Simultaneous determination of silver and other heavy metals in aquatic environment receiving wastewater from industrial area, applying an enrichment method

Fluorescence sensing and adsorption kinetics of Gd-doped AgInS2 I-III-VI quantum dots - A case study of Ag+ ions interactions

The poor fluorescence properties of magneto-fluorescent paramagnetic-ion (Gd, Mn, or Co) doped I-III-VI quantum dots (QDs) at higher paramagnetic-ion doping concentrations have limited their use in magnetic-driven water-based applications. This work presents, for the first time, the use of stable magneto-fluorescent Gd-doped AgInS2 QDs at high Gd mole ratios of 16, 20, and 30 for the fluorescence detection and adsorption of Ag+ ions in water environments. The effect of pH, initial concentration, contact time, and adsorbent dosage were systematically evaluated. The AgInS2 QDs with the least Gd mole ratio (16) exhibited the best fluorescence characteristics (LOD = 0.88, R2 = 0.9549) while all materials showed good adsorption properties under optimized conditions (pH of 2, initial concentration of 30 ppm, contact time of 10 min and adsorbent dosage of 0.02 g) and a pseudo 2nd order reaction was followed. The adsorption mechanism was proposed to be a combination of ion-exchange, electrostatic interaction, complexation, and diffusion processes. Application in environmental wastewater samples revealed complete removal of Ag + ions alongside Ti2+ Pb2+, Ni2+, Cr3+, and Zn2+ ions.

A fungal functionalized magnetized solid phase extractor for preconcentrations of Pb(II), Mn(II), and Co(II) from real samples

Due to increasing industrialization and overpopulation, the amount of toxic metals is increasing in the environment, including air, soil, water, and food. Solid phase extraction is an efficient and ideal technique to preconcentrate the toxic metals before their measurements by analytical instruments. Russula brevipes was immobilized on γ-Fe₂O₃ magnetic nanoparticles and employed as a SPE sorbent to preconcentrate the trace level of Pb(II), Mn(II), and Co(II). To investigate the extraction conditions, significant experimental parameters were examined in details. LODs were calculated as 0.022, 0.015, and 0.024 ng mL^-1 for Pb(II), Mn(II), and Co(II), respectively. The biosorption capacities of R. brevipes immobilized γ-Fe₂O₃ were calculated as 43.1 mg g^-1 for Pb(II), 54.9 mg g^-1 for Mn(II), and 49.7 mg g^-1 for Co(II). Pb(II), Mn(II), and Co(II) in food samples at trace levels were preconcentrated by applying the developed method.

Synthesis of Porous N-doped TiO2 by Using Peroxo Sol-Gel Method for Photocatalytic Reduction of Cd(II)

Porous N-doped TiO2 photocatalyst was successfully synthesized by an environmentally friendly peroxo sol-gel method using polyethylene glycol (PEG) as a templating agent. Here, the effect of PEG addition to the aqueous peroxotitanium solutions on the structure, pore properties and photocatalytic activity of the obtained photocatalysts was systematically studied. The prepared photocatalysts were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), and Brunauer-Emmett-Teller (BET). It was found that the doping of nitrogen narrows the band gap of TiO2 leading to enhance its visible-light response. The BET analysis shows that the prepared photocatalysts have a typical mesoporous structure with pore sizes of 3–6 nm. The photocatalytic activity of the prepared photocatalysts was evaluated by photocatalytic reduction of Cd(II) in an aqueous solution under visible light irradiation. The results show that porous N-doped TiO2 with the optimal PEG addition had the highest Cd(II) reduction of 85.1% after 2.5 h irradiation in neutral aqueous solution. This significant improvement in photocatalytic activity of the prepared photocatalysts was mainly attributed to the synergistic combination of N doping and porous structure, which could actively increase the catalytic active site of this photocatalysts. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

The crucial role of heavy metals on the interaction of engineered nanoparticles with polystyrene microplastics

Despite continuous research on microplastics (MPs), studies exploring the complexity of interaction between MPs and other aqueous constituents in multi-solute systems are scarce. In this study, the uptake and release of nanoceria (CeNPs) by various polystyrene MPs (PSMPs) were investigated. Results showed that PSMPs in the presence of heavy metals (HMs) exhibited a substantially higher sorption affinity for isotropic charged CeNPs than PSMPs alone; this enhanced affinity was attributed to the formation of PSMP-HM-CeNP complexes. FE-SEM imaging reaffirmed that CeNP clusters adhered to PSMP surfaces in the presence of HMs. Such attachment varied dependent on valence state, atomic size of coexisting metal cations, surface texture, and functionalities of MPs. The HM-mediated complex formation on PSMP particles was suppressed at higher ionic strength because of competitive sorption and double-layer compression. Subsequent release of MP-adhered CeNPs and HMs varied significantly between aquatic media and various simulated digestive fluids, verifying the crucial role of MPs for transfer of engineered nanoparticles (ENPs) from natural environments into biota via ingestion of MPs and trophic transfer. Our results highlight the enhanced potential for MPs to accumulate and to transport ENPs when metallic contaminants are present, which adds to the current understanding of the environmental fate and adverse effects of MPs along with various waterborne contaminants in actual environments.

Assessment of Zinc, Lead, Chromium, and Cobalt in Commonly Consumed Herbal Medicines in Sindh, Pakistan

Herbal medicines are widely consumed by the people of Pakistan for the treatment of various diseases. In the current study, quantitative assessment of four heavy metals namely zinc, lead, chromium, and cobalt was carried out in forty commonly consumed herbal medicines purchased from the markets of Khairpur and Sukkur, Pakistan. The conventional wet acid digestion method was used for the dissolution of samples and the concentration of heavy metals was determined by using flame atomic absorption spectrometry. Varied concentrations of metals were observed in different herbal medicines. The levels of Zn, Pb, Cr, and Co were in the range of 7.05-87.5 ppm, 5.62-44.9 ppm, 3.16-14.1 ppm, and 5.69-9.88 ppm, respectively. The findings of our study were compared with the WHO maximum permissible limits of these metals and it was observed that most of the analyzed samples exceeded the permissible levels. Keeping in view the levels of these metals in the selected herbal medicines, the prolonged intake of these drugs might be hazardous for human beings.

Highly selective and sensitive colorimetric chemosensor based on tricarboyanine for detection of Ag+ in industrial wastewater

Abstract

An efficient fluorescent probe 1 based on tricarbocyanine derivative was designed and synthesized, which can detect Ag+ in real industrial wastewater. UV-Vis absorption and fluorescent emission spectra of probe 1 were carried out and indicated this probe can bind Ag+ via complexation reaction, then leading to a remarkable color change from blue to light red. Furthermore, probe 1 showed high sensitive performance and excellent selectivity toward Ag+ over other common metal ions in neutral pH. The sensing mechanism was proposed and further confirmed by 1H NMR, which demonstrate analyte-induced destruction of the π-electron system could be shorten by the disruption of the pull-push π-conjugation system in probe 1. Moreover, a test strip was prepared by filter paper immersing in probe 1 solution, which further provide its potential application for trace Ag+ detection in real industrial wastewater.

Graphical abstract

Chitosan coated magnetite nanoparticle as a working electrode for determination of Cr(VI) using square wave adsorptive cathodic stripping voltammetry

The application of chitosan coated magnetite nanoparticle modified carbon paste electrode as a working electrode (chitosan@Fe₃O₄/CPE) for Cr(VI) analysis is presented. The electrochemical detection mode of square wave adsorptive cathodic stripping voltammetry (SWAdCSV) was selected for determination of Cr(VI) due to the high sensitivity and selectivity. The optimal conditions for electrode preparation and the electrode behavior including parameters affecting the SWAdCSV signal were investigated. Two linear ranges of Cr(VI) determination were observed 0.01-0.3 μg L^-1 and 0.5-30 μg L^-1 with limits of detection of 0.0061 and 0.078 μg L^-1, respectively. The precision of the electrode output in terms of %RSD was 11.4% (n = 30). The method was successfully applied to determine Cr(VI) in drinking water and sea water samples with recovery percentages in range 87-110%. Moreover, the results obtained agree with a paired t-test at the 95% confidence level which were comparable to the standard UV-visible spectrophotometric method.

Chemical activity relation of phosphorus and nitrogen presence in trace elements incorporation into underground water

Anthropogenic activities can deteriorate the quality of groundwater destined for human use and consumption due to the fact that human activities cause changes in groundwater chemistry. The changes are induced by chemical species coming from industrial waste, which interacts with rocks and minerals. These trigger agents (phosphorus and nitrogen nutrients) which can incorporate trace elements (As, Fe, Mn, Pb, Cd, Ni, Zn). The main objective of the present work was to study the phosphate ions' and nitrogenous species' effects on the incorporation of trace elements into groundwater used for human consumption and to determine the physicochemical processes that participate in the incorporation of trace elements. The physicochemical analysis and elemental analysis by ICP of the groundwater that supplies the study area showed that the phosphorus (P) activity contributes in the incorporation of trace elements into the water. Significant correlations between the activities of P and Fe (0.516), Mn (0.553), Pb (0.756), and As (- 0.747) as well as the correlation of NH₄⁺ with As indicate that the presence of chemical species such as PO₄^3- (2.50-32.20 mg L^-1), NO₃^- (0.89-30.80 mg L^-1), and NH₄⁺ (0.2-12.70 mg L^-1) are triggering agents that favor the dissolution and mobility of As (0.014-0.020 mg L^-1), Fe (0.020-1.14 mg L^-1), Mn (0.007-0.254 mg L^-1), Ni (0.002-0.0141 mg L^-1), Zn (0.009-0.459 mg L^-1), and Pb (0.009-0.0170 mg L^-1), species with adverse health effects because they are considered carcinogenic. Adequate control of the nitrogenous and phosphated material prevents the dissolution and mobility of trace elements into the water.

Water quality assessment of the most important dam (Latyan dam) in Tehran, Iran

A pattern of water quality affected by the input regime and site specification is one of the most important issues in water supply resources and demand management. The present study aims to assess the water quality of Latyan dam, the important reservoir that supplies drinking water of Tehran, the capital city of Iran. Monthly water sampling was performed at four depths of the dam. The physical and chemical properties of water including temperature, pH, turbidity, total dissolved solids (TDS), electrical conductivity (EC), hardness, as well as Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^-, SO₄^2-, silica, ammonium, nitrate, nitrite, and total phosphorus (TP) concentration, were monitored from May 2014 to January 2017. The results of statistical analysis indicated that the quality of water in the dam was affected by the depth in view of five variables of EC, pH, turbidity, SO₄^2-, and TP (p ˂ 0.05). Moreover, it was determined that ten out of 17 variables including EC, turbidity, TDS, Ca²⁺, K, Cl^-, SO₄^2-, silica, nitrate, and TP were statistically significant (p ˂ 0.05) based on seasonal variation analyses. Comparing the mean values, it could be concluded that EC, TDS, Ca²⁺, K⁺, Cl^-, and SO₄^2- were slightly higher during the winter probably owing to the diluting effects of seasonal precipitation. Nutrient-like distribution, nitrate, and TP, as well as silica, were much higher during the spring representing a high-diatoms activity and eutrophication. Turbidity was higher in the fall compared to the other seasons, which also demonstrated rainfall effects. Evaluation of the aggressiveness index (AI) suggests that water is moderately corrosive, and noncorrosive in the winter compared to other seasons. Moreover, according to the findings of this research and their comparison with the national and international water quality guidelines/standards, it could be said that the water quality of Latyan dam during the study period was acceptable and thus it was usable as a drinking water supply. However, due to the changes occurred in nitrate and phosphorus and extensive development of eutrophication problem, accurate and continuous evaluation of water quality in this reservoir is deemed necessary.