration produced a diversified effect of both catalyst properties and catalytic activity, comprising the conversion and selectivity profiles, different for each reaction considered. The obtained results indicate a good potentiality for the eco-friendly Fe-catalysts for some environmental reactions of air protection.

Olive oil production in Mediterranean countries represents a crucial market, especially for Spain, Italy, and Greece. However, although this sector plays a significant role in the European economy, it also leads to dramatic environmental consequences. Waste generated from olive oil production processes can be divided into solid waste and olive mill wastewaters (OMWW). These latter are characterized by high levels of organic compounds (i.e., polyphenols) that have been efficiently removed because of their hazardous environmental effects. Over the years, in this regard, several strategies have been primarily investigated, but all of them are characterized by advantages and weaknesses, which need to be overcome. Moreover, in recent years, each country has developed national legislation to regulate this type of waste, in line with the EU legislation. In this scenario, the present review provides an insight into the different methods used for treating olive mill wastewaters paying particular attention to the recent advances related to the development of more efficient photocatalytic approaches. In this regard, the most advanced photocatalysts should also be easily recoverable and considered valid alternatives to the currently used conventional systems. In this context, the optimization of innovative systems is today’s object of hard work by the research community due to the profound potential they can offer in real applications. This review provides an overview of OMWW treatment methods, highlighting advantages and disadvantages and discussing the still unresolved critical issues.