Catalytic recovery of metals from end-of-life polycrystalline silicon photovoltaic cells: Experimental insights into silver recovery.

A steady increase in end-of-life (EoL) polycrystalline silicon photovoltaic (c-Si PV) panels is necessitating the development of recycling technologies to guarantee sustainable environmental management and a circular economy. Herein, we propose a comprehensive EoL c-Si PV recycling strategy with an emphasis on selective silver (Ag) recovery. Primarily, a combination of physical and thermal treatment led to the isolation of PV cell fraction from the EoL PV module. Thereafter, a less-toxic, sulphuric acid-hydrogen peroxide (1 M H2SO4- H2O2 1% (v/v %)) lixiviant was used for Ag leaching at 70 °C. A novel catalytic process using platinum-embedded activated carbon (Pt/AC) was used with only hydrogen gas and air to recover selectively and concentrate the Ag+ from the synthetic PV cells leachate. Finally, pure metallic silver (Ag > 99.0 %) was obtained by the conventional electrowinning process. This study also proposes an explicit recovery process for Al, Cu, and Si. In addition, the Pt/AC catalytic process could efficiently recover Cu from the PV cells, similar to Ag. Following the complete recovery of Ag and Cu through Pt/AC, there is sufficient scope to isolate other metals like Al and Pb leaving behind crude Si wafers. Hence, the as-proposed recycling and metal recovery process is a newer approach benefiting industrial implementation.

Decomposition of Al13 promoted by salicylic acid under acidic condition: Mechanism study by differential mass spectrometry method and DFT calculation.

Decomposition of the polycation Al13O4(OH)24(H2O)127+ (Al13) promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions, especially in the case of acidic condition that dissolved Al3+ species can be released from the Al-bearing substances. However, the microscopic pathway of synchronous proton-promoted and ligand-promoted decomposition process for Al13 is still in the status of ambiguity. Herein, we applied differential mass spectrometry method and DFT calculation to study the initial detailed process of Al13 decomposition under the presence of proton and salicylic acid (H2Sal). Mass results showed that the mononuclear Al3+-H2Sal complexes dominated the resulting Al species, whereas the monodentate complex Al13HSal6+ was not observed in the spectra. The difference of decomposition levels between the ligand/Al ratio 0.2 and 0.5 cases revealed that proton and ligand performed synergistic effect in initial Al13 decomposition process, and the proton transfer determined the ring closure efficiency. The ring closure reaction is the prerequisite for the collapse of Al13 structure and detachment of the mononuclear complex. DFT calculations reveal that hydrogen bond plays an important role in inducing the formation of chelated complex accompanying proton transfer. Attachment of protons at the bridging OH- can elongate and weaken the critical bond between targeted Al3+ and µ4-O2- resulting from delocalization of electron pairs in the oxygen atom. These results demonstrate the detailed mechanism of Al13 composition promoted by ligand and proton, and provide significant understanding for further application and control of Al13.

Post COVID-19 vaccination side effects and associated factors among vaccinated health care providers in Oromia region, Ethiopia in 2021.

BACKGROUND: Severe Acute Respiratory Syndrome (SARS COV-2) known as COVID-19 since its outbreak in 2019, more than 375 and 5.6 million were infected and dead, respectively. Its influence in all disciplines stimulated different industries to work day to night relentlessly to develop safe and effective vaccines to reduce the catastrophic effect of the disease. With the increasing number of people globally who have been vaccinated, the reports on possible adverse events have grown and gained great public attention. This study aims to determine post-COVID-19 vaccination adverse effects and associated factors among vaccinated Health care providers in the Oromia region, Ethiopia in 2021. METHODS: A cross-sectional study was conducted among 912 health care workers working in government hospitals in the central Oromia region from November 20 to December 15/2021. Respondents absent from work due to different reasons were excluded during the interview. The outcome variable was COVID-19 side effects (response as Yes/No). A descriptive analysis displayed findings in the form of the frequencies and percentages, and logistic regression was employed to see the association of different variables with side effects experienced. RESULT: Overall, 92.1% of the participants experienced side effects either in 1st or 2nd doses of post-COVID-19 vaccination; 84.0% and (71.5%) of participants experienced at least one side effect in the 1st and 2nd dose of the vaccines, respectively. COVID-19 infection preventive protocols like keeping distance, hand wash using soap, wearing mask and using sanitizer were decreased post vaccination. About 74.3% of the respondents were worried about the adverse effects of the COVID-19 vaccine they received. The majority (80.2%) of the respondent felt fear while receiving the vaccine and 22.5% of the respondents suspect the effectiveness of the vaccine they took. About 14.8% of the vaccinated Health workers were infected by COVID-19 post-vaccination. Engaging in moderate physical activity and feeling fear when vaccinated were the independent factors associated with reported side effects of post-COVID-19 vaccination using multiple logistic regression. Respondents who did not engage in physical activity were 7.54 fold more likely to develop post-COVID-19 vaccination side effects compared to those who involved at least moderate-intensity physical activity[AOR = 7.54, 95% CI;2.46,23.12]. The odds of experiencing side effects among the respondents who felt fear when vaccinated were 10.73 times compared not felt fear (AOR = 10.73, 95% CI; 2.47,46.64), and similarly, those who felt little fear were 4.28 times more likely to experience side effects(AOR = 4.28, 95% CI; 1.28, 14.39). CONCLUSION: Significant numbers of the respondents experienced side effects post COVID-19 vaccination. It is recommended to provide pre-awareness about the side effects to reduce observed anxiety related to the vaccine. It is also important to plan monitoring and evaluation of the post-vaccine effect using standard longitudinal study designs to measure the effects directly.

Concentrations, bioaccumulation, and health risk assessments of heavy metals in fishes from Nigeria's freshwater: a general overview.

Heavy metals (HMs) have attracted global attention due to their toxicity, persistence, and accumulation in aquatic fish in the polluted water environment. The consumption of these fishes exposed humans to a higher risk of non-carcinogenic and carcinogenic risks. In this study, we provided a critical overview of the potential sources and concentration of HMs in Nigeria's freshwater. Furthermore, we reported their pollution level in widely eaten fish species in the country. Our findings show that effluent from anthropogenic and industrial activities is one of the major sources HMs in the country. The mean concentration of Zn (9.02 mg/L), As (7.25 mg/L), Cu (4.35 mg/L), Fe (1.77 mg/L), and Pb (1.46 mg/L) in Nigeria's freshwaters were found to be high than Nigerian Standard for Drinking Water Quality permissible limit. This study demonstrated considerable health risks associated HMs via dietary consumption of different fishes from polluted waters. Therefore, we recommended an urgent need for effective management HMs in water bodies in order to protect the lives of people living in the country.

Identification of rainy season nitrogen export controls in a semi-arid mountainous watershed, North China.

A comprehensive understanding of the nutrient export process and export controls is demanded effective pollution mitigation in fragile riverine ecosystems. In this study, behaviors of the full range of nitrogen (N) under stormflow (5-events) and baseflow (2-events; before and after the rainy season, multiple sites) were assessed to explore N export controlling mechanisms according to the identified main components causing the changes in N exports, N transport pathways, seasonal trends, and nutrient supply watershed regions through the 2020 rainy season in a semi-arid mountainous watershed, northern China. Results showed increments in riverine dissolved organic-N (DON) and particulate-N (PN) loadings as the leading cause of N flux and composition changes through the rainy season, although nitrate-N (NO3-N) contributed 69.6% of total-N (TN). Storm runoff generated 3-fold and 4-fold average increments in DON and PN fluxes. DON and PN shared 1-66% (18.1%) and 1-44% (9.7%) of TN through storms, registered consistency in behavior, mainly originated from near-stream soil, and were primarily transported by shallower subsurface flow. Our results broaden the understanding of PN delivery in catchment wetting-up periods by highlighting the decoupling of primary origins/transport pathways of PN from sediments. Results suggested hydrological functioning parallel to the catchment wetting-up as the principal governor of storm N evolution; soil moisture levels build up in the early rainy season, soil water runoff dominance during peak discharge fluctuations, groundwater runoff dominance at the end of the rainy season. Cumulative rainfall and antecedent soil moisture exerted more significant control over storm N exports than individual rainfall features. The assessment of N behaviors through river network disclosed watershed regions responsible for excessive N delivery and influences of unsustainable agriculture, sewage treatment work, and damming on natural riverine N fluxes. These findings could be useful references for the formulation of water pollution control strategies in the future.

Knowledge, Attitude, and Practice (KAP) toward Cervical Cancer Screening among Adama Science and Technology University Female Students, Ethiopia.

BACKGROUND: Cervical cancer is a complication of Human Papillomavirus (HPV) infection is the second most common cancer in women worldwide. Eighty percent of the cases occur in low-resource countries. According to the 2009 World Health Organization report, the age-adjusted incidence rate of cervical cancer in Ethiopia was 35.9 per 100,000 patients with 7619 annual number of new cases and 60-81 deaths every year. The study is aimed at assessing the level of knowledge, attitude, and practice concerning cervical cancer among female students at Adama Science and Technology University. Methodology. An institutional based cross-sectional study was conducted among 667Adama Science and Technology University female students. A simple random sampling method was used to select the respondents. Structured self-administered questionnaire was used for data collection. RESULTS: About 404 (60.6%) of the participants heard about cervical cancer, 478 (71.7%) had positive attitude towards cervical cancer screening, and only 15 (2.2%) participants were screened for cervical cancer. Lack of information about cervical cancer was the most reported reason for not attending to cervical cancer screening. Conclusion and Recommendation. The study showed that there was low knowledge on cervical cancer and screening for premalignant lesion among women. There is a need to promote and encourage women to early cervical cancer screening at precancerous stage by informing their susceptibility to cervical cancer.

Effects and behaviors of Microcystis aeruginosa in defluorination by two Al-based coagulants, AlCl3 and Al13.

The complexity of natural water made it difficult to remove fluoride. Based on the environmental problems found in the investigation, the fluoride removal research in the water containing algal cells was carried out. In this study, AlCl3 and [AlO4Al12(OH)24(H2O)12]7+ (Al13) were used to remove fluoride. Additionally, the role of aluminum speciation in fluoride removal and the effect of Microcystis aeruginosa on the fluoride removal by different aluminum species coagulants were elucidated. The results showed that AlCl3 mainly removed fluoride by physical interactions, surface adsorption and enmeshment. When algal cells were added to the system, the fluoride removal rate increased from 22.75 % to 72.99 % at a dosage of 40.0 mg/L. This was because algal cells greatly increased the distribution of Al(OH)3 in the flocs. In particular, the specific surface area of the flocs containing algal cells reached 160.77 m2/g, which allowed more fluoride to be adsorbed. However, excessive Al3+ led to serious damage to algal cells and release of intracellular organic matter (IOM), worsening the effect of defluoridation. F- and Al3+ formed AlF2+ and AlF2+ via complexation in water. These compounds were not conducive to defluoridation. Al13 removed fluorine mainly through ion exchange, substitution and hydrogen bonding. Algal cells had an inhibitory effect on defluorination, which was observed in the process of coagulation by different Al dosages. Al13 achieved agglomeration of algal cells and generated small and dense flocs through charge neutralization and electrostatic patch mechanism. Once Al13 combined with algal cells and algae organic matter (AOM), the reaction between Al13 and fluoride would be weakened. Al13 not only maintained the defluoridation performance, but also did not damage the integrity of algal cells, even at high dosages.

Deprotonation and aggregation of Al13 under alkaline titration: A simulating study related to coagulation process.

Unraveling the transformation of coagulants and their interaction with contaminants at the micro-level is vital to advancing our understanding of the coagulation mechanism. To the best of our knowledge, the coagulation effectiveness of [AlO4Al12(OH)24(H2O)12]7+ (Al13), regarded as the dominant species in polyaluminum chloride (PACl), is highly related to its aggregation characteristic, but the detailed process of Al13 aggregation in coagulation time scale was not well studies. Here we systematically studied the deprotonation and aggregation processes of Al13 by alkaline titration to simulate the reaction in coagulation case. By reacting with OH-, Al13 can continuously lose protons regardless of pH until its positive charge was well neutralized. The initial Al13 aggregates (Al13agg) appeared at B of 2.70 and large Al13agg was generated by coalescence of small initial Al13agg. Most Al13 polycations kept their main structure unchanged during aggregation and part was decomposed into monomers or oligomers. Density functional theory (DFT) results reveal that Al13 becomes unstable after deprotonation, but the aggregation of Al13 bridged by Al monomers can stabilize the polycations. Al13 needs to be hydrolyzed before interacting with colloidal particles, but particles can promote the aggregation of Al13 by weakening the repulsion force between the polymers. Strong and compact flocs can be generated induced by in-situ aggregation of Al13 in neutral and alkaline conditions. This study can provide a deep understanding about the role of Al13agg in removing particles and instruct the development of new efficient coagulants against the various water qualities.

Advances in micro interfacial phenomena of adsorptive micellar flocculation: Principles and application for water treatment.

Among various aqua remediation technologies, separation aims at cleaning pollutants by isolating them despite their destruction; solutes can also be recovered after the process. Adsorptive micellar flocculation (AMF) has been known as an important surfactant-based technique to separate poorly water-soluble hazardous pollutants from aqua media as an efficient and energy-intensive replacement for other surfactant-based techniques, as such AMF should be known. AMF is based on the partitioning of solutes gradient from bulk solution into the nanosized smart anionic surfactant micelle followed by flocculation. However, unlike coagulation/flocculation or adsorption, AMF is not viable for the production of drinking water in water utilities due to the loss of surfactant monomers. Unfortunately, it can be used as a reservoir or for the recycling/recovery of organic pollutants (intermediates) (ions, organics/bioactive, dyes, etc.), even at high concentrations. The performance of AMF depends on various parameters, and this review briefly summarizes the existing researches on different pollutants removal by AMF and material recovery/recycling. This includes operating condition factors (surfactants, flocculants, surfactant-flocculant or surfactant-pollutant concentration ratio, and water conditions chemistry). Because varieties of micro interfacial phenomena other than physical interactions occur in a versatile micellar environment in the AMF process, emphases are given to adsorptive oxidation, micellar catalysis, selectivity. Furthermore, for the first time, this review gives an overview of understanding the state-of-the-art multifunctional nano amphiphile-based AMF that behaves mimetic to aquatic organisms in the process of pollutant removal. The efficiency of AMF, including recycling concentrated solution without noticeable deterioration, as an auxiliary resource/income for the next cycle, signifies economic viability, versatility, and manifold applications in aqua remediation. Significance, ways to achieve enhanced process efficiency, as well as challenges and future opportunities in wastewater treatment, are also highlighted.

Formation of Al30 aggregates and its correlation to the coagulation effect.

Al30 is the polycation with the highest degree of polymerization and surface charge in the currently known structural aluminum species. It shows excellent coagulation performance in water treatment process, and has the characteristics of wide application range of pH and dosage. pH value is one of the most important factors affecting the aggregation and coagulation process of Al30, but the influence of Al30 aggregation reaction on its coagulation effect is still unclear. Therefore, this article reports the deprotonation and aggregation reaction of Al30 by adjusting the basicity (B) of the solution, particularly to further understand the coagulation mechanism of Al30 under different conditions. The results showed that in the base titration process, when B < 2.86 in 0.01 M Al30 solution as AlT (the concentration of total Al), deprotonation and preliminary aggregation mainly occurred; when B > 2.86, the size of Al30 aggregates (Al30agg) increased rapidly, forming gels and gradually transforming into Al(OH)3. In this process, in addition to the reduction of electrostatic repulsion induced by Al30 deprotonation, the oligomers generated by the partial dissociation of Al30 also play the role of bridging-connection. Under the experimental titration conditions, the Al30agg always maintained a positive zeta potential. In addition, Al30 can deprotonate and aggregate at lower pH, which is an important reason for its unique coagulation characteristics. The larger structure size of Al30 also made it easy to form branched aggregates, so that it can play an effective role in a wider dosage range without destabilization of colloids. This study gives an insight in the advancement of coagulants and promotes the industrial application and commercialization of functional coagulants based on polyaluminum.

Optimized pre-treatment of high strength food waste digestate by high content aluminum-nanocluster based magnetic coagulation.

Coagulation-based pre-treatment efficiency of high strength digestate of food waste (HSDFW) anaerobic digestion is negated by organic ligand-catalyzed decomposition of coagulants. In this study, an efficient HSDFW pre-treatment method, magnetic seeds (MS) coagulation, was employed by using highly stable Keggin Al30 nanocluster (PAC30), MS and polyacrylamide (PAM), and its operation was optimized by evaluating the performance of removing turbidity, total suspended solids (TSS), chemical oxygen demand (COD), and total phosphorous (TP) phosphate. Results showed that at the optimum dosage of 4.82 g/L, PAC30 demonstrated excellent removals as high as 98.93% ± 0.1% of turbidity, 98.04% ± 0.1% of TSS, 58.28% ± 0.3% of total COD, 99.98% ± 0.01% of TP and 99.50% ± 0.01% of dissolved phosphate, respectively. Apparent molecular weight (AMW) and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy analyses demonstrated more efficient removal of dissolved organic matter (DOM), particularly non-biodegradable and hydrophobic components by PAC30 than commercial coagulant. The sedimentation was much improved from 40 min by coagulation/flocculation to about 5 min settling by MS coagulation. The PAC30 based magnetic coagulation (MC) presents theoretical guidance on a cost-effective and much less footprint pre-treatment alternative for high strength wastewater.

Comparison of an integrated short-cut biological nitrogen removal process with magnetic coagulation treating swine wastewater and food waste digestate.

An integration of two processes, magnetic coagulation (MC) and short-cut biological nitrogen removal (SBNR), coupled with a sequencing batch membrane bioreactor (SMBR) controlled by an automatic real-time control strategy (RTC), was developed to treat different characteristics of high strength wastewater. The treatment efficiency and microbial community-diversity of the proposed method was evaluated and investigated using swine wastewater and food waste (FW) digestate. The MC showed high removal of TSS (89.1 ± 1.5%, 92.21 ± 1.8%), turbidity (90.58 ± 2.1%, 95.1 ± 2.1%), TP (88.5 ± 1.9%, 92.1 ± 1.5%), phosphate (87.76 ± 1.6%, 91.22 ± 1.5%), and SMBR achieved stable and excellent removal of COD (96.05 ± 0.2%, 97.39 ± 0.2%), TN (97.30 ± 0.3%, 97.44 ± 0.3%) andNH4+-N (99.07 ± 0.2%, 98.54 ± 0.2%) for swine wastewater and FW digestate, respectively. The effluent COD andNH4+-N concentrations were found to meet their discharge standards. The microbial community comparison showed similar diversity and richness, and genus Diaphorobacter and Thaurea were dominant in denitritation, and Nitrosomonas was dominant in nitritation treating both swine wastewater and FW digestate.

Design and application of metal-organic frameworks and derivatives as heterogeneous Fenton-like catalysts for organic wastewater treatment: A review.

Advanced oxidation process (AOP), with a high oxidation efficiency, fast reaction speed (relatively no secondary pollution), has become one of the core technologies of industrial wastewater and advanced drinking water treatment. Heterogeneous Fenton-like oxidation process (HFOP) is a kind of AOP, which developed rapidly in recent years in such a way to overcome the disadvantages of traditional Fenton reaction. Metal-organic frameworks (MOFs) and their derivatives become essential heterogeneous catalysts for organics mineralization due to the large specific surface area, abundant active sites, and ease of structural regulation. However, the knowledge gap on the mechanism and the fate of heterogeneous catalyst species during organics degradation activities by MOFs presents considerable impediments, particularly for a wide application and scaling up the process. This work has the potential to provide guidance and ideas for researchers and engineers in the fields of environmental remediation, environmental catalysis and functional materials. This review focuses on clarifying the critical mechanism of •OH production from MOFs and derivatives as well as its action on the organic's degradation process. The recent developments in MOF based HFOP are compared, and more attention is paid for the following aspects in this review: (1) classifies systematically progressive modification methods of MOFs by chemical and physical treatments; (2) analyzes the fate of catalytic species during treating organic wastewater; (3) proposes design ideas and principles for improving the performance of MOFs catalysts; (4) discusses the main factors influencing the catalytic properties and practical application; (5) summarizes the possible research challenges and directions for MOFs and their derivatives as catalysts applied to wastewater treatment in the future.

Removal of phenolic contaminants from water by in situ coated surfactant on Keggin-aluminum nanocluster and biodegradation.

Recent water treatment plants require multi-process techniques to remove contaminants from aqua media. In this study, we investigate the novel, in situ coated sodium dodecylsulphate (SDS), on kegging Al30 nanocluster as a single water treatment alternative for the removal of phenolic contaminants and suspension. FTIR, TEM-EDX and Zeta potential analysis characterized the nanocluster decoration. The resulting property was examined by emission (λ-max) of the molecular probe, the online aggregate image of fluorescence microscopy, and mixing isochrone, fat-soluble dye solubilization. The coated media was examined as nearly resembling the hydrophobicity of 1-octanol. The elemental line scanning and mapping showed different morphologies of floc depending on the SDS concentration. The material was found to follow Brownian motion to enmesh suspended particles like a ladder, and served as entrapper for small organic contaminants by the sorbed SDS aggregate, based on their log KO/W. About 85% and ≥95% removal archived for contaminants with the least and highest KO/W value, respectively. The residual solutes in the supernatant were well decomposed by using a bacterial agent. One-step removal (less footprint) and ease of operation make this approach an environmentally compatible and cost-effective alternative for the large-scale treatment process.