Green analytical methods of metals determination in biosorption studies

Carcinogenic and non-carcinogenic human health risk assessments of heavy metals contamination in drinking water supplies in Iran: a systematic review

The contamination of water due to heavy metals (HMs) is a big concern for humankind; particularly in developing countries. This research is a systematic review, conducted by searching google scholar, Web of Science, Science Direct, PubMed, Springer, and Scopus databases for related published papers from 2010 to July 2021, resulting in including 40 articles. Among the analyzed HMs in the presented review, the average content of Cr, Pb, Ba, Al, As, Zn, and Cd exceeded the permissible limits suggested by the World Health Organization (WHO) and 1,053 Iranian standards. Also, the rank order of Hazard Quotient (HQ) of HMs was defined as Cd>As>Cr>Pb>Li for children which means Cd has the highest non-carcinogenic risk and Li has the least. This verifies to the current order As>Cr>Pb>Fe=Zn=Cu>Cd for adults. The corresponded values of HQ and Hazard Index (HI) in most cities and villages were investigated and the results indicated a lower than 1 value, which means consumers are not at non-carcinogenic risk (HQ). Carcinogenic risk (CR) of As in the adult and children consumers in most of the samples (58.82% of samples for both groups) were investigated too, and it was more than>1.00E-04 value, which determines that consumers are at significant CR.

A new method for extraction and pre-concentration of the heavy metals using a microemulsion system in winsor II equilibrium and determination by HR-CS AAS

For the very first time, a microemulsion system in the Winsor II (WII) equilibrium was applied in a sample preparation method for extraction and pre-concentration in the determination of Pb, Cd, Co, Tl, Cu and Ni, in natural waters by high resolution continuum source atomic absorption spectrometry (HR-CS AAS). The method was optimized using the graphite furnace atomization. A simplex-centroid design for determine optimum extraction condition (77.5% aqueous phase, 5% of the oil phase, and 17.5% cosurfactant/surfactant ratio - C/S = 4) was applied. The optimized time for the sample preparations was around 30 min. The analytical performance of the optimized method using HR-CS GF AAS showed that the detection limits were: 0.09, 0.01, 0.06, and 0.05 μg L-1 for determination of Pb, Cd, Tl, and Co, respectively and the enrichment factors were between 6 and 19, considered excellent for all analytes. The RSD values were lower than 5%, demonstrating the good precision of the proposed method. When the optimized method was applied using the HR-CS F AAS, the sensibility increased 9 to 12 times for Cu and Ni, respectively. The analytical method was successfully applied for the determination of analytes in Certified Reference Material and real samples for natural waters such as Brackish water (recovery between 107 and 112%), Saline water (recovery between 83 and 94%), Produced water from oil industry (recovery between 98 and 110%) and Fresh water (recovery 80 and 87% to Cu and Ni respectively). All the results confirming the accuracy of the analytical method proposed. The repeatability of the measurements has been better 5% (n = 3), for all elements.

Potential Use of Low-Cost Agri-Food Waste as Biosorbents for the Removal of Cd(II), Co(II), Ni(II) and Pb(II) from Aqueous Solutions

We evaluated the potential use of agri-food waste for the removal of heavy metal ions from aqueous solutions and its application in different processes (e.g., water remediation, in the production of biomass enriched in nutritionally significant elements, etc.). Biomasses from grape seed, grape pomace, loquat seed, Calabrese broccoli stem, empty pods of carob and broad bean pods, unripe bitter orange peel, kumquat, orange pulp and Canary Island banana pulp were prepared. The percentages and biosorption capacities were evaluated and compared with those refe-renced using Valencia orange peel (Citrus sinensis Valencia late). These studies allow for easily providing added value to different agri-food wastes. The results show that the proposed biomasses were able to retain the studied metal ions and obtained different percentages, being in some cases above 90%. The highest values were obtained using broad bean pod (Pb(II) (91.5%), Cd(II) (61.7%), Co(II) (40.7%) and Ni(II) (39.7%)). Similar values were observed using grape seed, broccoli stem, carob pod and unripe bitter orange peel. Carob pod for biosorption of Cd(II) is also of great interest. These studies suggest that the agri-food residues evaluated can be applied to prepare effective biosorbents of divalent metal ions from aqueous solutions.

A Green Approach Based on Micro-X-ray Fluorescence for Arsenic, Micro- and Macronutrients Detection in Pteris vittata

In this study, benchtop micro-X-ray fluorescence spectrometry (µXRF) was evaluated as a green and cost-effective multielemental analytical technique for P. vittata. Here, we compare the arsenic (As) content values obtained from the same samples by µXRF and inductively coupled plasma-optical emissions spectrometry (ICP–OES). To obtain samples with different As concentrations, fronds at different growth time points were collected from P. vittata plants grown on two natural As-rich soils with either high or moderate As (750 and 58 mg/kg). Dried samples were evaluated using multielement-µXRF analysis and processed by PCA. The same samples were then analysed for multielement concentrations by ICP–OES. We show that As concentrations detected by ICP–OES, ranging from 0 to 3300 mg/kg, were comparable to those obtained by µXRF. Similar reliability was obtained for micro- and macronutrient concentrations. A positive correlation between As and potassium (K) contents and a negative correlation between As and iron (Fe), calcium (Ca) and manganese (Mn) contents were found at both high and moderate As. In conclusion, we demonstrate that this methodological approach based on μXRF analysis is suitable for monitoring the As and element contents in dried plant tissues without any chemical treatment of samples and that changes in most nutrient concentrations can be strictly related to the As content in plant tissue.

Comparison of non-destructive techniques and conventionally used spectrometric techniques for determination of elements in plant samples (coniferous leaves)

Conventionally used spectrometric techniques of inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma optical emission spectrometry (ICP-MS) usually involve time-consuming sample preparation procedure of a sample dissolution which requires the usage of aggressive and toxic chemicals. The need for suitable and sustainable analytical methods for direct multi-elemental analysis of plant samples has been increased in recent years. Spectrometric techniques for direct sample analysis, instrumental neutron activation analysis (INAA) and X-ray fluorescence (XRF) have been applied in environmental studies and various fields of screening tests. Nevertheless, these techniques are not commonly used for plant sample analysis and their performances need to be evaluated. This research aimed to assess how reliable non-destructive techniques are in the determination of elements in plants compared to conventionally used spectrometric techniques. A total of 49 plant samples of four conifer species (Pinus nigra, Abies alba, Taxus baccata and Larix decidua) were measured using two conventionally applied (ICP-MS, ICP-OES) and two non-destructive techniques (wavelength dispersive XRF (WD-XRF), INAA). The comparison was performed by investigation of relative ratios of concentrations and by correlation analysis. Moreover, precision of the techniques was examined and compared. The quality control included analysis of NIST pine needles certified reference material (1575a) using all examined techniques. Our results suggest that additional analytical and quality control steps are necessary for reaching the highest accuracy of multi-elemental analysis.

Potentiodynamic Electrochemical Impedance Spectroscopy of Polyaniline-Modified Pencil Graphite Electrodes for Selective Detection of Biochemical Trace Elements

In this study, we analyzed the application of potentiodynamic electrochemical impedance spectroscopy (PDEIS) for a selective in situ recognition of biological trace elements, i.e., Cr (III), Cu (II), and Fe (III). The electrochemical sensor was developed using the electropolymerization of aniline (Ani) on the surface of the homemade pencil graphite electrodes (PGE) using cyclic voltammetry (CV). The film was overoxidized to diminish the background current. A wide range of potential (V = −0.2 V to 1.0 V) was investigated to study the impedimetric and capacitive behaviour of the PAni/modified PGE. The impedance behaviors of the films were recorded at optimum potentials through electrochemical impedance spectroscopy (EIS) and scrutinized by means of an appropriate equivalent circuit at different voltages and at their corresponding oxidative potentials. The values of the equivalent circuit were used to identify features (charge transfer-resistant and double layer capacitance) that can selectivity distinguish different trace elements with the concentration of 10 μM. The PDEIS spectra represented the highest electron transfer for Cu (II) and Cr (III) in a broad potential range between +0.1 and +0.4 V while the potential V = +0.2 V showed the lowest charge transfer resistance for Fe (III). The results of this paper showed the capability of PDEIS as a complementary tool for conventional CV and EIS measurement for metallic ion sensing.

The Biosorption Capacity of Saccharomyces Cerevisiae for Cadmium in Milk

This study aimed to evaluate the capacity of Saccharomyces cerevisiae for Cadmium absorption in milk. Nowadays, one of the most serious problems of the industrialized world is heavy metal pollution. Applying microorganisms as novel biotechnology is very useful, especially in foodstuffs. Among the biosorbents used for heavy metal removal, Saccharomyces cerevisiae has received increasing attention due to its popularity in the food industry. In this regard, the effects of some important factors such as the initial metal concentration, biomass concentration and contact time on the biosorption capacity of Saccharomyces cerevisiae were studied. The biosorption was analyzed by the inductively coupled plasma mass spectrometer (ICP-MS). The maximum cadmium (Cd) removal (70%) was at 80 μg/L of Cd concentration in milk samples containing 30 × 108 CFU Saccharomyces cerevisiae at the end of storage time (the 4th day). There were no significant differences in the sensory and physicochemical properties (pH, acidity and density) of milk samples during storage (p < 0.05). The isotherm studies were followed by two popular models, Langmuir and Freundlich, and the results showed a better fit to the Langmuir isotherm. Altogether, the results of this study demonstrate that the approach of using this valuable yeast could be applied for food detoxification and producing healthier foodstuffs.

Natural Nanocolloids Mediate the Phytotoxicity of Graphene Oxide

Nanocolloids (Ncs) are ubiquitous in natural surface waters. However, the effects of Ncs on the fate and ecotoxicity of graphene oxide (GO, a popular engineered nanomaterial (ENM)) remain largely unknown. Ncs exhibit strong adsorption affinity (K_L = 1.93 L/mg) and high adsorption capacity (176.2 mg/g) for GO. After Ncs hybridization, GO nanosheets became scrolls, and the aggregation rate of GO decreased. The influence of humic acid and Ncs on GO toxicity was compared. Humic acid mitigated the phytotoxicity of GO. However, GO and GO-Ncs were found to have an envelopment effect on algal cells, and both could enter algal cells. GO-Ncs induced higher reactive oxygen species (ROS) generation, stronger DNA damage and plasmolysis, and more obvious inhibition of photosynthesis compared to GO. Proteomic analysis revealed that photosystem I- and II-related proteins (e.g., E1ZQR2 and E1ZPG5) were regulated more significantly in the GO-Ncs groups than in the GO groups. A combined proteomic and metabolomic analysis showed that inhibition of carbohydrate, fatty acid, and amino acid metabolism contributed to ROS generation. Given the high concentrations and activity of Ncs, the above results highlight the need for reconsideration of the Ncs-mediated environmental behaviors and risks of ENMs and other pollutants.

Enhanced reductive removal of ciprofloxacin in pharmaceutical wastewater using biogenic palladium nanoparticles by bubbling H2

To treat waste with waste and efficiently remove the organic pollutant, waste palladiums(ii) were adsorbed and reduced on microorganism surface to catalyze the reductive removal of ciprofloxacin in pharmaceutical wastewater. By optimizing conditions such as pH and temperature, the amount of biogenic palladium adsorbed and reduced on E. coli reached 139.48 mg g⁻¹ (Pd/microorganisms). Moreover, most of the Pd(ii) was reduced to nanometer-sized Pd(0) as characterized by TEM and SEM with EDXA. Using the obtained biogenic palladium, the reductive removal of ciprofloxacin is up to 87.70% at 25 °C, 3.03 folds of that achieved in the absence of H₂. The results show that waste E. coli microorganisms can efficiently adsorb and remove waste Pd(ii) and produce Bio-Pd nanoparticle catalysts in the presence of H₂. This biogenic palladium presents high catalytic activity and great advantages in the reductive degradation of ciprofloxacin. Our method can also be applied to other waste metal ions to prepare the biogenic metals, facilitate their recovery and reuse in degrading organic pollutants in wastewater to achieve “treating waste using waste”.

A solution has been successfully introduced to three key challenges from the wastewater containing waste microorganisms, metal and ciprofloxacin, respectively.