Search

Implementing nutrient recycling in wastewater treatment plants is essential for sustainable agriculture. In this study, we investigated a biphasic treatment system for anaerobic liquid digestate, which involved natural and K-enriched zeolite for NH4+ recovery (phase 1), followed by struvite crystallization under two conditions: NH4+ excess and Mg2+ excess (phase 2). The adsorption of NH4+ by natural zeolite enabled saving Mg and P reagents, used to achieve target Mg:NH4:PO4 ratios. The reagent use efficiency of struvite precipitation was highest with natural zeolite under NH4+ excess conditions (96%), whereas the other treatments exhibited lower yields. In this condition, the digestate enriched in Ca2+ released by zeolite; however, no P interferences occurred (Ca2+/Mg2+ < 0.5). Fractions of Ca2+ precipitated as CaCO3. Both the isomorphic NH4- and K-struvite occurred, distinguished by calibrating XRPD data (total struvite) with N contents (indicative of NH4+-struvite). The precipitates comprised NH4- and K-struvite at 60% and 30% (calcite at 9%) in the treatment that involved natural zeolite, 65% and 35% with the K-exchanged zeolite, due to higher presence of K+. Concerning the chemical evolution of the treated digestate, fewer alterations occurred for inorganic ions in the treatment that involved natural zeolite (phase 1) with NH4+ excess condition (phase 2), besides for unreacted SO42– derived from the Mg reagent. The recovered zeolite was enriched in N at 0.5%. Struvite precipitates met the EU regulations regarding permissible levels of organic C, P content, and heavy metal impurities, thereby potentially enabling its use as a fertilizer.Highlights: Zeolites allowed less reagents for reaching optimum struvite precipitation. N loads were reduced with zeolite–struvite treatment up to 86%. Struvite from digestate is usable in agriculture and complied with EU regulations. The precipitation of K-struvite limited the recovery of N from digestate. To discern (K) and (NH4)-struvite, XRD must be combined with chemical information. [ABSTRACT FROM AUTHOR]

Ancient Ardaxšīr Khwarrah, today known as Shahr-e Gur, situated near the modern town of Firuzabad in Fars, Iran, holds historical significance as the inaugural capital city of the Sasanian Empire. During archaeological excavations conducted in 2005 by an Iranian–German team directed by Mas'oud Azarnoush and Dietrich Huff, a mud-brick complex was uncovered, revealing a remarkably well-preserved stretch of wall painting and a polychrome painted floor. The discovery prompted the hypothesis of a potential funerary context dating back to the Sasanian period. Both the wall painting and painted floor have suffered extensive deterioration attributed to the environmental conditions of the archaeological site, which was inscribed on the UNESCO World Heritage List in 2020. To address the urgent need for preservation and further understanding of the site's artistic and structural elements, an emergency diagnostic project was initiated. Non-invasive investigations were carried out on the wall and floor by optical digital microscopy and portable energy-dispersive X-ray fluorescence. Additionally, representative minute samples underwent analysis through various techniques, including micro-X-ray fluorescence, polarised light microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, micro-Raman spectroscopy, micro-Fourier Transform Infrared Spectroscopy, gas chromatography-mass spectrometry and pyrolysis coupled with gas chromatography-mass spectrometry. The palette of the floor and mural paintings were identified to contain red and yellow ochres, lead-based pigments, carbon black and bone white. The unexpected presence of Egyptian blue mixed with green earth was recognised in the green hues of the wall painting. The detection of protein material in both the wall painting and polychrome floor indicates the use of "a secco" technique, thereby shedding light on the artistic practices employed in Ardaxšīr Khwarrah. [ABSTRACT FROM AUTHOR]

This work is the first archaeometric investigation on copper and iron wastes from the Phoenician site of Motya (Sicily, Italy), dating back to the 8th to the 4th century BC. The samples were analyzed through micro‐Raman Spectroscopy (μ‐RS), Optical Microscopy (OM), Scanning Electron Microscope‐Energy‐Dispersive X‐ray Spectroscopy (SEM‐EDS), High‐Resolution Field Emission Scanning Electron Microscopy (HR‐FESEM), and Electron Micro‐Probe Analysis (EMPA). Micro‐Raman techinique permitted to identify both primary phases, for example, calchopyrite, and secondary products such as cuprite and copper thrihydroxychlorides in the Cu‐slags and goethite in the Fe‐slags. SEM and HR‐FESEM imaging showed the occurrence of inhomogeneous microstructures in the Cu‐ and Fe‐slags due to elements segregation, solidification, and corrosion. EMPA data revealed that the archaeometallurgical wastes from Motya can be differentiated on the basis of their chemical compositions. These preliminary results showed different typologies of by‐products, such as base metals speiss, copper slags from smelting sulfide ore with matte, and iron smelting and smithing slags, suggesting different stages of copper and iron productions. [ABSTRACT FROM AUTHOR]