Synthetic Water Samples Research Articles

Synergistic Nitrate Removal: Enhanced Efficiency with Zinc-Immobilized Calcium Cross-Linked Polyvinyl Alcohol Film

Nitrate is a major water contaminant causing eutrophication and poses health risks. Controlling its levels is essential. In this study, zinc powder immobilized calcium cross-linked polyvinyl alcohol (Zn-Ca-PVA) film was synthesized for the removal of nitrate from water samples. The results demonstrated an enhanced removal efficiency, increasing from 47.82% ± 1.14% for the film without zinc powder to 78.47% ± 5.20% with a maximum adsorption capacity of 9.56mgg−1 when using Zn-Ca-PVA with synthetic water samples. This enhancement suggests a synergistic mechanism in which nitrate is adsorbed onto the calcium cross-linked PVA film via electrostatic interaction, and then catalytically reduced by the zinc powder within the film, converting it into nitrogen-containing gas and removing it from the sample. Moreover, this synergistic approach resulted in high removal efficiencies for real water samples, ranging from 82.95% ± 0.98% to 96.19% ± 0.62%. The adsorption of nitrate aligned well with the Freundlich model, while the kinetic process aligned well with the pseudo-second-order model (R2 > 0.99). Thermodynamic studies revealed ΔG° values ranging from -2.71 to -3.76kJmol−1, ΔH° of 6.22kJmol−1, and ΔS° of 29.98Jmol–1 K–1, indicating spontaneous adsorption, an endothermic nature, and increased randomness at the solid/solution interfaces during nitrate adsorption. Furthermore, Zn-Ca-PVA exhibited tolerance to coexisting ions, with the removal efficiency of nitrate remaining largely unchanged (< 5%) even in the presence of mixed coexisting ions at five times higher concentrations. These findings highlight the promising potential of Zn-Ca-PVA films for practical applications in nitrate removal.

Adsorption of Cr(VI) Using Organoclay/Alginate Hydrogel Beads and Their Application to Tannery Effluent.

The tanning industry is among the most environmentally harmful activities globally due to the pollution of lakes and rivers from its effluents. Hexavalent chromium, a metal in tannery effluents, has adverse effects on human health and ecosystems, requiring the development of removal techniques. This study assessed the efficacy of organobentonite/alginate hydrogel beads in removing Cr(VI) from a fixed-bed adsorption column system. The synthesized organobentonite (OBent) was encapsulated in alginate, utilizing calcium chloride as a crosslinking agent to generate hydrogel beads. The effects of the volumetric flow rate, bed height, and initial Cr(VI) concentration on a synthetic sample were analyzed in the experiments in fixed-bed columns. The fractal-like modified Thomas model showed a good fit to the experimental data for the asymmetric breakthrough curves, confirmed by the high R2 correlation coefficients and low χ2 values. The application of organoclay/alginate hydrogel beads was confirmed with a wastewater sample from an artisanal tannery industry in Belén (Nariño, Colombia), in which a Cr(VI) removal greater than 99.81% was achieved. Organobentonite/alginate hydrogels offer the additional advantage of being composed of a biodegradable polymer (sodium alginate) and a natural material (bentonite-type clay), resulting in promising adsorbents for the removal of Cr(VI) from aqueous solutions in both synthetic and real water samples.

Removal of chromium and copper from synthetic water samples using passion fruit peels

In this work, modified passion fruit husk was used as biomass for the removal of chromium and copper present in the waters. PH, contact time, and particle size were considered experimental factors. Stirring speed, dosage, and temperature were considered constants. The results showed a 69% decrease in chromium using a pH 4, 90 min, and 300 μm composition. For copper, 74.4% was removed at pH 4, with 120 min and 300 μm, based on initial concentrations of 30 ppm for both metals. The results showed that passion fruit peel is a potential effective removal agent for chromium and copper in synthetic waters. This supports its possible application in the purification of metal-contaminated water, which could contribute to environmental protection.

Preparation, characterization, and evaluation of an acetylene black polyurethane composite electrode modified with copper nanoparticles for the determination of escitalopram

Escitalopram (ESC) is a widely prescribed antidepressive drug worldwide and must be monitored in biological fluids and environmental samples. Thus the preparation of an acetylene black-polyurethane composite electrode modified with copper metallic nanoparticles by electrodeposition intended for the determination of ESC in synthetic urine and mineral water samples is presented. The surface was further electrochemically pretreated in 0.50 mol L−1 NaOH in order to obtain a stable mixture of Cu (II) oxides on top of the Cu° nanoparticles. After preconditioning in 0.10 mol L−1 phosphate buffer pH = 7.0, the modified electrode was used in the determination of ESC in the proposed matrixes using CV and DPV, after optimizing experimental parameters. The interaction of the analyte with copper (II) ions promoted a decrease of the Cu(II) reduction peak which was proportional to the ESC concentration in the 0.020–0.10 µmol L−1 (LOD = (5 ± 1) nmol L−1) and 0.040–0.20 µmol L−1 (LOD = (5.1 ± 0.9) nmol L−1) in cyclic voltammetry (CV) and differential pulse voltammetry (DPV) respectively. Interferences from ascorbic acid, uric acid, dopamine and creatinine were evaluated, however the last one present in synthetic urine did not prevented the determination of ESC, as well as the other chemical species naturally present in the mineral water.

Association of rare earth elements with secondary mineral phases formed during alkalinization of acid mine drainage

Rare Earth Elements (REE) are present in acid mine drainage (AMD) in micromolar concentrations and AMD discharge may lead to an environmental risk. Alkaline Passive Treatment Systems (PTS) are often used to treat AMD and trap toxic trace elements. This study was set up to identify mechanisms by which REE are trapped in or on secondary phases formed in a PTS. Batch alkalinization experiments were performed to simulate PTS by sequentially increasing the pH of AMD collected from the Tharsis mining area inside the Iberian Pyrite Belt and synthetic AMD water samples via CaCO3 addition. The solids that precipitated up to pH ~4 and between pH 4–6 were collected and characterized by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in combination with Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM/EDX) and synchrotron-based X-ray Absorption Spectroscopy (XAS) and synchrotron-based Micro-X-ray Fluorescence (μ-XRF). Results reveal that REE are mostly scavenged between pH 4–6 in association with Al and Fe phases, whereas a smaller fraction is scavenged at pH ~4 by association with gypsum. Synchrotron-based analysis evidences the incorporation of La3+ into the gypsum structure by substituting Ca2+, indicating a co-precipitation mechanism with gypsum occurring mainly at low pH. Results from parallel adsorption and co-precipitation tests suggest that the REE scavenging between pH 4–6 could be due to a combination of adsorption and co-precipitation on Al(OH)3 and ferrihydrite. This implies that in PTS, REE would be mainly found in Al- (and Fe-) oxyhydroxides occurring in deeper layers of the PTS, i.e., where higher pH-values occur, though a small fraction, especially the light REE, could also be found incorporated into gypsum in the upper layers.

A fused convolutional transformer for voltammetric electronic tongue analysis tasks

Electronic tongue and artificial intelligence have been evaluated as new rapid analysis technologies in complex solution research. The use of nanomaterials to modify the screen-printed carbon electrode (SPCE) increased the specific surface area and electrocatalytic active sites of the electrode. The voltammetric electronic tongue utilizes multiple cross sensitive sensors to describe the overall characteristics of complex samples, and the complementary information between sensors provides rich and comprehensive descriptions for analyzing various components. The use of electronic tongue for rapid analysis of water quality has gradually become a trend, but the overlapping phenomenon of peaks formed by the similar redox potential of each component in water and the interference of the substrate makes it difficult to obtain effective information of each component in water quality. Here, we propose a Fused Convolutional Transformer model (FCvT) that removes the limitation of overlapping peaks by fusing local features and global complementary features to quantify components in complex solutions. The performance of FCvT was evaluated by testing synthetic water samples consisting of four standardized substance solutions and compared with partial least squares (PLS), support vector regression (SVR), artificial neural networks (ANN), and convolutional neural networks (CNN). The results show that the FCvT obtains the lowest mean absolute percentage error in the set of independent tests.The average quantization error of FCvT is reduced by 34.4 % relative to other methods.

Green synthesis of metal nanoparticles from Codium macroalgae for wastewater pollutants removal by adsorption

AbstractAlgae have adsorption properties and reducing agents due to their rich content. In this study, palladium nanoparticles (Pd NP), platinum nanoparticles (Pt NP), and iron oxide nanoparticles (Fe3O4 NP) were prepared from Codium macroalgae using green synthesis. The structure of the synthesized nanoparticles was elucidated by X‐ray diffractometry, Fourier transforms infrared spectroscopy, Brunauer–Emmett–Teller analysis, transmission electron microscopy, ultraviolet‐visible spectroscopy and scanning electron microscopy‐energy dispersive X‐ray spectrometry and their use as nanoadsorbents for the removal of pollutants from aqueous media was investigated in detail. Naproxen (NPX), an anti‐inflammatory drug, and the dyes methylene blue (MB) and cresol red (CR) were selected as pollutants for this study. Batch adsorption experiments were conducted using both real wastewater obtained from the Organised Industrial Zone of Isparta Province and synthetic water samples prepared with tap water from Burdur Province and pure water. Under optimum adsorption conditions, Pd NP showed significant efficiency in the real wastewater sample, with an adsorption capacity of 37.19 and 50.03 mg g–1 for CR and NPX, respectively, within 150 min. In comparison, Pt NP showed an adsorption capacity of 40.01 mg g–1 for MB within the same timeframe. These findings indicate that while Pd NP showed the highest adsorption capacity for both CR and NPX, Pt NP showed the highest adsorption capacity for MB. The Langmuir model and the pseudo‐second‐order equation were more suitable to describe the adsorption behavior of CR, MB, and NPX. In addition, studies on the desorption and reusability of the nanoadsorbents were carried out under the same optimum experimental conditions.

Lysine-functionalized graphene oxide on cost-effective microporous support: A hydrophilic and fouling resistant membrane for safe lead filtration

The presence of heavy metals in freshwater is a severe problem humanity faces. Remedies with high removal efficiency of heavy metals from contaminated water are crucial. However, existing studies often neglect effluent quality per World Health Organization (WHO) standards. Also, the reported conditions are either unrealistic to the actual contamination levels or unsuitable for large-scale applications. Here, we report the fabrication of zwitterionic graphene oxide (GO) by incorporating a pH-responsive group (i.e., Lysine) using N, N′-diisopropylcarbodiimide (DIC) as a coupling agent. The modified GO-Lys was then coated on a commercially available 0.45-μm Nylon membrane and was tested for selective removal of toxic heavy metals from synthetic water and human blood plasma samples while allowing essential metal ions. Consequently, lead was the most retained toxic metal (i.e., 99.99% retention with effluent quality meeting WHO standards) among nickel, arsenic, cadmium, and mercury (i.e., between 50 to 80% retention). These composite membranes also displayed excellent fouling resistance and inhibited bacterial adhesion onto the membrane surface, while maintaining stable performance over a long time and critical transmembrane pressure conditions. This research marks a significant advancement in environmental technologies, providing an effective solution for selectively removing heavy metal pollutants, with a particular focus on lead detoxification applications.

Is catalytic ozonation always an efficient treatment for refractory pollutant in various water matrices?

In this study, surrogate indicators (·OH yield and Rct value) were developed to identify whether homogeneous and heterogeneous catalysts should be added during ozonation of refractory pollutants. The abatement of atrazine (ATZ) was in the order of O3/H2O2 process (94 %) > O3/γ-Al2O3 process (70 %) > ozonation alone process (55 %) in synthetic water samples at pH 7, which was in agreement with the order of ·OH yield and Rct value. However, the abatement of ATZ during ozonation alone process (0.64–0.62) was higher than O3/H2O2 process (0.63–0.60) and O3/γ-Al2O3 process (0.48–0.49) in the presence of high dosage of humic acid (HA, 3.38 × 10−1–4.50 × 10−1 mg C/L) at pH 7. The abatement of ATZ was linearly proportional to ·OH yield, whereas it was not linearly proportional to Rct value in the synthetic water samples containing HA at pH7. The abatement of ATZ during ozonation alone process was higher than that during catalytic ozonation process by one-time ozone dosing method in real water. The abatement of ATZ during O3/H2O2 process and O3/γ-Al2O3 process were higher than that during ozonation alone process by three-time ozone dosing method in real water, which was linearly proportional to ·OH yield and Rct value. The residual DOM in phase III become recalcitrant to ozone, which could be decomposed by catalyst forming ·OH. Overall, this result implies that the comparison of ·OH yield and Rct value between ozone decay by DOM in various water matrices and by catalyst should be concerned before the addition of catalyst during ozonation process was applied in real water.

Detection of Trace Tin(II) by Salicylfluoroketone Complex Fluorescence Method

Based on the Sn(II)-salicylfluorescein (SAF)-cetyltrimethylammonium bromide (CTMAB) system, the complex fluorescence method was used to detect Sn(Ⅱ). The method was established by exploring the optimal reaction conditions, and the possible reaction mechanism was discussed. The results showed that the concentration of Sn(Ⅱ) had a good linear relationship with the fluorescence intensity of the system in the range of 0~0.40 µg/mL. The linear regression equation is ΔF = - 7.457 + 715.286ρ (µg/mL), which had a good linearity; the correlation coefficient is 0.9976, and the detection limit of the method was 0.0764 µg/mL. In the detection of Sn(Ⅱ) in synthetic water samples, laboratory wastewater, and canned pineapples, the recovery rates were 95.83%, 104.17%, and 100.0%, which showed good results.

RAPID EXTRACTIVE SPECTROPHOTOMETRIC DETERMINATION OF PALLADIUM(II) USING 5- CHLOROSALICYLALDEHYDE THIOSEMICARBAZONE

Quantitative extraction of the Pd(II) complex with 5-Chlorosalicylaldehyde thiosemicarbazone (CSTSC) was achieved at pH levels ranging from 3.6 to 4.4 after a 30-second equilibration period in n-butyl acetate. When the concentration of Pd(II) does not exceed 9.0 μg mL-1, the complex formed between Pd(II) and 5-Chlorosalicylaldehyde thiosemicarbazone complies with Beer's law, and it displays the highest absorbance at 400 nm. By means of the mole ratio method and the Jobs continuous variation method, it was determined that the stoichiometry of the Pd(II)-CSTSC complex is 1:2. The stability of the extracted complex persisted for 96 hours. The calculated Sandell's sensitivity was 9.92 x 10-3 μg cm-2, while the molar absorptivity was found to be 1.072 x 104 L mol-1 cm-1. Utilizing this method, effective analysis has been carried out on synthetic samples, complexes, and water samples.

Recovering Phosphate from Complex Wastewater Using Macroporous Cryogel Composited Calcium Silicate Hydrate Nanoparticles.

Since currently used natural, nonrenewable phosphorus resources are estimated to be depleted in the next 30-200 years, phosphorus recovery from any phosphorus-rich residues has attracted great interest. In this study, phosphorus recovery from complex wastewater samples was investigated using continuous adsorption on cryogel column composited calcium silicate hydrate nanoparticles (CSH columns). The results showed that 99.99% of phosphate was recovered from a synthetic water sample (50 mg L-1) using a 5 cm CSH column with a 5 mL min-1 influent flow rate for 6 h while 82.82% and 97.58% of phosphate were recovered from household laundry wastewater (1.84 mg L-1) and reverse osmosis concentrate (26.46 mg L-1), respectively. The adsorption capacity decreased with an increasing flow rate but increased with increasing initial concentration and column height, and the obtained experimental data were better fitted to the Yoon-Nelson model (R2 = 0.7723-0.9643) than to the Adams-Bohart model (R2 = 0.6320-0.8899). The adsorption performance of phosphate was decreased 3.65 times in the presence of carbonate ions at a similar concentration, whereas no effect was obtained from nitrate and sulfate. The results demonstrate the potential of continuous-flow phosphate adsorption on the CSH column for the recovery of phosphate from complex wastewater samples.

A PVC‐Membrane Cationic Surfactant Sensitive Potentiometric Sensor: Potentiometric Determination of Dodecyltrimethyl Ammonium Ion

AbstractA potentiometric poly (vinyl chloride) (PVC) membrane cationic surfactant‐selective sensor based on a dodecyltrimethylammonium‐phosphotungstate ion pair as an electroactive material was suggested for the determination of dodecyltrimethylammonium bromide. Membrane optimization studies revealed that the PVC membrane in the composition of 0.5 % dodecyltrimethylammonium‐phosphotungstate ion pair, 69.5 % o‐nitrophenyloctylether and 30.0 % PVC displayed the best potentiometric performance properties. The sensor exhibited a linear response to dodecyltrimethylammonium ions in the concentration range of 1.0×10−6–1.0×10−2 mol L−1 with a detection limit and sensitivity of 5.0×10−7 mol L−1 and 56.6 mV/decade, respectively. The response of the sensor to dodecyltrimethylammonium cation was quite stable, sensitive, selective and rapid (&lt;10 s). The life span of the sensor was found to be about 3 months. The analytical applications of the sensor were successfully carried out with the developed sensor as an indicator electrode for the determination of the end‐point of dodecyltrimethylammonium ions titration and dodecyltrimethylammonium contents of synthetic water samples.

High-precision zirconium isotope analysis of Pacific seawater reveals large mass-dependent fractionations in the ocean

Zirconium (Zr) stable isotopes recently emerged as potential tracers of magmatic processes and, as a result, their behavior in high-temperature environments have been the focus of extensive characterization. In contrast, few studies have focused on Zr behavior and isotopic fractionation in low temperature or aqueous environments. Here, we describe a new analytical routine for highly precise and accurate analysis of Zr isotopes of water samples, using a combination of double-spike and iron co-precipitation methods. To assess the impact of potential systematic biases a series of experiments were conducted on natural and synthetic water samples. Our results show that the spike-to-sample ratio, matrix composition, and high field-strength element (HFSE) concentration have negligible effects on measured seawater Zr isotopic compositions, and that the Fe co-precipitation method used yields accurate and precise Zr isotope data. We thus apply this method to natural seawater samples collected from a water column profile in the Pacific Ocean off the coast of California, with depths ranging from 5 to 711 m. We find that the natural seawater samples are highly fractionated relative to solid-Earth values and display marked variability in δ94/90Zr as a function of depth, ranging from ∼ +0.650 ‰ near the surface, to + 1.530 ‰ near the profile bottom, with an analytical uncertainty of ± ∼0.045 ‰ (2 SE, external reproducibility). The δ94/90Zr value of seawater is much higher than that of Earth’s mantle and continental crust, which has a δ94/90Zr value near zero, indicating the presence of processes in the hydrosphere capable of inducing large mass-dependent fractionation. Furthermore, the seawater δ94/90Zr value exhibits systematic variations with respect to water depth and salinity, suggesting that Zr isotopic compositions may be sensitive to seawater chemical properties and source highlighting its potential utility as a tracer of biogeochemical processes within the ocean.

Microcystin-LR Removal by Ozone (O3) and Vacuum-UV (VUV): The Effect of Chloride Ions

ABSTRACT Removal of microcystin-LR (MC-LR) by ozone (O3), vacuum-UV (VUV), and their combination was investigated in the presence of chloride as one of the main solutes present in water. In general, the combined VUV/O3 process provided the greatest MC-LR removal, with the presence of chloride enhancing the removal efficacy. Formation of chlorine radical species was the primary reason for the observed improvement. The order of MC-LR removal by different processes using UV fluence of around 300 mJ cm−2, ozone dose of 0.1 mg L−1, and chloride concentration of 120 mg L−1 was as follows: VUV/O3/Chloride > VUV/O3 > VUV/Chloride > VUV > O3. Comparing MC-LR removal by O3, VUV and VUV/O3 in synthetic lab samples, spiked with Suwannee River NOM and natural water samples of the same organic concentration, showed the significance of background organics in scavenging ozone in the process. For a given ozone dosage, MC-LR removal by O3 or VUV/O3 in natural water was lower than that in the synthetic water samples. The standalone VUV was not affected and the MC-LR removals were identical in both synthetic and natural waters.

Development of medium-scale filtration device for supplying drinking water during flood situations

A scaled-up device for rapid water treatment is presented based on technologies described in earlier effort (“Point of use drinking water filtration: A microfluidic solution providing safe drinking water during flood situation,” J. Water Process Eng. 52 (2023) 103545). It comprises inertia-based microfluidic filtration, selective ion-exchange, antimicrobial activated carbon, and ultraviolet disinfection stages. The overall performance of the device is tested using synthetic, field, and flood water samples. The size of the bypass port is optimized to achieve ∼99 % filtration efficacy. The length of IX media encapsulated in mini channels is adjusted by studying its effect in limiting the dissolved solids and the hydraulic resistance. The adsorption performance and capacity of the AC at equilibrium conditions is evaluated by tests using methylene blue. To augment the filtrate throughput, both unit and module level parallelization scheme is developed. Unit filters are arranged both in planar and vertical levels to form a parallelized module (PM). Subsequently, PMs are multiplexed with a carefully designed inlet distributary, outlet, and bypass collection network. The prototype device can treat nearly 400 L of raw water in six days of continuous operation. Integrated UV reactors in the full-scale device, show complete sterilization of the influent water.

The Potential Use of Moringa peregrina Seeds and Seed Extract as a Bio-Coagulant for Water Purification

Moringa is a genus with many applications; some of these applications can be linked to their use in traditional medicine and as a source of nutrients, and traditionally, some species have been used for water purification. Many studies have been conducted to assess the use of different species of Moringa for water purification. One of the species that is extensively studied is M. Oleifera because of its wide geographical distribution. There are limited studies on M. peregrina due to its limited geographical distribution, as it is native to the Arabian Peninsula and some other countries in the Middle East. The aim of this study is to assess the potential use of M. peregrina for water coagulation. This study was conducted using synthetic water samples as well as real, untreated wastewater samples to determine the potential of M. peregrina seeds for water coagulation. The results revealed that M. peregrina seed extract had better turbidity removal at 60 °C compared with the use of the seed extract at room temperature, and increasing the ionic strength of the extracting solution could also improve the efficiency of the seed extract in terms of turbidity removal. Furthermore, the de-oiled seed extract showed efficiency comparable with that of the raw seeds. Application to the real wastewater samples showed that the de-oiled seed extract showed percentage removal of 38%, 81%, and 74% for SCOD, turbidity, and color, respectively. Furthermore, the de-oiled M. peregrina seed extract at a dose of 200 mg/L equivalent to raw seeds was capable of removing 97.4%, 66.5%, 51.8%, 50.3%, and 45.8% of Mo, Cu, Cd, Cr, and Co, respectively.

A straightforward approach utilizing an exponential model to compensate for turbidity in chemical oxygen demand measurements using UV-vis spectrometry.

Recently, ultraviolet-visible (UV-vis) absorption spectrometry has garnered considerable attention because it enables real-time and unpolluted detection of chemical oxygen demand (COD) and plays a crucial role in the early warning of emerging organic contaminants. However, the accuracy of detection is inevitably constrained by the co-absorption of organic pollutants and turbidity at UV wavelengths. To ensure accurate detection of COD, it is necessary to directly subtract the absorbance caused by turbidity from the overlaid spectrum using the principle of superposition. The absorbance of COD is confined to the UV range, whereas that of turbidity extends across the entire UV-vis spectrum. Therefore, based on its visible absorbance, the UV absorbance of turbidity can be predicted. In this way, the compensation for turbidity is achieved by subtracting the predicted absorbance from the overlaid spectrum. Herein, a straightforward yet robust exponential model was employed based on this principle to predict the corresponding absorbance of turbidity at UV wavelengths. The model was used to analyze the overlaid absorption spectra of synthetic water samples containing COD and turbidity. The partial least squares (PLS) method was employed to predict the COD concentrations in synthetic water samples based on the compensated spectra, and the corresponding root mean square error (RMSE) values were recorded. The results indicated that the processed spectra yielded a considerably lower RMSE value (9.51) than the unprocessed spectra (29.9). Furthermore, the exponential model outperformed existing turbidity compensation models, including the Lambert-Beer law-based model (RMSE = 12.53) and multiple-scattering cluster method (RMSE = 79.34). Several wastewater samples were also analyzed to evaluate the applicability of the exponential model to natural water. UV analysis yielded undesirable results owing to filtration procedures. However, the consistency between the compensated spectra and filtered wastewater samples in the visible range demonstrated that the model is applicable to natural water. Therefore, this proposed method is advantageous for improving the accuracy of COD measurement in turbid water.

Increase the Efficiency of Dispersive Liquid-Liquid Microextraction (DLLME) and its Use for the Determination of Lead (II) in Aqueous Solutions

A simple, sensitive, and greener method for green extraction and preconcentration of lead from aqueous media and further assay by UV-Vis spectrophotometer has been developed using 1,5 diphenylthiocarbazone (dithizone). Several factors of dispersive liquid-liquid microextraction (DLLME) including the type and volume of extraction and dispersive solvents, shaking time, the concentration of dithizone as a complexing agent, and pH were optimized. Under optimum selected conditions, the limit of detection (LOD), the limit of quantification (LOQ), the linearity range, the relative standard deviation (RSD), and the Enrichment factor (EF) of the proposed method were obtained at 0.007 ppm, 0.025 ppm, 0.01-0.1 ppm, 4.3% (n = 3) and 40, respectively. This proposed method was successfully applied in the analysis of three synthetic water samples and good spiked recoveries over the range of 96.0–98.5% were obtained.

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.