Separation and preconcentration of lead, chromium and copper by using with the combination coprecipitation-flame atomic absorption spectrometric determination

Environmental health risk assessment and source apportion of heavy metals using chemometrics and pollution indices in the upper Yamuna river basin, India

River Yamuna is the largest tributary of the Ganges with great economic importance, and provides water for about 57 million people and accounts for more than 70% of Delhi's water supply. Various pollution indices and chemometric methods were used to investigate heavy metal pollution, associated risks, and probable sources in the upper Yamuna river water. A total of 56 river water samples, 28 each in pre and post-monsoon season were collected and analysed for 15 heavy metals. The findings reveal that Al (38.66 ± 21.14 μg/L), As (16.52 ± 15.81 μg/L), and Mn (41.06 ± 89.25 μg/L) in pre-monsoon and Al (45.77 ± 29.46 μg/L), As (10.30 ± 12.15 μg/L), Fe (48.03 ± 81.11 μg/L), and Mn (31.02 ± 70.13 μg/L) in post-monsoon exceeded the Bureau of Indian Standards (BIS) acceptable limits. The pollution indices (HPI, NPI, HEI, and Cd) indicate that most locations are low to moderately polluted, except for the lower catchment. Health indices, i.e., hazard Index (HI) and incremental lifetime cancer risk (ILCR), suggest that the prolonged consumption of river water may cause potential human health hazards. In contrast, the water is suitable for domestic and other uses as the dermal risk is less prominent. The ecological risk index (ERI) of pre (0.22-58.75) and post-monsoon (0.12-44.21) were in the low-risk category (<110), indicating no ecological risk associated with heavy metals. In pre and post-monsoon, four principal components (PCs) described 73.97% and 76.18% of the total variance respectively, suggesting the mixed impact of numerous geogenic and anthropogenic sources in the region's water chemistry. Cluster analysis demonstrates that the lower catchment samples (National Capital Region, Delhi) significantly vary from each other due to wastewater discharge, industrialisation, and rapid urbanization, while the upper and mid-catchment samples are less distinct. Hence, more than 90% of the Yamuna water is extracted from the upper region; present findings may aid in developing an effective catchment scale management strategy.

Assessment of potentially toxic metal(loid)s contamination in soil near the industrial landfill and impact on human health: an evaluation of risk

The generation of solid waste is increasing with each passing day due to rapid urbanization and industrialization and has become a matter of concern for the international community. Leachate leakages from landfills pollute the soil and can potentially harm the human health. In this paper, inductively coupled plasma-optical emission spectrometric studies were employed to assess and analyze the composition of metals (Ba, Cd, Pb, Hg, Cu, Cr and Mn) and metalloid (As) in soil samples. Results of Cr, Mn, Cu, As, Ba, Cd, Pb and Hg from CRM (certified reference material, SRM 2709a) of San Joaquin soil were evaluated and reported in terms of percent recoveries which were in the range of 97.6-102.9% and show outstanding extraction efficiency. Other than copper, where the permitted limit set by the EU is specified as 50-140 mg/kg in soil, the average amount of all the metals in soil was found within the permissible limits provided by WHO, the European Community (EU) and US EPA. Soil contaminated with Hg (PERI = 100) and Cd (PERI = 145.50) posed an ecological risk significantly. Pollution load index (PLI) value is greater than 1, while degree of contamination (Cdeg) value is less than 32 which indicated that the soil is polluted and considerably contaminated with metals and metalloid, respectively. In terms of the average daily dosage (ADD) of soil, children received the highest doses of all metals (ADDing = 1.315 × 10-7 - 2.470 × 10-3 and ADDderm = 9.939 × 10-7 - 5.292 × 10-11), whereas ADDing (1.409 × 10-8 - 2.646 × 10-4) was found greater in adults. For all metals except for Ba, the hazard quotient (HQ) trend in both children and adults was observed to be HQing > HQderm > HQinh of soil. Children who are at the lower edge of cancer risk had a lifetime cancer risk (LCR) of 2.039 × 10-4 for Cr from various paths of soil exposure.

Mesoporous Ag-functionalized magnetic activated carbon-based agro-waste for efficient removal of Pb(II), Cd(II), and microorganisms from wastewater

Herein, eco-friendly mesoporous magnetic activated carbon-based agro-waste nanosorbents incorporating antimicrobial silver nanoparticles (Mag@AC1-Ag and Mag@AC1-Ag) have been prepared. Various techniques (XRD, SEM/EDX, TEM, FTIR, and BET analysis) were employed to characterize the prepared nanosorbents before being utilized as novel nanosorbents to remove Pb+2 and Cd+2 ions. Mag@AC1-Ag and Mag@AC1-Ag exhibited rapid and excellent uptake of Pb+2 and Cd+2. The pseudo-second-order kinetics and the Langmuir isotherm are more suitable for the explanation of the experimental results. The thermodynamic parameters showed that the Pb+2 and Cd+2 sorption by the nanosorbents was a spontaneous and endothermic reaction. The prepared nanosorbents can be effectively regenerated using HCl and recycled up to the fifth cycle. These nanosorbents' potential uses for eliminating Pb+2 and Cd+2 from real water samples were evaluated. Moreover, the results revealed that both Mag@AC1-Ag and Mag@AC2-Ag exhibited high antimicrobial activity against fecal coliform (gram-negative) and Bacillus subtilis (gram-positive).

Efficient Reduction of Cr(VI) with Carbon Quantum Dots

Hexavalent chromium (Cr(VI)) pollution is a global problem, and the reduction of highly toxic Cr(VI) to less toxic Cr(III) is considered to be an effective method to address Cr(VI) pollution. In this study, low-toxicity carbon quantum dots (CQDs) were used to reduce Cr(VI) in wastewater. The results show that CQDs can directly reduce Cr(VI) at pH 2 and can achieve a reduction efficiency of 94% within 120 min. It is observed that under pH higher than 2, CQDs can activate peroxymonosulfate (PMS) to produce reactive oxygen species (ROS) for the reduction of Cr(VI) and the reduction efficiency can reach 99% within 120 min even under neutral conditions. The investigation of the mechanism shows that the hydroxyl groups on the surface of CQDs can be directly oxidized by Cr(VI) because of the higher redox potential of Cr(VI) at pH 2. As the pH increases, the carbonyl groups on the surface of CQDs can activate PMS to generate ROS, O₂ ^•-, and ¹O₂, which result in Cr(VI) being reduced. To facilitate the practical application of CQDs, the treatment of Cr(VI) in real water samples by CQDs was simulated and the method reduced Cr(VI) from an initial concentration of 5 mg/L to only 8 μg/L in 150 min, which is below the California water quality standard of 10 μg/L. The study provides a new method for the removal of Cr(VI) from wastewater and a theoretical basis for practical application.

Toxic and heavy metals contamination assessment in soil and water to evaluate human health risk

Due to urbanization and industrialization, there has been an increase in solid waste generation and has become a global concern and leakage of leachate from landfills contaminate the soil and groundwater and hence can have a severe impact on human health. The present study aimed to determine the composition of toxic metals (Cr, Mn, Cu, As) and heavy metals (Cd, Ba, Hg, Pb) in soil and water by an inductively coupled plasma optical emission spectrometer (ICP-OES). To ensure accuracy during the analysis of Cr, Mn, Cu, As, Cd, Ba, Hg, and Pb in real samples, certified reference material (CRM, SRM 2709a) of San Joaquin soil and water (SRM 1640a) were analyzed and results were presented in terms of % recovery studies. The mean concentration of all the metals in soil and water did not exceed the limit set by the European Community (EU), WHO, and US EPA except Cu where the permissible limit defined by the EU is 50-140 mg/kg in soil. The soil is uncontaminated to moderately contaminated with respect to all metals except the Cu and Pb. Among the average daily dose (ADD) of soil, ADDing and ADDinh for children had the maximum dose for all metals than adults while ADDderm was higher in adults. Hazard quotient (HQ) trend in both adults and children was found in order HQing > HQderm > HQinh of soil for all metals except Ba which followed HQing > HQinh > HQderm. Hazard index (HI) values of soil for Cr and Pb in children were 7 and 7.5 times higher than adults respectively. Lifetime cancer risk (LCR) value for Cr by different exposure pathways of soil was 5.361 × 10-4 for children which are at the lower borderline of risk for cancer.

Micro solid phase extraction of cadmium and lead on a new ion-imprinted hierarchical mesoporous polymer via dual-template method in river water and fish muscles: Optimization by experimental design

In the present study, a new class of hierarchical silica based imprinted mesoporous polymers was fabricated by ion imprinting technology and it was applied to simultaneous selective extraction of cadmium and lead ions by micro solid phase extraction (μ-SPE). The biological nanocrystalline cellulose (BNCC) was prepared via acid catalyzed hydrolysis of cotton wool. The hierarchical silica (HS), as a substrate material, was synthesized via dual-template method, using BNCC and cetyltrimethylammonium bromide (CTAB) as hard and soft templates respectively. The structure and functional groups was characterized by Fourier infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray diffraction (XRD) and nitrogen adsorption-desorption. The results indicate that the as-prepared material has a hierarchical mesoporous structure with high specific surface area and high adsorption capacity for Cd(II) and Pb(II). The optimum experimental conditions in the proposed procedure were determined by response surface methodology (RSM) based on Box Behnken Design (BBD) and then it was successfully applied to determine Cd(II) and Pb(II) ions in the river water and fish samples.

Hydrothermal synthesis of a novel nanolayered tin phosphate for removing Cr(iii)

In this work, an outstanding nanolayered tin phosphate with 15.0 Å interlayer spacing, Sn (HPO₄)₂·3H₂O (SnP–H⁺), has been synthesized by conventional hydrothermal method and first used in the adsorptive removal of Cr(iii) from aqueous solution. A number of factors such as contact time, initial concentration of Cr(iii), temperature, pH, and ionic strength on adsorption were investigated by batch tests. Moreover, the isothermal adsorption characteristics and kinetic model of Cr(iii) onto SnP–H⁺ were studied. The results showed that the adsorption of Cr(iii) by SnP–H⁺ was in accordance with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model. The adsorption capacity of Cr(iii) onto SnP–H⁺ at temperature 40.0 °C and pH 3.0 could reach 81.1 mg g⁻¹. And the distribution coefficient K_d was 23.0 g L⁻¹. Overall, experiments certified that SnP–H⁺ was an excellent adsorbent that can effectively remove Cr(iii) from aqueous solution.

In this work, an outstanding nanolayered tin phosphate with 15.0 Å interlayer spacing, Sn (HPO₄)₂·3H₂O (SnP–H⁺), has been synthesized by conventional hydrothermal method and first used in the adsorptive removal of Cr(iii) from aqueous solution.

Efficient lead preconcentration using two chemically functionalized carbon nanotubes in hyphenated flow injection-flame atomic absorption spectrometry system

Lead contamination in drinking and natural water has reached alarming concentrations, thus necessitating the development of accurate and rapid determination systems for Pb(II) in aqueous systems. Two hyphenated flow injection-solid phase extraction- FAAS (FI-SPE-FAAS) systems using oxidized and m-phenylenediamine functionalized multiwalled carbon nanotubes for Pb(II) preconcentration from industrially contaminated real water samples have been proposed. The chemical and hydrodynamic parameters affecting Pb(II) sorption/desorption were optimized. The effect of common interfering ions in water was also studied. Different figures of merit such as preconcentration factor (> 70), detection limit (≤ 1.5 µg L^-1), and relative standard deviation (≤ 1.3%) were achieved at the preconcentration time of 120 s for both the preconcentration systems. The method was applied to industrially contaminated real water samples and the spike recovery tests were carried out using standard Pb(II) solution traceable to NIST. The proposed method was validated using standard reference material 1640a supplied by NIST Gaithersburg, MD, USA.

Ultrasonic-assisted micro solid phase extraction of arsenic on a new ion-imprinted polymer synthesized from chitosan-stabilized pickering emulsion in water, rice and vegetable samples

Pickering emulsion polymerization has been employed for the Ultrasonic assisted-micro solid phase extraction (UA-µSPE) of ultra trace arsenic species by a new magnetic ion imprinted polymer (MIIP) prior to hydride generation atomic absorption spectrometry. 2-acetyl benzofuran thiosemicarbazone (2-ABT) as a new chelating agent and core- shell hydrophobic magnetic nanoparticles was synthesized and the polymerization was carried out at the presence of arsenic - ligand complex, crosslinker, monomer, initiator, stabilizing agent and water-oil emulsion magnetic carrier. In second step, the nanoparticles and polymers were characterized. The analytical parameters such as pH, amount of polymer and ultrasonic time were selected and optimozed by Plackett-Burman and Box-Behnken designs respectively. Linear dynamic range, detection limit and relative standard deviation were 0.01-85.000 µg·L^-l, 0.003 µg·L^-l, and 3.21%, respectively. The proposed preconcentration procedure was successfully applied to the determination of arsenic ion in a wide range of food samples with different and complex matrixes.

A magnetic ion-imprinted polymer composed of silica-coated magnetic nanoparticles and polymerized 4-vinyl pyridine and 2,6-diaminopyridine for selective extraction and determination of lead ions

A novel, sensitive and highly selective magnetic ion-imprinted polymer for facile separation and preconcentration of trace quantities of Pb(ii) ions.

Synthesis and application of a novel core-shell-shell magnetic ion imprinted polymer as a selective adsorbent of trace amounts of silver ions

Ion-imprinted polymer (IIP) technology has received considerable attention for its greatest potential application. In this work, a novel magnetic nano ion-imprinted polymer (MIIP) for the selective and sensitive pre-concentration of silver (I) ions were used. It was obtained using Fe3O4@SiO2@TiO2 nanoparticles as a magnetic support of adsorbent, Ag(I)-2,4-diamino-6-phenyl-1,3,5-triazine (DPT) complex as the template molecule and methacrylic acid (MAA), 2,2′-azobisisobutyronitrile (AIBN), ethylene glycol dimethacrylate (EGDMA), as the functional monomer, the radical initiator and crosslinker, respectively. The synthesized polymer nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET). Silver ions were separate from the polymer and measured by flame atomic absorption spectrometry (FAAS). The maximum adsorption capacity of the novel imprinted adsorbent for Ag(I) was calculated to be 62.5 mg g−1. The developed method was applied to the preconcentration of the analyte in the water, radiology film and food samples, and satisfactory results were obtained.

Separation of Molybdenite from Chalcopyrite in the Presence of Novel Depressant 4-Amino-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one

In this paper, 4-amino-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one (ATDT) was synthesized and introduced as a depressant for selective flotation separation of molybdenite from chalcopyrite. Its flotation performance and adsorption mechanism on minerals were first investigated by flotation, UV spectra, zeta potential, Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy Measurements (XPS). The bench scale tests indicated that ATDT exhibited stronger depressing power than chalcopyrite, and the selective index of Mo/Cu improved significantly in the presence of ATDT. The results of the UV spectra, zeta potential and FTIR demonstrated that ATDT chemisorbed on the chalcopyrite surface. The XPS results further confirmed that ATDT might chemisorb onto the chalcopyrite surface through S and N atoms to form five-membered chelate rings and a postulated adsorption mode was presented. For molybdenite, the different measurements agreed well with each other and implied that ATDT might weakly physisorb onto a molybdenite surface.

A new coprecipitation method without carrier element for separation and preconcentration of some metal ions at trace levels in water and food samples

A new simple and sensitive preconcentration, separation and environmentally friendly method based on carrier element free coprecipitation (CEFC) was developed using 4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (APSAL) as a new organic co-precipitant to precipitate Cr(3+), Cu(2+), Fe(3+), Pb(2+) and Zn(2+) ions from water and food samples. The levels of the studied elements were detected by flame atomic absorption spectrometry (FAAS). The impact of several analytical parameters, such as pH, sample volume and coprecipitant amount as well as centrifugation rate and time was investigated to recover the examined metal ions. The influence of matrix ions was also tested, and no interferences were observed. The recovery values of the analyte ions were calculated and found to be in the range of 95-101%. The detection limits, corresponding to three times the standard deviation of the blank (N=10), were found to be in the range of 0.2-1.2 μg L(-1). The relative standard deviation (RSD) was calculated to evaluate the precision of the proposed method and was found to be ≤5.0%. The calculated preconcentration factor was 100. The proposed method was successfully applied to separate and preconcentrate trace amounts of ions in several water and food samples. To confirm the accuracy and validate the proposed method, certified reference materials were analyzed with satisfactory results.

Simultaneous column preconcentration of ultra trace amounts of heavy metals with nano-adsorbent in some environmental and biological samples

In the present investigation, multi-walled carbon nanotubes impregnated by 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane were prepared and applied as adsorbent for the simultaneous separation of Bi(III), Cu(II), Cd(II) and Pb(II) ions prior to their determination by electrothermal atomic absorption spectrometry. The following analytical figures of merit were determined for bismuth, copper, cadmium and lead, respectively: enrichment factors of 168, 134, 111 and 146, assay precisions of ±4.6%, ±4.8%, ±5.3% and ±5.0% and detection limits of 11.3, 3.7, 0.5 and 0.3 ng L(-1). The method was successfully applied for the determination of heavy metals in environmental, biological and certified reference materials.

Dispersive liquid-liquid microextraction of lead(II) as 5-(4-dimethylaminobenzylidene) rhodanine chelates from food and water samples

A dispersive liquid-liquid microextraction procedure for lead(II) as its 5-(4-dimethylaminobenzylidene) rhodanine complex has been established prior to its microsampling flame atomic absorption spectrometric determination. The influences of various analytical parameters including pH, solvent type and volume, dispersive solvent type and volume, 5-(4-dimethylaminobenzylidene) rhodanine amount, salt effect, and centrifugation time and speed were investigated. The effects of certain alkali, alkaline earth, and transition metal ions on the quantitative extraction of lead(II) were also studied. Quantitative recoveries were obtained at pH 6. The enrichment factor was calculated as 125. The detection limit for lead is 1.1 μg/L. The accuracy of the method was tested with the additions recovery test and analysis of the standard reference materials (SPS-WW2 waste water, NIST SRM 1515 apple leaves, and TMDA-51.3 fortified water). Applications of the present procedure were tested by analyzing water and food samples.

Solid phase extraction of heavy metal ions from agricultural samples with the aid of a novel functionalized magnetic metal–organic framework

This work describes synthesis of a novel magnetic metal–organic framework to preconcentrate the trace amounts of heavy metals. (a) Functionalized Fe₃O₄ by ethylenediamine. (b) Synthesis of the magnetic MOF nanocomposite.

Pilot test of pollution control and metal resource recovery for acid mine drainage

The study was undertaken in order to recover the metal resources from acid mine drainage (AMD). A 300 m(3)/d continuous system was designed and fractional precipitation technology employed for the main metals Fe, Cu, Zn, and Mn recovery. The system was operated for six months using actual AMD in situ. The chemicals' input and also the retention time was optimized. Furthermore, the material balance was investigated. With the system, the heavy metals of the effluent after the Mn neutralization precipitation were below the threshold value of the Chinese integrated wastewater discharge limit. The precipitates generated contained 42%, 12%, 31%, and 18% for Fe, Cu, Zn, and Mn, respectively, and the recovery rates of Fe, Cu, Zn, and Mn were 82%, 79%, 83%, and 83%, respectively. The yield range of the precipitate had significant correlation with the influent metal content. Using the X-ray diffraction analysis, the refinement for Fe, Cu, and Zn could be achieved through the processes of roasting and floatation. Cost-benefit was also discussed; the benefit from the recycled metal was able to pay for the cost of chemical reagents used. Most important of all, through the use of this technology, the frustrating sludge problems were solved.