Fly ash from waste incineration is growing rapidly and has become a global problem. Landfill is the main treatment method, but the release behavior of ultra-alkaline fly ash needs further study. In ...this study, the release pattern of heavy metals from fly ash, the long-term risk after seepage, and the main control mechanisms were explored by indoor simulation experiments and process simulation modeling. The results show that carbonation is the main control mechanism for the release rate of heavy metals from super-alkaline fly ash, and the release rate is slow at the initial stage, but the release concentration of Zn and Pb may increase tens of times with the continuous reaction between the acidic substances in the leachate and the alkaline substances in the fly ash. The heavy metals released into the leachate can cause the concentration of Zn, Cd and Pb in the groundwater to exceed the standard by 39.50, 6.70 and 5.99 times due to seepage. Furnace type is the key controlling factor for background concentrations of heavy metals in ultra-alkaline fly ash, and the exposure concentrations of Cu, Cd, Zn, and Pb in ultra-alkaline fly ash from grate furnaces as well as the GT1 facility are 4.19, 4.19, 4.14, and 37.5 times greater than those of fluidized beds, respectively, with a higher risk of long-term landfill. Regionally, the regional occupancy rate of heavy metal concentrations indicated that the risk of adequate rainfall was high in the southeastern coastal region, which was five times higher than that in the inland northwest. Therefore, the long-term dynamics and risk evolution of Zn, Cd, and Pb in the groundwater around MSWLs in the coastal area should be paid attention to after the landfilling of ultra-alkaline fly ash in order to ensure the safety of the shallow groundwater environment after landfilling.
Fly ash from waste incineration is growing rapidly and has become a global problem. Landfill is the main treatment method, but the release behavior of ultra-alkaline fly ash needs further study. In this study, the release pattern of heavy metals from fly ash, the long-term risk after seepage, and the main control mechanisms were explored by indoor simulation experiments and process simulation modeling. The results show that carbonation is the main control mechanism for the release rate of heavy metals from super-alkaline fly ash, and the release rate is slow at the initial stage, but the release concentration of Zn and Pb may increase tens of times with the continuous reaction between the acidic substances in the leachate and the alkaline substances in the fly ash. The heavy metals released into the leachate can cause the concentration of Zn, Cd and Pb in the groundwater to exceed the standard by 39.50, 6.70 and 5.99 times due to seepage. Furnace type is the key controlling factor for background concentrations of heavy metals in ultra-alkaline fly ash, and the exposure concentrations of Cu, Cd, Zn, and Pb in ultra-alkaline fly ash from grate furnaces as well as the GT1 facility are 4.19, 4.19, 4.14, and 37.5 times greater than those of fluidized beds, respectively, with a higher risk of long-term landfill. Regionally, the regional occupancy rate of heavy metal concentrations indicated that the risk of adequate rainfall was high in the southeastern coastal region, which was five times higher than that in the inland northwest. Therefore, the long-term dynamics and risk evolution of Zn, Cd, and Pb in the groundwater around MSWLs in the coastal area should be paid attention to after the landfilling of ultra-alkaline fly ash in order to ensure the safety of the shallow groundwater environment after landfilling. Display omitted
•The long-term landfill risk of SAFA was assessed experimentally and by modeling.•The long-term risk of SAFA was found to be much higher than that of ordinary fly ash.•Furnace type was the main influencing factor for heavy metal concentrations in SAFA.
•Temporal release of Zn and K from a burning hyperaccumulator pellet was measured.•The release characteristics of different chemical groups of Zn and K were studied.•Differences in the release ...behavior between Zn and K were compared.•Inhibition effects of four additives on Zn and K release were investigated.•A Ca-Al-Zn transformation mechanism promoting Zn retention efficiency was proposed.
Hyperaccumulators, as a special plant, are capable of absorbing heavy metals from contaminated soil. Thermal utilization of hyperaccumulator biomass is therefore more challenging, due to the requirement of avoiding secondary pollution of heavy metals. To investigate dynamic alkali and heavy metal release during hyperaccumulator combustion, we used multi-point laser-induced breakdown spectroscopy (LIBS) to measure zinc (Zn) and potassium (K) release from a burning Sedum alfredii pellet. The results show that 24.2% of Zn and 61.5% of K are released during the Sedum alfredii combustion through two stages, i.e., (1) devolatilization and (2) char and ash reactions. The latter is the primary release stage, accounting for 69.8% and 77.6% of the total released Zn and K, respectively. The release characteristics of different chemical groups of Zn and K are then studied by performing LIBS on Sedum alfredii treated with solvent fractionation in three sequential steps. NH4Ac-soluble Zn and H2O-soluble K are found to be the primary released Zn and K groups, respectively. Furthermore, inhibition effects of two synthetic additives, silica (SiO2) and alumina (Al2O3), and two natural mineral additives, kaolin, and mica, on Zn and K release have been investigated. All the four additives achieve an inhibition efficiency higher than 55% on K release through aluminosilicate reactions and physical absorption. However, the performance of these additives on Zn retention is not as good as for K. The highest Zn retention efficiency is 37.0% achieved by Al2O3, which can be explained by a Ca-Al-Zn transformation mechanism converting volatile Zn to Ca3Al4ZnO10.
Pulsed electric field (PEF) technology is an alternative to traditional food processing because this application can ensure good product quality and energy use efficiency. In PEF applications, the ...functional compounds extracted from food products can be enhanced, and the microorganisms contaminating the food products during processing can be inactivated. These properties are considered advantageous by alcoholic beverage producers. In this review, studies on the PEF treatment of wine, beer, and rice wine are summarized. The PEF technology is used in the pretreatment in grape wine and control of microbial growth in grape wine, beer, and rice wine. In grape wines, the PEF pretreatment can increase phenolic compound and anthocyanin contents and can enhance color intensity; this pretreatment slightly influences the organoleptic characteristics of samples. The PEF technology is also an effective tool to sterilize grape wine, beer, and rice wine. With this application, the quality of these three alcoholic beverages can be ensured because the PEF technology can be applied in the absence of heat. In addition, the main negative effect of PEF technology is discussed as well.
•PEF used as pretreatment and sterilization treatments in wines were introduced.•Common effects of PEF on the quality of alcoholic beverages were summarized.•Effects of PEF on inactivation of microorganism suspended in wines were introduced.•Negative effects of PEF were included, namely metal release of electrode corrosion.
•Presence of protons and ligands in soil increased the bioavailability of Pb and Cu.•Biochar reduced Pb and Cu release rates to 99.5%.•Electrostatic attraction and complexation to biochar could ...immobilize Pb and Cu.
Display omitted
Presence of organic and inorganic acids influences the release rates of trace metals (TMs) bound in contaminated soil systems. This study aimed to investigate the influence of bioenergy waste biochar, derived from Gliricidia sepium (GBC), on the proton and ligand-induced bioavailability of Pb and Cu in a shooting range soil (17,066mg Pb and 1134mg Cu per kg soil) in the presence of inorganic (sulfuric, nitric, and hydrochloric) and organic acids (acetic, citric, and oxalic). Release rates of Pb and Cu in the shooting range soil were determined under different acid concentrations (0.05, 0.1, 0.5, 1, 5, and 10mM) and in the presence/absence of GBC (10% by weight of soil). The dissolution rates of Pb and Cu increased with increasing acid concentrations. Lead was preferentially released (2.79×10−13 to 8.86×10−13molm−2s−1) than Cu (1.07×10−13 to 1.02×10−13molm−2s−1) which could be due to the excessive Pb concentrations in soil. However, the addition of GBC to soil reduced Pb and Cu dissolution rates to a greater extent of 10.0 to 99.5% and 15.6 to 99.5%, respectively, under various acid concentrations. The increased pH in the medium and different adsorption mechanisms, including electrostatic attractions, surface diffusion, ion exchange, precipitation, and complexation could immobilize Pb and Cu released by the proton and ligands in GBC amended soil. Overall, GBC could be utilized as an effective soil amendment to immobilize Pb and Cu in shooting range soil even under the influence of soil acidity.
Despite being corrosion-resistant, plastic potable water pipes might accumulate heavy metals on their surface if they convey metal-contaminated tap water. This study examined the influence of water ...pH and flow conditions on lead (Pb) release from new and biofilm-laden potable water pipes to provide insights regarding decontamination. For this purpose, biofilms were grown onto new crosslinked polyethylene (PEX-A), high-density polyethylene (HDPE), and copper pipes for three months. Lead was then deposited onto the new and biofilm-laden pipes through 5 d exposure experiments under flow conditions. After that, lead release experiments were conducted by exposing the lead-accumulated pipes to lead-free synthetic tap water for 5 d, under both stagnant and water flow conditions. The metal accumulation study showed no significant difference in lead uptake by new pipes and their biofilm-laden counterparts under flow conditions. This could be attributed to the detachment of biofilms that have accumulated lead as water flows through the pipes. Water flow conditions significantly influenced the lead release from new and biofilm-laden water pipes. A lower water pH of 5.0 increased the release of lead from plastic pipes into the contact water, compared to pH 6.0 and 7.8. The greatest percentage of lead was released from biofilm-laden HDPE pipes (5.3%, 120 h) compared to biofilm-laden copper pipes (3.9%, 6 h) and PEX-A (3.7%, 120 h) and after exposure to lead-free synthetic tap water at pH 5.0, under stagnant conditions. On the other hand, under water flow conditions, the greatest lead release was found for new PEX-A pipes (4.4%, 120 h), new HDPE pipes (2.7%, 120 h), and biofilm-laden copper pipes (3.7%, 2 h).
Display omitted
•Pb depositions on new and biofilm-laden water pipes were not different under flow conditions.•The lower pH promoted lead release from new plastic and copper potable water pipes.•Biofilm-laden plastic pipes released more Pb than new pipes under stagnant conditions.
Ceramic water filters (CWFs) are decentralized water treatment technologies commonly used in resource-restricted geographies. Inclusion of silver nanoparticles (AgNP) assists with disinfection but ...can substantially increase costs. This research investigates AgNP supplementation with zinc oxide (ZnO) as a low-cost bactericide alternative. CWF disks were impregnated with varying AgNP and/or ZnO concentrations and challenged against Escherichia coli. Effluent bacteria were enumerated and monitored over 72 h while eluted metal concentrations were measured and scaled according to surface area to establish ‘pot-equivalent’ estimates (0–50 ppb Ag and 0–1200 ppb Zn). Ag addition correlated to subsequent measured release values, though Zn impregnation did not. Background Zn was thus evidently present. Meanwhile, the eluted metal concentration related to disinfection: a CWF with a pot-equivalent elution estimate of 2 ppb Ag and 156 ppb Zn achieved a Log Removal Value (LRV) of 2.0 after 60 min of filtration and 1.9 after 24 h of storage while a CWF with a pot-equivalent elution estimate of 20 ppb Ag and 376 ppb Zn achieved LRVs of 3.1 and 4.5 after the same filtration and storage times, respectively. Clay elemental composition may therefore impact filter performance more than previously considered This trend was further confirmed by batch experiments with Ag and Zn in concentrations of 0–20 ppb Ag and 0–800 ppb Zn, respectively: bacterial regrowth was only observed when Ag and Zn were each below 5 ppb and 160 ppb while 1 ppb Ag and 800 ppb Zn maintained complete disinfection for 72 h. Increased Zn concentrations thus reduced Ag required to maintain disinfection over time. Overall, it is recommended to include Zn with Ag for CWF to improve short-term and long-term disinfection efficacy and associated water safety.
Display omitted
•Ag and Zn synergistically disinfect E. coli in ppb-level concentrations.•Bacteria regrew over 72 h if <10 ppb Ag and 160 ppb Zn present.•Addition of Zn to Ag impregnated ceramic filters improved disinfection.•Background Zinc in local clay may elute and contribute to disinfection.•Filtration and disinfection together improved water safety.
Sunscreens contain ZnO particles used as a UV filter cause adverse effects in the marine environment through the release of this metal into seawater and its bioaccumulation in organisms. A ...mathematical model using sunscreen colloidal residues, seawater and R. philippinarum clams as differentiated compartments, is proposed in order to interpret both the kinetic pattern and the bioaccumulation of Zn in clams. Two kinetic laboratory experiments were conducted, both with and without clams exposed to sunscreen concentrations from 0 to 200 mg L−1. Both the lowest value of uptake rate coefficient obtained when 5 mg L−1 of sunscreen is added (0.00688 L g−1 d−1) and the highest obtained at sunscreen addition of 100 mg L−1 (0.0670 L g−1 d−1), predict a lower bioavailability of Zn in a complex medium such as the seawater-sunscreen mixtures, in comparison to those studied in the literature. The efflux rate coefficient from clams to seawater increased from 0 to 0.162 d−1 with the sunscreen concentrations. The estimated value of the inlet rate coefficient at all studied concentrations indicates that there is a negligible colloidal Zn uptake rate by clams, probably due to the great stability of the organic colloidal residue. An equilibrium shift to higher values of Zn in water is predicted due to the bioconcentration of Zn in clams. The kinetic model proposed with no constant Zn (aq) concentrations may contribute to a more realistic prediction of the bioaccumulation of Zn from sunscreens in clams.
Display omitted
•Kinetic model of bioconcentration in clams under varying Zn concentrations•Sunscreen colloidal residues, seawater and clams as three model compartments•The model predicts sharp bioaccumulation rates at sunscreen additions up to 200 mg L−1•Obtained model parameters contribute to ecotoxicological research
The ITER Neutral Beam Test Facility (NBTF) is hosted in Padua and includes two experiments: MITICA, the 1 MeV full-scale prototype of the ITER HNB injector, and SPIDER, the 100 keV full-size ITER ...Radio Frequency (RF) negative ion source. SPIDER and MITICA experiments are actively cooled by Ultrapure Water (UPW) to electrically insulate in-vessel components that are biased to high voltage levels. Water conductivity is an important monitored parameter to ensure components' insulation by limiting the leakage current of active cooled equipment. A very low conductivity water is especially important in MITICA, where components need to operate up to 1 MVdc, an insulation level beyond the actual industrial standard. Careful selection of suitable materials for any in-vessel (vacuum insulation) and out-vessel component (air insulation) is of utmost importance, as their interaction with water and different environment may affect their chemical and mechanical properties. Additionally, materials selection can severely influence water chemical characteristics: cooling circuits are made of metals (copper, aluminium, steel) and insulating materials (plastic, rubber) when connecting parts at different electric potentials.
During the first years of cooling plant exploitation, it was shown that water degrades more quickly than estimated by design. The Primary Circuits (PCs) that showed the most severe water degradation during operation are SPIDER and MITICA power supply ones, respectively called PC01 and PC08. This paper describes the results of specific experimental tests performed on MITICA PC08 to evaluate possible causes of water degradation and detect sources of contaminants that might compromise future experimental campaigns. The cooling circuit was subdivided in different sections and water circulation tests were performed at constant temperature and flowrate. Water samples were collected and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses were performed to quantify the type and amount of metals released. Moreover, components samples collected along their cooling circuits were characterized by Scanning Electron Microscope (SEM) technique to detect undesired contaminants and immersed in UPW to study their corrosion behaviour using metal release tests.
Trace heavy metals accumulated in iron corrosion scales within a drinking water distribution system (DWDS) could potentially be released to bulk water and consequently deteriorate the tap water ...quality. The objective of this study was to identify and evaluate the release of trace heavy metals in DWDS under changing source water conditions. Experimental pipe loops with different iron corrosion scales were set up to simulate the actual DWDS. The effects of sulfate levels on heavy metal release were systemically investigated. Heavy metal releases of Mn, Ni, Cu, Pb, Cr and As could be rapidly triggered by sulfate addition but the releases slowly decreased over time. Heavy metal release was more severe in pipes transporting groundwater (GW) than in pipes transporting surface water (SW). There were strong positive correlations (R2 > 0.8) between the releases of Fe and Mn, Fe and Ni, Fe and Cu, and Fe and Pb. When switching to higher sulfate water, iron corrosion scales in all pipe loops tended to be more stable (especially in pipes transporting GW), with a larger proportion of stable constituents (mainly Fe3O4) and fewer unstable compounds (β-FeOOH, γ-FeOOH, FeCO3 and amorphous iron oxides). The main functional iron reducing bacteria (IRB) communities were favorable for the formation of Fe3O4. The transformation of corrosion scales and the growth of sulfate reducing bacteria (SRB) accounted for the gradually reduced heavy metal release with time. The higher metal release in pipes transporting GW could be due to increased Fe6(OH)12CO3 content under higher sulfate concentrations.
Display omitted
•Sulfate could trigger heavy metal release from iron corrosion scales.•Strong correlations exist between the releases of total iron and heavy metals.•Heavy metals release decrease slowly over time after sudden increase by sulfate.•Corrosion scale stabilization and SRB growth inhibit heavy metals release.
PDF