Extraction Of Arsenic Research Articles

Development of cost-effective inorganic arsenic extraction method for resource-limited regions: Analysis of efficiency and regulatory implications

This study evaluated the effectiveness of coke and lemonade extraction methods compared to the standard 1 % v/v HNO3 method for determining inorganic arsenic (iAs) concentrations in rice bran samples using a field-deployable method (Arsenator field kit). The limit of detection (LOD) for the methods was 45 μg kg−1, comparable to existing literature. The extraction efficiencies were assessed by comparing iAs recovery rates, with coke extraction yielding the highest recovery of 127.4 %, followed by lemonade at 116.2 %, and HNO3 at 100 %. Statistical analysis indicated strong correlations between the extraction methods, particularly between HNO3 and coke (Pearson correlation coefficient, 0.990), suggesting that coke extraction is a reliable alternative to the traditional HNO3 method. However, lemonade extraction showed a lower correlation (0.940) and higher false negative rates, indicating potential limitations for regulatory compliance. Notably, at the maximum contaminant limit (MCL) of 0.100 mg kg−1, coke extraction produced an 8 % false positive rate with no false negatives, while lemonade extraction had an 8 % false positive rate and a 17 % false negative rate. This study underscores the potential of coke extraction as a cost-effective and efficient alternative for assessing iAs levels in rice products, especially in resource-limited settings. Recommendations include the standardization of coke extraction protocols and the development of robust monitoring programs to ensure food safety and public health protection against arsenic contamination. Overall, the findings contribute valuable insights for improving arsenic detection methods and regulatory compliance in food safety practices.

Extraction of arsenic from fine dust of copper smelters by reduction roasting with natural gas

One of the current trends in the complex processing of fine dust from copper smelters is their direct leaching with sulfuric acid. As practical results show, high reliable technological parameters are not achieved due to the high content of arsenic in dust. During sulfuric acid leaching of dust, arsenic is distributed between the lead cake and the solution at a ratio of 40 and 60%, respectively. The redistribution of arsenic between leaching products significantly reduces the technological performance and leads to the accumulation of arsenic in the technological scheme. The paper presents the results of comprehensive studies of the elemental and phase composition of fine dust from one of the copper smelters in Kazakhstan. In the initial dust, along with the main phases presented in the form of lead and zinc sulfate, the following typical components were found: oxides of copper, lead, zinc and copper and zinc ferrites. Arsenic is found in two forms—As(III) and As(V). The laboratory installation and technique for conducting reduction roasting of dust with natural gas are presented. The influence of roasting duration, temperature and natural gas consumption on the extraction of arsenic from dust was studied. It has been established that almost complete, up to 99%, extraction of arsenic from dust is achieved with optimal technological roasting parameters: duration τ = 40 min.; natural gas consumption is 1.5 times higher than the stoichiometrically required amount for the reduction of As2O5, and temperature 500 °C.

Application of green solvents for arsenic removal from petroleum produced water: Statistical, DFT and McCabe-Thiele determination

This work presents the novel application of green oils to extract arsenic ions from petroleum produced water via liquid-liquid extraction (LLE). In the experiment, the removal of arsenic ions from synthetic petroleum produced water is investigated, using five green oils: canola oil, corn oil, linseed oil, rice bran oil, and sunflower oil, in place of petroleum-based solvents: toluene and kerosene. Both extraction and stripping optimizations are examined. For extractants, Aliquat 336 and Cyanex 921 are implemented. The initial arsenic concentration (3.984 mg L−1) of petroleum produced water is examined. Results demonstrate that Aliquat 336 in corn oil proved to be most effective for arsenic removal. At optimal conditions via response surface methodology (RSM), the highest extraction and stripping percentages reached 99.95 % and 100.00 %, respectively. In accordance with the World Health Organization (WHO) levels of ≤0.01 mg L−1, arsenic concentration remaining in the extracted water (0.002 mg L−1), is seen to fulfill the requirement needed. The extraction and stripping kinetics are of first and second-order. Mechanisms of arsenic removal are evaluated via density functional theory (DFT). Further, selectivity, recycling of the organic phase, and the number of stages via McCabe-Thiele theory are determined under optimal conditions.

Comprehensive recovery of arsenic and valuable metals from lead smelting flue dust: Process optimization and mechanism investigation

The comprehensive recovery of arsenic and valuable metals from lead smelting flue dust have received widespread attention due to its extremely high toxicity and economic value. In this research, a clean process which consisted of pressure oxidation leaching, preferential separation of Zn and Cd, reduction of As(Ⅴ) and recovery of indium was proposed. Thermodynamic calculation of leaching process suggested that the increasing of temperature reduces the redox potential required for the oxidation of As3+ to As5+, and the optimal conditions were found to be at acid concentration of 100 g/L, oxygen pressure of 2.0 MPa, temperature of 170 °C, L/S of 10 mL/g, leaching time of 2.5 h and agitating speed of 500 r/min. Under the selected conditions, the leaching extents of As, Cd, In, Sb and Zn are 99.17 %, 98.96 %, 92.68 %, 40.23 % and 96.63 %, respectively, while lead remained in the leaching residue. The separation of arsenic and other valuable metals in leachate is the most difficult and critical section of the process, where As2S3 was particularly added to the acid solution in certain manner to preferentially precipitate Zn and Cd in the forms of ZnS and CdS, subsequently reduce As(Ⅴ) to As(Ⅲ). Experiments by adding arsenic filter cake furtherly confirmed the reducibility of As2S3 and realized simultaneous extraction of arsenic in arsenic cake and acid leaching solution. Eventually, arsenic was recovered as As2O3 with a high purity of 98.56 % and the total extraction extent of indium is 93.76 %.

Development of a dispersive liquid–liquid microextraction procedure based on a natural deep eutectic solvent for ligand-less preconcentration and determination of heavy metals from water and food samples

In the current study, a ligand-less dispersive liquid–liquid microextraction technique assisted ultrasound and vortex equipment (DLLME-A-US-V) procedure was used for the simultaneous preconcentration and extraction of heavy metal ions. The proposed method was done by a natural hydrophobic deep eutectic solvent for the extraction of arsenic, cadmium, lead, and mercury ions without a complexing agent. The natural deep eutectic solvent was prepared from l-menthol (M) and salicylic acid (SA). The precursor of deep eutectic solvents strongly affects the extraction of metal ions. Among the studied solvents, hydrophobic deep eutectic solvents showed the highest extraction recovery. Under optimal experimental conditions, the method linearity, limits of detection (LOD), limits of quantification (LOQ), relative standard deviations (RSD %), enrichment factors (EF), and extraction recovery (% ER) were equal to 0.005–14 µg/L, 0.0043–0.0088 µg/L, 0.0143–0.0294 µg/L, 1.66–2.83 %, 112–120, and 90–96 %, respectively. The obtained coefficients of determination (r2) were also higher than 0.991. This method was successfully applied to determine some heavy metals in food samples in the ultra-trace range with the recovery values of real samples being 93–108 %.

Solvent Extraction with Cyanex 923 to Remove Arsenic(V) from Solutions.

The removal of harmful arsenic(V) from aqueous solutions using Cyanex 923 (solvation extractant) was investigated using various experimental variables: equilibration time, the acidity of the aqueous phase, temperature, extractant and arsenic concentrations, and O/A ratio. Cyanex 923 extracted As(V) (and sulfuric acid) from acidic solutions; however, it could not be used to remove the metal from slightly acid or neutral solutions. The extraction of arsenic is exothermic and responded to the formation of H3AsO4·nL species in the organic phase (L represents the extractant, and the stoichiometric factor, n = 1 or 2, depends on the acidity of the aqueous phase). Extraction isotherms are derived from the experimental results. Both arsenic and sulfuric acid loaded onto the organic phase can be stripped with water, and stripping isotherms are also derived from the experimental results. The selectivity of the system against the presence of other metals (Cu(II), Ni(II), Bi(III), and Sb(III)) is investigated, and the ability of Cyanex 923 to extract As(V) and sulfuric acid compared to the use of other P=O-based solvation reagents, such dibutyl butylphosphonate (DBBP) and tri-butyl phosphate (TBP), is also investigated.

Застосування міцелярної екстракції для визначення арсену методом атомно-емісійної спектрометрії з індуктивно-зв'язаною плазмою у низці фармацевтичних препаратів

Application of cloud-point extraction for arsenic determination in pharmaceuticals of various types: Calcium gluconate, solution for injection 100 mg mL-1, Potassium chloride, solution for injection 4 %, and Magnesium sulfate, solution for injection 25 %, was investigated. It has been demonstrated that direct quantitative extraction of arsenic into the micellar phase of Triton X-100 in the form of molybdoarsenic acid is possible only for potassium chloride. Magnesium sulfate requires at least five times dilution for arsenic to quantitatively enter the micellar phase. In the case of calcium gluconate, the organic anion is likely to have a higher affinity for the Triton X-100 phase than molybdoarsenic acid resulting in very low extraction coefficient values. In this case, decomposition of the drug was suggested. Three decomposition methods were evaluated and compared: acid decomposition in an open system, acid decomposition in a microwave reactor, and ashing with MgO/Mg(NO3)2. The second and third methods provide further quantitative removal of arsenic, the second being more rapid and easier to perform.

Synergistic effect of arsenic removal from petroleum condensate via liquid-liquid extraction: Thermodynamics, kinetics, DFT and McCabe-Thiele method

This work presents the purification of petroleum condensate by removing arsenic ions via liquid-liquid extraction (LLE). Influence of pure and synergistic extractants is investigated. In terms of the practicability, following parameters are examined: the type of extractant, operating time, and temperature. Response surface methodology is used to design parameters such as organic-aqueous ratio and extractant concentration. Under optimal conditions; a mixture of 1 mol/L HCl and 0.02 mol/L thiourea with an organic/aqueous ratio of 1:4 at 323.15 K for 60 min, the extraction of arsenic reached 78.2 %. Further, batch simulation via two-stage counter-current extraction, and estimation by McCabe-Thiele diagram proved to be enhanced arsenic extraction to 95.3 %. Analysis by FTIR show that arsenic ions in petroleum condensate are formed as triphenylarsine compound ((C6H5)3As). The process of arsenic removal proved to be zero-order endothermic, irreversible and spontaneous reaction. The results obtained from the density functional theory (DFT) confirm that arsenic ions react with the synergistic extractant: effectively forming a covalent bond (As–S).

Thiourea-assisted selective removal of arsenic from copper smelting flue dusts in NaOH solution

The selective removal of arsenic from copper smelting flue dusts is of great significance for environmental protection and resource recycling. This study employed thiourea assisted alkaline leaching to selectively extract arsenic from copper smelting flue dusts. The effects of NaOH concentration, thiourea concentration, temperature, leaching time and pulp density on the dissolution of arsenic, zinc, lead, copper and antimony in NaOH solution were studied. The results show that the addition of thiourea can effectively promote extraction of arsenic while inhibiting the leaching of zinc, lead and copper in copper smelting flue dust. Under the optimized leaching conditions, the leaching efficiencies of arsenic and antimony were 98.5% and 1.62%, respectively, while zinc, lead and copper were not leached. X-ray diffraction (XRD) analysis suggested that the addition of thiourea promoted the dissolution of insoluble arsenate minerals. The combined results of scanning electron microscopy (SEM), mineral liberation analysis (MLA), and X-ray photoelectron spectroscopy (XPS) demonstrated that thiourea prevented sulfide products from forming a coating on arsenic surface. This work has important implications for the development of processing technologies for arsenic-containing materials.

Extraction of Pb, Cu, Zn and As from Fine Dust of Copper Smelting Industry via Leaching with Sulfuric Acid

Fine dust from copper smelting plants is an important source of raw materials for the extraction of various valuable metals. A specific feature of dust from copper smelting plants in Kazakhstan is their high arsenic content of up to 15%. This work shows the possibility of hydrometallurgical processing of fine dust from copper smelters, obtained during the converting of copper mattes through the Vanyukov process, via direct leaching with sulfuric acid. The influence of temperature, process time and the S:L (solid/liquid) ratio on the selective extraction of Pb, Zn, Cu and As into targeted products under leaching conditions is studied. The results of the test work show that with the optimal process parameters of S:L = 1.5, t = 60 °C, τ = 60 min, the extraction of copper and zinc into solution is achieved as 89% and 96%, respectively, and lead into cake by up to 97%. The relatively low extraction of copper and zinc into the solution is explained by the transition of copper and zinc ferrites that are insoluble in sulfuric acid into the lead cake. The redistribution of arsenic between the leaching products established in this case also affects the reduction in copper and zinc in the solution. The extraction of arsenic into the solution is 49.32%. More than half of the arsenic from the dust is left in the lead cake. The concentration of arsenic in lead cake will lead to its transition into circulating dust during smelting. This will increase the accumulation of arsenic in the overall process flow. Therefore, when organizing dust-processing technology, it is necessary to provide measures for the preliminary removal of arsenic.

A novel block copolymer containing gadolinium oxide nanoparticles in ultrasound assisted-dispersive solid phase microextraction of total arsenic in human foodstuffs: A multivariate optimization methodology

A new poly(3-hydroxy butyrate)-b-poly(dimethyl amino ethyl methacrylate) amphiphilic block copolymer containing gadolinium oxide nanoparticles (PHB-PDMAEMA-Gd2O3-NPs) were synthesized and used as composite adsorbent for extraction of total arsenic. Characterization of the composite adsorbent material PHB-PDMAEMA-Gd2O3-NP was studied using spectroscopic techniques. Plackett-Burman design and central composite design were employed to screening and optimization of the experimental parameters. This composite adsorbent was utilized in ultrasound assisted-dispersive solid phase microextraction (UA-dSPµE) for the determination of total inorganic arsenic in foodstuffs through hydride generation atomic absorption spectrometry (HG-AAS). It demonstrates a linear relationship across arsenic concentration range of 0.07–1.12 µg/L with a correlation coefficient (0.996). It’s showed an enrichment factor of 128 and a limit of detection 0.02 µg/L for total inorganic arsenic determination. Accuracy of the developed method was confirmed through the analysis of certified reference materials with 96.0–98.5% recovery. It proved to be significantly useful UA-dSPµE method for determining total inorganic arsenic in different foodstuffs.

Arsenic extraction from copper concentrate using controlled oxidative roasting and filtration process

For more efficient treatment of arsenic-bearing copper concentrates, arsenic can be extracted in two steps: high-temperature filtration of dust and low-temperature separation of condensed arsenic oxide. The oxygen content in the roasting environment has an important effect on the residual arsenic content in the concentrate. When the oxygen content is high, the arsenate formed remains in the concentrate. When the oxygen content is low, the formation of arsenic sulphide can clog the filter cake residue. Roasting at 700 °C with an oxygen content of 4 vol.% results in the lowest residual arsenic content in the concentrate, from 11.8 to 0.34 wt.%. In the pilot experiment, the oxygen content was indirectly controlled by controlling the feed rate. The residual arsenic content is reduced to 0.48 wt.% and the purity of the recovered As2O3 reaches 99.17 wt.%. Based on the study of the mechanism of arsenic change with different oxygen contents, a new process of oxygen-controlled roasting is proposed and successfully applied in the pilot test, so that the residual arsenic content in copper concentrates is lower than the standard of arsenic content in imported minerals from China (0.5 wt.%).

Simultaneous determination of various heavy metal and arsenic ions in seafood using functionalized fibrous silica (KCC-1) coated stir bar sorptive extraction prior to inductively coupled plasma mass spectrometry

Heavy metal ions (HMIs) and arsenic ion with high bioavailability and toxicity in seafood pose a serious threat to human health by food chain. Herein, the functionalized fibrous silica (KCC-1) nanoparticles bearing thiol (-SH) and amine (-NH2) groups respectively were synthesized, characterized, and coated on stir bar sorptive extraction (SBSE) of trace cadmium (Cd), mercury (Hg), lead (Pb), copper (Cu), and arsenic (As) ions simultaneously in seafood prior to inductively coupled plasma mass spectrometry (ICP-MS). The optimal SBSE variables, such as sample pH (3–7), elution composition (1 M HNO3 and 0–4% (m/v) thiourea), and sample volume (5–25 mL), were optimized. The optimal sample pH (6), elution composition (1 M HNO3 and 2% (m/v) thiourea), and sample volume (20 mL), were obtained. The performance of KCC-1-SH SBSE method was superior to the KCC-1-NH2 SBSE method in terms of linearity (0.9981–0.9992), limit of detection (LOD, <0.08 μg kg−1), limit of quantification (LOQ, <0.60 μg kg−1), recovery (85.6–106.6%), and repeatability and reusability (no apparent loss in extraction efficiency after 18 times). The maximum residual limits of Cd, Hg, Pb, Cu, and As (V) in mussel, shellfish, and shrimp were all below 1, 1, 1.5, 20, and 76 mg kg−1, respectively. The results demonstrated that the method has a great potential for the daily monitoring of trace HMIs in these seafood products.

Synthesis and functionalization of cross-linked molecularly imprinted polymer (MIP) microwave-assisted for recognition and selective extraction of lead (II) and arsenic (V) from water: Isotherms modeling and integrative mechanisms

A cross-linked molecularly imprinted polymer (MIP) was synthesized and functionalized by metal oxide nanoparticles (TiO2 and SiO2) to form a potential cross-linked (MIP) nanocomposite via binding of Nano-TiO2 and Nano-SiO2 to cross-linked chitosan. Where chitosan acted as a functional monomer, glutaraldehyde (Glu) acted as an organic cross-linker with bifunctional reactive groups, and lead (II) and arsenic (V) acted as templates. This work is composed of a binary of promising ideas: (a) a facile preparation of cross-inked molecularly imprinted polymer (MIP) via bulk polymerization method, and (b) the functionalization of newly fabricated cross-linked (MIP) using metal oxide nanoparticles. The fabricated cross-linked biopolymer nanocomposite was used for simultaneous and selective recovery of toxic metal ions from water. Microwave irradiation was applied as an assisted technique to estimate the performance of the synthesized material. The properties and structure of the fabricated Nano-TiO2@Cross-linked Chitosan@Nano-SiO2 were characterized by FT-IR, XRD, TG/DTA, BETs, SEM-EDX, TEM, and XPS. The results indicated that Pb(II) at pH 5.0 ± 0.15 and at time varied from 5 sec to 25 sec exhibited recoveries capacity 97.99–99.81% and Qmax 81.97 mg/g, while As(V) at pH 4.0 ± 0.15 and at 5 sec to 20 sec, exhibited recoveries capacity 96.38–99.72 % and Qmax 625.00 mg/g. The cross-linked MIP nanocomposite exhibited an improved specific surface (388.0 m2/g) and mesopore size (15.18 nm) compared to its precursors. Freundlich and pseudo-second-order equation well-fitted the experimental data. Pb(II) and As(V) recoveries were exothermic, spontaneous, and governed by entropy change. Solvents subjected to eliminate the templates, interfering ions, selectivity, and reusability experiments were carried out. Newly integrative mechanisms for implementing cross-linked (MIP) nanocomposite for recognizing and recovering metal ions were adequately explained.

Bacteria immobilized onto carbon nanofiber as a composite for effective removal of arsenic from wastewater

Drinking arsenic-contaminated water is one of the major fears for the health of mankind due to its being of highly toxic and carcinogenic substance. In this perspective, the present work is aimed to prepare Enterococcus faecalis (E. faecalis) immobilized onto carbon nanofiber (CNF) as novel composite sorbent and evaluate it adsorption ability for removal of arsenic ions As(III) from aquatic medium. The Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM)/Energy Dispersive X-Ray (EDX) analysis results displayed that the modification of CNF particles with E. faecalis makes more sorptive sites and the surface functional groups for binding arsenic ions. The designing of the experiment (DOE) methodology was applied to assess the effects of experimental factors on the sorption yield and their significance levels. The designing of factorials was utilized to estimate responses and statistical correlation among experimental parameters. The response surface plots exhibited that the response was higher at an optimum level of variables used in the extraction of arsenic. The equilibrium data under optimized sorption conditions (temperature 24 °C, contact time 30 min, biosorbent amount 500 mg/L and pH 5) were studied for Langmuir and Freundlich isotherms and the data were well fitted to the Langmuir isotherm with obtained maximum removal capacity of 255.2 mg g−1 for monolayer As(III) sorption onto E. faecalis/CNF composite. The sorption mechanism for kinetic studies followed the pseudo-second order model with obtained correlation coefficient (R2 = 0.998). Based on characterization and surface functionalities the proposed adsorption mechanism, the hydrogen bonding, π–π and electrostatic attractions were efficient for bisorption of As(III) onto E. faecalis /CNF composite.

Development of a Two-Stage Hydrometallurgical Process for Gold-Antimony Concentrate Treatment from the Olimpiadinskoe Deposit.

An integrated two-stage metallurgical process has been developed to process concentrates from the Olimpiadinskoe deposit, which contain high levels of antimony and arsenic. The optimal parameters for the alkaline sulfide leaching process of the initial concentrate from the Olimpiadinskoe deposit were determined to achieve the maximum extraction of antimony at a 99% level. The recommended parameters include an L:S ratio of 4.5:1, a sodium sulfide concentration of 61 g/L, a sodium hydroxide concentration of 16.5 g/L, a duration of 3 h, and a temperature of 50 °C. A synergistic effect of co-processing alkaline sulfide leach cakes with sulfuric and nitric acids was observed. The pre-treatment step reduced the nitric acid composition by converting carbonates into gypsum and increased the arsenic extraction by 15% during subsequent nitric acid leaching. The laboratory research on the nitric acid leaching of decarbonized cake established the key parameters for the maximum iron and arsenic extraction in solution (92% and 98%, respectively), including an L:S ratio of 9:1, a nitric acid concentration of 6 mol/L, and a time of 90 min. Full polynomial equations for the iron and arsenic extraction from the decarbonized cake were derived. The model demonstrated a high relevance, as evidenced by the determination coefficients (R2) of 96.7% for iron and 93.2% for arsenic. The technology also achieved a high gold recovery rate of 95% from the two-stage alkaline sulfide and nitric acid leach cake. Furthermore, the maximum deposition of arsenic from the nitrate leach solution in the form of insoluble As2S3 was determined to be 99.9%. A basic technological flow sheet diagram for processing the flotation gold-antimony concentrate from the Olimpiadinskoe deposit was developed, including two stages: the production of metallic antimony and the gold extraction from the nitric leach cake.

Insight into the plant-associated bacterial interactions: Role for plant arsenic extraction and carbon fixation

This study investigated the interactions between rhizosphere and endosphere bacteria during phytoextraction and how the interactions affect arsenic (As) extraction and carbon (C) fixation of plants. Pot experiments, high-throughput sequencing, metabonomics, and network analysis were integrated. Results showed that positive correlations dominated the interconnections within modules (>95 %), among modules (100 %), and among keystone taxa (>72 %) in the bacterial networks of plant rhizosphere, root endosphere, and shoot endosphere. This confirmed that cooperative interactions occurred between bacteria in the rhizosphere and endosphere during phytoextraction. Modules and keystone taxa positively correlating with plant As extraction and C fixation were identified, indicating that modules and keystone taxa promoted plant As extraction and C fixation simultaneously. This is mainly because modules and keystone taxa in plant rhizosphere, root endosphere, and shoot endosphere carried arsenate reduction and C fixation genes. Meanwhile, they up-regulated the significant metabolites related to plant As tolerance. Additionally, shoot C fixation increased peroxidase activity and biomass thereby facilitating plant As extraction was confirmed. This study revealed the mechanisms of plant-associated bacterial interactions contributing to plant As extraction and C fixation. More importantly, this study provided a new angle of view that phytoextraction can be applied to achieve multiple environmental goals, such as simultaneous soil remediation and C neutrality.

The natural magnesite efficacy on arsenic extraction from water and alkaline influence on metal release in water

Arsenic (As) removal studies were carried out through batch experiments to investigate the performance of the locally available calcined magnesite mineral rocks from Tanzania. Natural water from a stream source in Tanzania and the prepared synthetic water at the laboratory were used for the studies. Parameters such as initial As concentration, calcined magnesite dosage, contact time and pH were evaluated for As removal using an overhead rea×2 shaker. Arsenic concentration was reduced from 5.3 to 1.1 mg/L As(V) at 180 min when 0.5 g/L calcined magnesite was applied to a synthetic water sample, whereas the concentration of 117 μg/L As(V) and 5.2 μg/L As(III) was reduced to below 0.1 μg/L in natural water. An increase in calcined magnesite dosage resulted in increased As removal up to below 0.01 mg/L. The calcined magnesite raised the pH of the water sample from 6.8 to 10 when the applied dosage increased between 0.002 g/L and 0.05 g/L. The pH was constant at around 10 even when the amount of 0.05 g/L was added 2000 times. Despite the high pH, the amount of magnesium released in water was low. The calcination of magnesite at 500 °C increased surface area by 4 times as compared to the natural magnesite and X-ray diffraction showed presence of MgCO3 phase as the dominant phase at this temperature. The reaction kinetics of As removal on 0.5 g/L calcined magnesite fitted with the pseudo-second-order (R2 = 0.96). Reaction isotherm was strongly fitted with Freundlich isotherm (R2 = 0.98). Linear regression and artificial intelligence neural network showed the As removal was influenced by both contact time and pH. Arsenic can be removed from As water using calcined magnesite and will be suitable for water treatment around gold mining areas.

Insight into direct phosphorus release from simulated wastewater ferric sludge: Influence of physiochemical factors

Phosphorous recovery from chemical phosphorus removal (CPR) plants is limited. CPR plants that use iron salts for phosphorous removal generate iron phosphate (Fe-P) rich sludge. This study investigates the influence of pH and competing anions (chloride), on phosphorus and soluble iron release from lab simulated Fe-P sludge. Factors influencing recovery, such as sludge age and Fe/P molar ratio are also investigated. Results showed that alkaline treatment of Fe-P sludge was not effective in releasing Fe (<3%) but effective in releasing P, particularly at controlled pH value of 10 where the %P release was (90 ± 2%). Sludge ageing time did not affect P release from Fe-P sludge at ages less than 5 days. However, a remarkable decrease in %P release (i.e., 50% reduction) was observed at ages of 9 and 11 days for pH values of 9–10. Arsenic extraction of exchangeable surface bound P from Fe-P sludge and surface area determination of hydrous ferric oxide (HFO) under different aging times supported qualitatively the internalization of surface bound P during aging, which is a proposed mechanism responsible for the decrease in P release for older sludge. Chloride effect in releasing P from Fe-P sludge was negligible. The reduction in P release by aging was best described by a zero-order kinetic model. Modeling with the PHREEQC geochemical software did not always agree with the measured release of phosphorus from the Fe-P sludge. PHREEQC assumes all surface sites for phosphorus are exchangeable and has no mechanism to represent phosphorus trapped within HFO particles.

Green approaches with amino acids-based deep eutectic solvents (AADES) for determining As in medicinal herbs by ICP-MS

In this work, an innovative ultrasound-assisted matrix solid-phase dispersion (UA-MSPD) method and microwave-assisted extraction (MAE) were applied with amino acids-based deep eutectic solvents (AADES) for the extraction of arsenic (As) from medicinal herbs. Multivariate optimization by Doehlert design (DD) was performed to determine the optimal experimental conditions. The effects of temperature (TP), time (TM), and sample-solvent ratio (SSR) were evaluated, and the optimized conditions were 50 °C, 60 min, and 10:1 mg mL−1 for UA-MSPD and 100 °C, 40 min, and 40:1 mg mL−1 for MAE, employing AADES 2 (β-alanine, citric acid, and water), where the hydroxyl and carboxyl groups of the citric acid structure favored formation of a chelate complex with the analyte. AADES 3 (β-alanine, xylitol, and water) was effective for MAE, while AADES 1 (β-alanine, malic acid, and water) proved to be inefficient for As extraction. The parameters of the analytical methods were evaluated using certified reference materials. The accuracy, based on percentage recovery, was in the range 77–101 %, while the limits of detection and quantification were in the ranges 0.010–0.039 mg kg−1 and 0.011–0.130 mg kg−1, respectively. The analytical curves presented R2 > 0.99. The proposed methods were shown to be environmentally friendly, based on the Analytical Eco-Scale and RGB 12 procedures. Both optimized methods were applied for the determination of As in commercial medicinal herbs (0.059–0.101 mg kg−1), with the values obtained being within the maximum daily intake limit established by the World Health Organization (WHO). It should be noted that there are no previous reports in the literature concerning the application of a sample preparation method using AADES, employing their solid precursors, with no requirement for prior solvent synthesis, as proposed here in the case of the UA-MSPD method.