Search Results (9)

To improve the machinability properties of CuZn-alloys, these are alloyed with the element lead. Due to its toxicity, a variety of legislative initiatives aim to reduce the lead content in CuZn-alloys, which results in critical machinability problems and a reduction in the productivity of machining processes. Basically, there are two ways to solve the critical machinability problems when machining lead-free CuZn-alloys: optimizing the machinability of lead-free materials on the material side or adapting the processes and the respective process parameters. In this study, the focus is on material-side machinability optimization by investigating the influence of a targeted variation in the process chain in the material production route. To evaluate the influence of the material production route, the brass alloy CuZn40 (CW509L) was produced in four variants by varying the degree of work hardening and the use of heat treatments, and all four variants were evaluated in terms of their machinability. To evaluate the machinability, the cutting force components, the chip temperature, the chip formation, and the chip shape were analyzed. Clear influences of the material production route were identified, particularly with regard to the chip formation mechanisms and the resulting chip shape. Full article

This study aimed to assess the concentrations of copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) in the edible parts of grapefruit and kinnow fruit irrigated with sewage water (SW), tube-well water (TW), and canal water (CW). Preparation of the samples used in the study for metal analysis was carried out via the wet acid digestion method. Atomic absorption spectrometry (AAS) was used for metal determination. According to the results, Cu concentration ranged from 0.152 to 0.754 mg/L in water, 5.254 to 41.659 mg/kg in soil, and 0.128 to 0.864 mg/kg in fruit samples. Zn concentration varied from 0.574 to 2.723 mg/L in water, 17.812 to 112.954 mg/kg in soil, and 2.658 to 42.642 mg/kg in fruit samples. Fe concentration ranged from 0.254 to 1.245 mg/L in water, 10.635 to 48.638 mg/kg in soil, and 1.062 to 7.584 mg/kg in fruit samples. Mn concentration ranged from 0.154 to 0.638 mg/L in water, 51.283 to 183.865 mg/kg in soil, and 0.136 to 1.464 mg/kg in fruit samples. The Pollution Load Index (PLI) indicated that Cu and Mn exceeded a PLI value of one, and Zn had a PLI > 1 only in sewage water-irrigated sites. Bioconcentration Factor (BCF), Enrichment Factor (EF), Daily Intake of Metal (DIM), and Health Risk Index (HRI) values for all metals were within permissible limits, indicating no immediate health risks associated with consuming these fruits. Full article

The present study investigated the applicability of constructed wetlands (CWs) filled with oyster shells (OSs) for removing heavy metals from acid mine drainage (AMD). Lab-scale CWs consisted of columns (ID 12.5 cm, H 50 cm) packed with OSs or limestone, which were left unplanted or planted with cattails. Synthetic and real AMD containing 7.3 mg/L of Zn, 38.0 mg/L of Fe, and other minerals (pH = 4.0) were fed to the CWs (1 L/column) under a hydraulic retention time of 7 days in a sequencing batch mode. The effluent pH values of the CWs reached 6.9–8.3. Results show that OSs with high CaCO₃ contents had higher neutralizing capability for AMD than limestone had. During 7 months of operation, all CWs were highly effective for removing Zn (88.6–99.2%); Fe (98.7–99.7%); and Cd, Cu, Pb, As, and Mn (48.2–98.9%) from both real and synthetic AMD. The mass balance in the CWs indicated accumulation in OSs or limestone as a main pathway for removing heavy metals, representing 44.8–99.3% of all metals, followed by biomass (8.8–29.9%) in the planted CWs. Other processes examined for this study only played a minor role in removing heavy metals. The higher metal treatment performance of OS CWs demonstrated the value of this aquaculture byproduct as a CW substrate. Full article

The current paper is related to the study of the microstructure and texture of two machinable lead-free brass alloys, namely CuZn42 (CW510L) and CuZn38As (CW511L), which were evaluated in the as-drawn and post heat treated condition. Electron backscatter diffraction (EBSD) was employed for the examination of the brass rods’ crystallographic properties in order to correlate the effect of post processing heat treatment on the evolution of phase structure and texture towards the interpretation of dynamic (impact) fracture properties. It is shown that α- and β-phase volume fractions, mean grain size, and grain boundary misorientation are the most influential factors altering the fracture resistance of single- and dual-phase brass alloy rods. The role of grain boundary engineering, through the formation of coincidence site lattice (CSL) boundaries and their evolution during thermomechanical processing, is of major importance for the design of the mechanical behaviour of new eco-friendly machinable brass alloys. Full article

This study demonstrated heavy metal removal from neutral mine drainage of a closed mine in Kyoto prefecture in pilot-scale constructed wetlands (CWs). The CWs filled with loamy soil and limestone were unplanted or planted with cattails. The hydraulic retention time (HRT) in the CWs was shortened gradually from 3.8 days to 1.2 days during 3.5 months of operation. A short HRT of 1.2 days in the CWs was sufficient to achieve the effluent standard for Cd (0.03 mg/L). The unplanted and the cattail-planted CWs reduced the average concentrations of Cd from 0.031 to 0.01 and 0.005 mg/L, Zn from 0.52 to 0.14 and 0.08 mg/L, Cu from 0.07 to 0.04 and 0.03 mg/L, and As from 0.011 to 0.006 and 0.006 mg/L, respectively. Heavy metals were removed mainly by adsorption to the soil in both CWs. The biological concentration factors in cattails were over 2 for Cd, Zn, and Cu. The translocation factors of cattails for all metals were 0.5–0.81. Sulfate-reducing bacteria (SRB) belonging to Deltaproteobacteria were detected only from soil in the planted CW. Although cattails were a minor sink, the plants contributed to metal removal by rhizofiltration and incubation of SRB, possibly producing sulfide precipitates in the rhizosphere. Full article

This paper describes a case study that was carried out on a Sicilian company (Italy) dealing with separate waste collection and recycling of glass. The aims of this study were to evaluate the overall efficiency of a vertical subsurface flow system (VSSFs) constructed wetland (CW) operating for the treatment of first-flush stormwater and the effects of treated wastewater on the morphological and aesthetic characteristics of ornamental pepper and rosemary plants. The system had a total surface area of 46.80 m² and was planted with common reed and giant reed. Wastewater samples were taken from October 2018 to July 2019 at the CW inlet and outlet for chemical-physical and microbiological characterization of the wastewater. Two separate experimental fields of rosemary and ornamental pepper were set up in another Sicilian location. Three sources of irrigation water, two accessions of rosemary and two varieties of ornamental pepper were tested in a split-plot design for a two-factor experiment. The results showed very high organic pollutant removal (BOD₅ 75–83%, COD 65–69%) and a good efficiency of nutrients (TN 60–66%) and trace metals (especially for Cu and Zn) removal. Escherichia coli concentration levels were always lower than 100 CFU 100 mL⁻¹ during the test period. Irrigation water and plant habitus had significant effects on all the morphological and aesthetic characteristics of the plants. For both the crops, plants irrigated with freshwater and treated wastewater had greater growth and showed a better general appearance in comparison with plants irrigated with wastewater. The higher trace metal levels in the wastewater produced adverse effects on plant growth and reduced the visual quality of the plants. Our results suggest the suitability of a VSSFs constructed wetland for the treatment of first-flush stormwater and the reuse of treated wastewater for irrigation purposes, in accordance with legislation requirements concerning wastewater quality. Full article

Heat treatment was performed in order to improve the machinability of three lead-free extruded and drawn brasses, namely CuZn42 (CW510L), CuZn38As (CW511L), and CuZn36 (C27450), based on the concept of microstructural modification. The examined machinability criteria were the following: chip morphology, power consumption, cutting force, and surface roughness. All the above quality characteristics were studied in turning mode in “as received” and “heat treated” conditions for comparison purposes. The selected heat treatment conditions were set for CW510L (775 °C for 60 min), CW511L (850 °C for 120 min), and C27450 (850 °C for 120 min) lead-free brass alloys, according to standard specification and customer requirement criteria. The results are very promising concerning the chip breaking performance, since the heat treatment contributed to the drastic improvement of chip morphology for every studied lead-free brass. Regarding power consumption, heat treatment seems beneficial only for the CW511L brass, where a reduction by 180 W (from 1600 to 1420 W), in relation to the as-received condition, was achieved. Furthermore, heat treatment resulted in a marginal reduction by 10 N and 15 N in cutting forces for CW510L (from 540 to 530 N) and CW511L (from 446 to 431 N), respectively. Finally, surface roughness, expressed in terms of the average roughness value (Ra), seems that it is not affected by heat treatment, as it remains almost at the same order of magnitude. On the contrary, there is a significant improvement of maximum height (Rt) value of CW511L brass by 14.1 μm (from 40.1 to 26.0 μm), after heat treatment process performed at 850 °C for 120 min. Full article

The machinability in turning mode of three lead-free brass alloys, CuZn42 (CW510L), CuZn38As (CW511L) and CuZn36 (C27450) was evaluated in comparison with a reference free-cutting leaded brass CuZn39Pb3 (CW614N), as far as the quality characteristics, i.e., cutting force and surface roughness, were concerned. A design of experiments (DOE) technique, according to the Taguchi L₁₆ orthogonal array (OA) methodology, as well as analysis of variance (ANOVA) were employed in order to identify the critical-to-machinability parameters and to obtain their optimum values for high-performance machining. The experimental design consisted of four factors (cutting speed, depth of cut, feed rate and alloy) with four levels for each factor using the “smaller-the-better” criterion for quality characteristics’ optimization. The data means and signal-to-noise (S/N) responses indicated that the depth of cut and the feed rate were the most influential factors for the cutting force and surface roughness, respectively. The optimized machining parameters for cutting force (34.59 N) and surface roughness (1.22 μm) minimization were determined. Confirmation experiments (cutting force: 39.37 N and surface roughness: 1.71 μm) seem to show that they are in close agreement to the main conclusions, thereby validating the findings of the statistical evaluation performed. Full article

For the treatment of wastewater containing organic pollutants and metals in constructed wetlands (CWs), phytoindicators may help in guiding management practices for plants and optimizing phytoremediation processes. Hairy willow-herb (Epilobium hirsutum L.) is a fast growing species commonly found in European CWs that could constitute a suitable phytoindicator of metal toxicity. E. hirsutum was exposed for 113 days in microcosm CWs, to a metal and metalloid mixture (MPM, containing Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sn, Zn), an organic pollutant mixture (OPM, containing hydrocarbonsC₁₀-C₄₀, phenanthrene, pyrene, anionic detergent LAS) and an organic pollutant and metal and metalloid mixture (OMPM), separately and at concentration levels mimicking levels of industrial effluents. Analyses of metal and As concentrations in biomass, and different biometric and physiological measurements were performed. Results showed that metal uptake patterns were affected by the type of pollutant mixture, resulting in variation of toxicity symptoms in E. hirsutum plants. Some of them appeared to be similar under MPM and OMPM conditions (leaf chlorosis and tip-burning, decrease of green leaf proportion), while others were characteristic of each pollutant mixture (MPM: Decrease of water content, increase of phenol content; OMPM: reduction of limb length, inhibition of vegetative reproduction, increase of chlorophyll content and Nitrogen balance index). Results emphasize the potential of E. hirsutum as a bioindicator species to be used in European CWs treating water with metal, metalloid and organic pollutants. Full article