Used water treatment is one of the most important aspects of environmental protection regarding industrial processes. Particulate matter dispersions affect water parameters; for example, increased pH values such as 10.21 are found for used floor tile water, and values of 10.84 are found for used wall tile water. However, pH decreases to about 9.42 after the sediment filtration process. This influences water turbidity, which is higher for used wall tile water due to its finer suspensions, and it is considerably decreased after the filtration process. Thus, the main aim of the present research is to investigate particulate matter dispersion into the water flows that are involved in ceramic tile technological processes before and after treatment at used water treatment facilities. X-ray diffraction (XRD) coupled with mineralogical optical microscopy (MOM) reveals that waters from wall tiles and floor tiles have similar mineral dispersions, containing mineral particles of quartz (5–50 μm), kaolinite (1–30 μm), and mullite (5–125 μm). Glass particles (having a dark appearance at MOM investigation) were also found in both samples in a size range of 20–55 μm. High-resolution SEM imaging coupled with the EDS elemental analysis confirms the XRD and MOM observations. Water samples collected after treatment at the treatment facility reveal a significant reduction in the particulate matter MOM, evidencing only small traces of quartz, kaolinite, and mullite in a size range of 1–15 μm, with most of the particles being attached to the filters, as confirmed by XRD. Atomic force microscopy (AFM) effectuated on this sample reveals the presence of kaolinite nanoparticles with a tabular–lamellar aspect and sizes ranging from 40 to 90 nm. The obtained results prove the efficacy of the filtering system regarding targeted particulate matters, ensuring water recirculation into the technological processes. The sludge resulting from the filtration process presents with a dense grainy structure of sediment particles containing quartz, mullite, and kaolinite, along with traces of iron hydroxide crystallized as goethite. Therefore, it cannot be reused in the technological flux, as the iron causes glaze staining; but the observed microstructure, along with the mineralogical composition, indicates that it could be used for other applications, such as ecological bricks or plasters, which will be further investigated.

Vehicle traffic pollution requires complex physicochemical analysis besides emission level measuring. The current study is focused on two campaigns of emissions measurements held in May and September 2019 in Alba Iulia City, Romania. There was found a significant excess of PM_2.5 for all measuring points and PM₁₀ for the most circulated points during May, along with significant VOC and CO₂ emissions. September measurements reveal threshold excess for all PM along with increased values for VOC and CO₂ emissions. These are the consequences of the complex environmental interaction of the traffic. Street dust and air-suspended particle samples were collected and analyzed to evidence the PM_2.5 and PM₁₀ sources. Physicochemical investigation reveals highly mineralized particulate matter: PM_2.5 fractions within air-suspended particle samples predominantly contain Muscovite, Kaolinite, and traces of Quartz and Calcite, while PM₁₀ fractions within air-suspended particle samples predominantly contain Quartz and Calcite. These mineral fractions originate in street dust and are suspended in the atmosphere due to the vehicles’ circulation. A significant amount of soot was found as small micro-sized clusters in PM_2.5 and fine micro-spots attached over PM₁₀ particles, as observed by Mineralogical Optical Microscopy (MOM) and Fourier Transformed Infrared Spectroscopy (FTIR). GC-MS analysis found over 53 volatile compounds on the investigated floating particles that are related to the combustion gases, such as saturated alkanes, cycloalkanes, esters, and aromatic hydrocarbons. It proves a VOC contamination of the measured particulate matters that make them more hazardous for the health. Viable strategies for vehicle traffic-related pollutants mitigation would be reducing the street dust occurrence and usage of modern catalyst filters of the combustion gas exhausting system.

Ceramic slurry wastes have a significant hazardous potential when dumped. Their recycling as raw material is a sustainable approach for the development of nature-friendly applications. The microstructure and mechanical properties play a key role in the success of this sustainable recycling. Ceramic slurry samples resulting from the wall and floor tiles production facility were analyzed. The mineral composition was investigated by XRD combined with mineralogical microscopy and the microstructure was investigated by SEM microscopy coupled with EDX spectroscopy and elemental mapping. The ceramic slurry contains: quartz, kaolinite, mullite and small amounts of lepidocrocite. Quartz and mullite particles have sizes in the range of 5–100 μm and kaolinite has small particles of around 1 to 30 μm. Iron hydroxide crystallized as lepidocrocite is finely distributed among kaolinite aggregates. It makes the slurry unable to be reused in the technological process because of the glaze staining risk, but it does not affect the material cohesion. Thus, the cylindrical samples were prepared at progressive compactions rates as follows: 1808.55; 1853.46; 1930.79 and 2181.24 kg/m³ and dried. Thereafter, were subjected to a compression test with a lower compression strength of 0.75 MPa for lower density and a higher strength of 1.36 MPa for the higher density. Thus, slurry compaction enhances the kaolinite binding ability. The Young’s Modulus slightly decreases with the compaction increasing due to local microstructure rigidizing. This proves the binding ability of kaolinite, which properly embeds quartz and mullite particles into a coherent and resistant structure. The fractography analysis reveals that fracture starts on the internal pores at low compaction rates and throughout the kaolinite layer in the samples with high compactness. The observed properties indicate that the investigated ceramic slurry is proper as a clay-based binder for sustainable ecological buildings, avoiding the exploitation of new clay quarries. Also, it might be utilized for ecological brick production.

Noise level and atmospheric pollutants such as particulate matter (PM) and combustion gases depend on car traffic. A highly circulated area in Cluj-Napoca City (Romania) was investigated based on sustainable principles. The noise level at the source was about 77 dB due to intense traffic of 214 units/10 min including cars, buses, trucks and pedestrians. It decreased slowly to 62 dB in the proximity of the first wall from the roadside (20 m distance) and significantly to about 50 dB beyond the buildings near the road (135 m from the source). The noise level was correlated with a high pollutant emission at the source: 25 µg/m³ (PM_2.5), 45 µg/m³ (PM₁₀) and 1.023 µg/m³ (total volatile organic compounds (TVOCs)). The PM₁₀ level decreased to 38 µg/m³, while PM_2.5 remained at a high level at 22 µg/m³ and TVOC slightly decreased to 0.974 µg/m³ at the distance of 10 m from the road. The PM_2.5 and PM₁₀ levels decreased significantly to 5 µg/m³ (PM₁₀) and 18 µg/m³ (PM_2.5) at a distance of 135 m from the road, and the TVOC level also decreased significantly to about 0.705 µg/m³. The PM crystalline structure was investigated by XRD coupled with mineralogical microscopy. Microstructure and elemental composition were assessed via high-resolution SEM coupled with EDS spectroscopy. It was found that PM_2.5 was dominated by the finest clay fraction (e.g., kaolinite and muscovite), while PM₁₀ was dominated by quartz and calcite. A large amount of organic matter was found adsorbed onto the finest particles by FTIR spectroscopy. The correlation between PM emissions and sound intensity indicates that intense noise extended for a long time facilitates the ultra-structural PM fraction sustentation into the atmosphere. A large number of clay nanoparticles (kaolinite 40 nm and muscovite 60 nm) were detected by AFM in the samples collected at the noise source, becoming sparser at a distance of 135 m from the source.

Ferrous particles are usually found in atmospheric particulate matters due to the cars chassis oxidation. These particles are able forming conglomerates with the other mineral particles. Thus, the investigated carwash slurry (CS) reveals a high mineralized composition dominated by Quartz, Calcite and clay minerals with significant amount of iron hydroxides. We found some unusual bigger particles of ferrous conglomerate (FC) into the CS sample. XRD and mineralogical microscopy (MOM) reveal that FC sample is formed by a nanostructured mixture of 56 wt.% Calcite and 44 wt.% Goethite. SEM images and EDS spectra reveal submicron particles within the FC structure with a dense mixture of Ca and Fe. FTIR investigation reveal strong absorption bands for goethite and very weak ones for Lepidocrocite within the FC sample. The results indicates that the conglomerate weas formed on the car chassis rust by wet partial dissolution of calcite that locally forms Ca(OH)2 which further is re-crystallized as calcite due to the CO2 from the combustion gases. Fine crystallites of iron hydroxides are embedded into the re-crystallized calcite. In conclusion, the magnetic selection is recommended for the ferrous conglomerate particles removal from CS to be used as natural coverage for of urban dump sites rehabilitation.

Kaolinite is able to assure the high binding affinity of the filler particles of raw ceramic bodies. It acts as a matrix that strongly holds the other constituents’ particles in a compact structure. The slurry samples were characterized by XRD, mineralogical microscopy and SEM coupled with an EDX elemental analysis. The slurry collected from the ceramic tile production wastewaters had a significant amount of kaolinite (36%), mostly fine particles of 3 µm, less surrounding quartz (37%) and mullite (19%) particles of 5–100 µm in diameter and traces of lepidocrocite (8%). It is a dense paste with a relative moisture of 25%. The square bar of the slurry as received, pressed at a load of 350 N, had a flexural strength of 0.61 MPa. Increasing the moisture to 33% using regular water, followed by mechanical attrition at 2000 rpm for 5 min, resulted in a porous bar with a flexural strength of 0.09 MPa; by increasing the attrition speed to 6000 rpm, the microstructural homogenization was improved and the flexural strength was about 0.68 MPa. It seems that regular water does not assure an optimal moisture for the kaolinite matrix conditioning. Therefore, we used technological water at pH = 10, a moisture of 33% and attrition at 6000 rpm for 5 min, and the bar pressed at a load of 350 N had a flexural strength of 1.17 MPa. The results demonstrate that the bar moistened with technological water and an attrition regime assured a proper conditioning for the kaolinite matrix, achieving the optimal binding of the quartz and mullite particles under the pressing load. Bars with the optimal mixture were pressed at several loads, including 70, 140, 210 and 350 N, and the flexural strength was progressively increased from 0.56 MPa to 1.17 MPa. SEM fractography coupled with atomic force microscopy (AFM) revealed that the optimal moisture facilitated a proper kaolinite particle disposal regarding the quartz and mullite filler particles, and the progressive load assured the strong binding of the finest kaolinite platelets onto their surface.