Pb Solution Research Articles

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.

Effects of lead (Pb)-induced oxidative stress on morphological and physio-biochemical properties of rice

In rice, high concentration of lead (Pb) can cause phyto-toxicity affecting several physiological functions. Cultivation of rice varieties that are resistant to Pb-induced oxidative stress is an important management strategy in Pb-contaminated soils. In the current study, we evaluated four different rice cultivars for their response to Pb-induced stress. Three japonica type cultivars X-Jigna, Ediget, and Furat, and one Indica type cultivar Amber 33 were grown in soil containing different Pb concentrations (0 mM, 0.6 mM, and 1.2 mM). The soil was treated with 0 mM or 0.6 mM or 1.2 mM Pb solution one month prior to rice seedling transplantation. Thereafter, four-week-old rice seedlings were transplanted into the treated soil and their responses were observed until maturity. The data revealed that a highest concentration of Pb (1.2 mM) induced significant reduction in agronomic traits such as plant height, number of tillers per plant, number of panicles per plant, and number of spikelets per panicle in all the rice cultivars. However, least reduction in the agronomic traits was observed in X-Jigna, whereas the highest reduction in the agronomic traits was observed in Ediget. Antioxidant activity of catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO), and superoxide dismutase (SOD), was evaluated along with the accumulation of superoxide ions (O2.-), protein, proline, chlorophyll, sucrose, glucose, and fructose contents in all the rice cultivars. A significant increase in antioxidant activity and in the accumulation of proline and sucrose contents with the least reduction in the chlorophyll and protein contents was observed in X-Jigna suggesting that X-Jigna is the most tolerant among all the rice cultivars tested against Pb-stress. On the other hand, non-significant and slightly significant increase in the antioxidant activity, less accumulation of proline and sucrose contents, and higher reduction in the chlorophyll and protein contents was observed in Ediget, which further suggest that Ediget is the most susceptible rice cultivar to Pb-stress. In addition, the other rice cultivars Furat and Amber 33, were found to be moderately tolerant to Pb-induced oxidative stress. In summary, our results suggest that tolerance to Pb-induced oxidative stress would be a result of a synergetic action of both enzymatic and non-enzymatic antioxidant systems, leading to a balanced redox status in rice.

One-pot synthesis of spherical nanoscale zero-valent iron/biochar composites for efficient removal of Pb(ii).

In this study, a spherical Fe/C composite (AIBC) was successfully prepared via carbonization of Fe3+-crosslinked sodium alginate. The removal capacity and mechanism of AIBC were evaluated for the adsorption of Pb(ii) from aqueous solution and compared with that of commercial nanoscale zero-valent iron (nZVI). The effects of the initial concentration, pH of Pb(ii) solution, the contact time, coexisting anions, and aging under air were investigated. The results showed that the pH had a strong impact on the adsorption of Pb(ii) by AIBC. The adsorption data for AIBC followed the Langmuir model, while the maximum adsorption capacity at pH 5 was 1881.73 mg g−1. The AIBC had a higher adsorption capability than nZVI, especially under the condition of relatively high Pb(ii) concentrations. The oxidation–reduction reaction between Fe and Pb(ii) was the main mechanism for the adsorption of Pb(ii) onto nZVI. AIBC converted the largest amount of Pb(ii) into PbO·XH2O/Pb(OH)2 mainly by generating Fe2+.

Penentuan Kadar Selulosa Asetat pada Daun Tanaman Puring (Codiaeum variegatum) sebagai Penyerap Timbal di Udara

Pollution is one of the environmental problems in developing countries. Sources of pollution can be caused by nature and due to human actions. One of the air pollution sources is heavy metal content of Pb which is not easily decomposed in nature so that it can contaminate the environment. In Puring plants, especially the leaves have cellulose acetate which can filter heavy metals. The purpose of this study was the manufacturing of cellulose acetate from the leaves of the Puring plant. The cellulose obtained from the simplicia of leaves of the Puring plant will then be reacted into cellulose acetate through the acetylation reaction process using acetic anhydride with variations in temperature and reaction time taken, namely 40, 50, 60° C and as long as 50, 55, and 60 minutes. The levels of cellulose acetate were obtained through the cellulose extraction process, the synthesis of cellulose acetate and the final stage of making the membrane, from this process the optimum temperature and reaction time results were obtained in the second experiment with a temperature and reaction time of 50°C each and for 55 minutes without applying a catalyst 12.40%. In addition, the weight variation of raw material powder was taken, namely 20, 40, 60, 80, and 120 mg using a certain concentration of Pb (II) solution to determine the adsorbent capacity. These results can be obtained from analysis using Fourier Transform Infrared (FTIR).

Influence of Moderate Cd and Pb Soil Pollution on Seed Development, Photosynthetic Performance and Foliar Accumulation in the Medicinal Plant Hypericum perforatum

This study investigated whether moderate soil contamination by Cd and Pb may negatively affect seed germination, photosynthesis and foliar accumulation in the medicinal plant Hypericum perforatum. Seeds were incubated with Cd and Pb solutions of 10 and 100 µM, and two-month-old plants were watered weekly for three weeks with the same solutions. Control samples were treated with deionized water. The percentage of seed germination and seedling length, as well as chlorophyll content, chlorophyll fluorescence and foliar reflectance, were measured, along with the foliar Cd and Pb concentrations. The results indicated that seed germination is not affected, while seedling length is decreased by approximately 81% by high Cd levels. Cadmium was subjected to foliar translocation from the soil depending on the supplied concentration, thus causing reductions in the chlorophyll content (−24%). It is of interest that foliar Cd levels in Cd-treated plants were close to or above the limit for the European Pharmacopoeia. Negative effects of Pb were not detected, but accumulation and blockage of this metal at the root level, although not approached experimentally, cannot be ruled out.

Ion exchange properties of natural titanium silicate caryochroite (Na,Sr)3{(Fe,Mg)2+10(OH)6[TiO(Si6O17)(OH)0.5]2}·8H2O with a 1D system of parallel wide channels: Experimental study and theoretical analysis of the topochemical mechanisms

Ion-exchange properties of natural caryochroite (Na,Sr) 3 {(Fe,Mg) 2+ 10 (OH) 6 [TiO(Si 6 O 17 )(OH) 0.5 ] 2 }·8H 2 O, a microporous heterophyllosilicate with a one-dimensional system of broad zeolytic channels, related to nafertisite Na 3 {Fe 2+ 10 (OH) 6 [TiO(Si 6 O 17 )F 0.5 ] 2 }·2H 2 O, were studied in reactions with 1 N aqueous solutions of Rb, Cs, Ag, and Pb nitrates at 50 °C. In reactions with Rb + , Cs + , and Pb 2+ , sodium is partly replaced by nearly equivalent amounts of larger cations. In reactions with Pb 2+ and Ag + , additional processes involving H 2 O molecules take place: replacement of two H 2 O molecules with Pb 2+ + 2OH − and replacement of H 2 O molecule with Ag + + OH − , respectively. The geometrical-topological analysis of ion migration pathways in the nafertisite-type structures carried out using an approach based on the Voronoi-Dirichlet partition has shown that only Na + cations occurring at the centers of wide channels can take part in reactions with large alkaline cations proceeding in counter flows. In the reaction with Ag + , additional Na + ions are involved. Li + cations having a smaller radius can pass through the window between the channels, forming a 2D conducting layer. • Ion-exchange properties of natural titanosilicate caryochroite, a microporous heterophyllosilicate with a one-dimensional system of broad zeolytic channels, were studied in reactions with 1 N aqueous solutions of Rb, Cs, Ag, and Pb nitrates at 50 °C. • Three kinds of Na + cations in the caryochroite structure play different role in ion migration processes. • Li + cations having a smaller radius can pass through the window between the channels, forming a 2D conducting layer.

Metal free electrochemical glucose biosensor based on N-doped porous carbon material

An enzymatic metal-free electrochemical biosensor based on immobilized glucose oxidase on a N-doped porous carbon material has been studied for the detection of glucose in different real samples. The N-doped carbon material, which contains quaternary nitrogen groups, has been obtained by heat treatment of polyaniline. These functionalities promote the electrocatalytic activity to oxygen reduction reaction. The electrochemical biosensor presents a remarkable electrochemical activity towards oxygen reduction reaction, being able to detect changes in oxygen concentration generated by the enzymatic oxidation of glucose, allowing the indirect detection of this compound in phosphate buffered solution (0.1 M PB solution, pH=7.2). The metal-free electrochemical biosensor shows an outstanding performance, with a linear detection range between 5 µM and 5 mM and a high sensitivity of 23.57±1.77 µA mM−1 cm−2 at -0.4 V vs. Ag/AgCl. At these conditions, the addition of ascorbic acid, dopamine, uric acid and l-gluconic acid does not interfere with glucose determination. The method has been successfully applied to human urine and commercial sugary drink samples, without significant matrix effects, providing an alternative for glucose detection.

Synthesis of poly(ethyleneimine)-functionalized mesoporous silica gel with dual loading of host ion and crosslinking for enhanced heavy metal removal in multinary solutions

Polyethyleneimine (PEI)-functionalized mesoporous silica gel (SG) was synthesized through dual loading (d-PEI-SG) of copper (Cu) as a host ion for Cu(II)-PEI complex and crosslinking with glutaraldehyde in the synthesis pathway to enhance deposition of PEI on the SG. For comparison, the PEI-functionalized SG was also prepared through single loading (s-PEI-SG) of the host ion and crosslinking with glutaraldehyde. In thermogravimetric analysis, the weight loss of d-PEI-SG at 110–500 °C (7.8%) was greater than that of s-PEI-SG (2.8%), indicating the enhanced deposition of PEI on the silica gel surface of d-PEI-SG. The elemental composition from X-ray photoelectron spectroscopy analysis demonstrated that relative quantities of carbon and nitrogen in d-PEI-SG were larger than those of s-PEI-SG. In batch tests, the maximum Cu(II) adsorption capacity of d-PEI-SG was determined to 170.4 μmol g−1, which was four times larger than that (41.8 μmol g−1) of s-PEI-SG. In a multinary solution of divalent metal ions (Cu(II), Pb(II), Zn(II), Ni(II), and Co(II)) and trivalent/tetravalent metal ions (Cu(II), Al(III), Cr(III), and Zr(IV)), d-PEI-SG had a higher Cu(II) adsorption capacity and selectivity than s-PEI-SG. Column experiments were also conducted in the multinary solution of Cu(II), Pb(II), Zn(II), Ni(II), and Co(II), demonstrating that d-PEI-SG could remove more Cu(II) than s-PEI-SG in flow-through conditions.

Ion-exchange properties of the natural zeolite amicite

Crystals of the natural zeolite amicite, ideally K4Na4(Al8Si8O32)·10H2O, were ion-exchanged in the reactions with 0.1 N aqueous solutions of AgNO3, RbNO3, CsNO3 and Pb(NO3)2 at 363 K for 24 h. Under these conditions, Cs+ substitutes K+ whereas the most part of Na+ remains unexchanged; Rb+ partly substitutes both Na+ and K+; Pb2+ and Ag+ completely substitute Na+ and K+. All the compounds are monoclinic. The Cs- and Rb-substituted samples have unit-cell parameters close to those of initial amicite. The exchange of Na+ and K+ for Ag+ is accompanied by a significant decrease of the unit-cell volume. The unit-cell parameter c of Pb-amicite is nearly threefold larger than the c parameter of initial amicite. Infrared spectra show that framework topology is preserved during the ion exchange. The crystal structures of initial and Cs-exchanged amicites have been solved by direct methods.

Effects of Nano-Sized In2O3 on Sintering Behavior and Electrical Properties of 0.28Pb(In1/2Nb1/2)O3-0.40Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 Ceramics

0.28Pb(In1/2Nb1/2)O3-0.40Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 ceramics were synthesized by conventional solid-phase method using nano-sized In2O3. All the sintered 0.28PIN-0.40PMN-0.32PT ceramics have pure perovskite structure with composition locating at rhombohedral side around the morphotropic phase boundary (MPB) region. The 0.28PIN-0.40PMN-0.32PT ceramics belong to displacive driving ferroelectrics with apparent diffused phase transition characteristic. Although the rhombohedral-tetragonal ferroelectric phase transition temperature (TR-T) increases only to ∼120 °C due to the solid solution of Pb(In1/2Nb1/2) (PIN), the 0.28PIN-0.40PMN-0.32PT ceramics present high piezoelectric thermal stability till around the Curie temperature (Tm), which extremely widens the working temperature range and makes the 0.28PIN-0.40PMN-0.32PT ceramics suitable for high-temperature piezoelectric applications.

Quantification of toxic metals using machine learning techniques and spark emission spectroscopy.

The United States Environmental Protection Agency (US EPA) list of hazardous air pollutants (HAPs) includes toxic metal suspected or associated with development of cancer. Traditional techniques for detecting and quantifying toxic metals in the atmosphere are either not real time, hindering identification of sources, or limited by instrument costs. Spark emission spectroscopy is a promising and cost-effective technique that can be used for analyzing toxic metals in real time. Here, we have developed a cost-effective spark emission spectroscopy system to quantify the concentration of toxic metals targeted by the US EPA. Specifically, Cr, Cu, Ni, and Pb solutions were diluted and deposited on the ground electrode of the spark emission system. The least absolute shrinkage and selection operator (LASSO) was optimized and employed to detect useful features from the spark-generated plasma emissions. The optimized model was able to detect atomic emission lines along with other features to build a regression model that predicts the concentration of toxic metals from the observed spectra. The limits of detections (LODs) were estimated using the detected features and compared to the traditional single-feature approach. LASSO is capable of detecting highly sensitive features in the input spectrum; however, for some toxic metals the single-feature LOD marginally outperforms LASSO LOD. The combination of low-cost instruments with advanced machine learning techniques for data analysis could pave the path forward for data-driven solutions to costly measurements.

The potentials of Eichhornia crassipes for Pb, Cu, and Fe removal from polluted waters

Toxic metals are a major group of water pollutants that find their way into water bodies through municipal, industrial, and agricultural waste discharges. Phytoremediation of these metals has become popular because of the low-cost and environmental friendliness of the technique. Here, we evaluated the potential of Eichhornia crassipes (water hyacinth, WH) to remove lead (Pb), copper (Cu), and iron (Fe) from polluted waters. Five experimental prototypes (A–E) were developed for the phytoremediation. Prototypes A, B, C, and D contained 2 L of the underlay water spiked with 1, 2, 5, and 10 mL of Pb, Cu, and Fe stock solutions, respectively, whereas prototype E was the control (i.e., deionized water). About 200 g of live WH of the same rootstock was relocated into each prototype and exposed to the same environmental conditions. The concentrations of the metals were measured every three days for a 12-day remedial period. Also, the metal concentrations in the plant tissues (leaf, stem, and root) were monitored. We observed that in prototypes A and B, the WH achieved significant Cu, Pb, and Fe removal after 12 days. The removal efficiency (RE) of 45.81%, 19.29%, and 72.03% were achieved for Pb, Cu, and Fe, respectively in prototype A, whereas it was 25.63%, 10.69%, and 42.77% in prototype B. Generally, the order of removal followed the order Fe > Pb > Cu. Likewise, the metal contents found accumulated in the plant tissues followed the same order. The leaves of WH in prototypes C and D showed rapid wilting and final death by the 12th day. Consequently, phytoaccumulation was established because the metal concentrations were in the order: root > stem > leaves.

Sorption mechanisms of lead on soil-derived black carbon formed under varying cultivation systems

The knowledge about lead (Pb) sorption on soil-derived black carbons (SBCs) under different cultivation intensities of soils is limited. In this study, chemical and spectroscopic methods were applied to investigate the Pb sorption mechanisms on SBCs in soils from a forest land, a rubber plantation area, and a vegetable farm with none, less and highly intensive cultivation, respectively, that are located in the Hainan Island of China. Results showed that the specific surface area and cation exchange capacity of the SBCs from the less and highly intensive cultivation soils were 4.5- and 2.7-fold, and 1.3- and 1.8-fold higher compared to that of SBC from the no-cultivation soil, which subsequently enhanced the Pb sorption capacities of SBCs in iron exchange fraction. Ion exchange and hydrogen bonded Pb fractions together accounted for about 80% of total Pb sorbed on all SBCs at an externally added 1000 mg L−1 Pb solution concentration. The OC–O groups also played key roles in Pb sorption by forming complexes of OC–O–Pb–O and/or OC–O–Pb. Overall, SBCs in soils under all studied cultivation intensities showed high potential to sorb Pb (with the maximum absorbed Pb amount of 46.0–91.3 mg g−1), and increased Pb sorption capacities of the studied soils by 18.7–21.1 mg kg−1 in the stable fraction (complexation). Therefore, SBC might be a potential environment-friendly material to enhance the Pb immobilization capacity of soil.

Ethanol leaf extract of Psychotria microphylla rich in quercetin restores heavy metal induced redox imbalance in rats

Psychotria microphylla is a plant found in Africa and many parts of the world where the leaves are locally used in folk medicine for the treatment of toxicity related liver diseases. We investigated the antioxidant potentials of ethanol leaf extract of Psychotria microphylla (ELE-PM) in restoring hepatic redox dysregulations in rats exposed to heavy metals. HPLC was used in quantifying the bioactive compounds in ELE-PM. DPPH (1,1-diphenyl-2 picrylhydrazyl), FRAP (Ferric reducing antioxidant power) and NO (Nitric Oxide) assays were used for in vitro studies. The in vivo studies involved 30 rats randomly divided into 5 groups (n = 6). Group 1 received normal saline (2 mg/kg), group 2, 3, 4 and 5 received a combined solution of Pb(NO3)2 (11.25 mg/kg) and HgCl2 (0.4 mg/kg) respectively. After 7 days of heavy metal exposure, groups 3, 4 and 5 received a daily bolus administration of 200, 400 and 600 mg/kg body weight of EE-PM respectively through oral intubation for 28 days. HPLC quantification revealed a high amount of quercetin (27.43 ± 0.04 mg/100g), lower amounts of gallic acid (7.60 ± 0.06 mg/100g) and rutin (0.38 ± 0.009 mg/100g). Additionally, ELE-PM demonstrated strong inhibitory potentials against free radical scavenging activity generated in vitro. More interestingly, administration of ELE-PM significantly ameliorated hepatic redox dysregulations elicited by the exposure of the rats to heavy metals in a dose dependent pattern. ELE-PM is highly rich in flavonoid compound quercetin and perhaps this may be responsible for the strong antioxidant potentials exhibited in this investigation.

Attenuation of Heavy Metals from Runoff Using Coconut Husk Adsorbent in Porous Asphalt Pavement

In this study, a laboratory model of porous asphalt pavement was developed and tested to evaluate the performance of reducing heavy metals from the artificial stormwater runoff, which corresponded to the rainfall intensity of a subtropical monsoon climate like Bangladesh. In addition to the conventional pavement layers such as surface, base, sub-base and subgrade layers, three additional layers such as a heavy metal adsorbent layer made of locally available coconut husk, sand layer, and geotextiles were placed in the model. The pavement strength and the flow values were measured to confirm the ability of the pavement to sustain medium traffic load. Artificial stormwater was prepared by mixing standard solutions of Pb, Cr, Zn, and Cu with tap waters. Uniform artificial rainfall intensity of 0.3 L/min equivalent to a rainfall intensity of 200 mm/hour was used that infiltrated through the pavement cross section for nearly 2.50 hours. Comparing with the initial concentrations of artificial stormwater, the concentrations of heavy metals such as Pb, Cr, Zn, Cu were reduced up to 87%, 42%, 73%, and 46%, respectively below the coconut husk layer, which indicated the better ability of reducing heavy metal by surface and coconut husk layers. Overall, Pb, Cr, Zn and Cu in the bottom of the pavement layers were reduced by 89%, 56%, 98%, and 67%, respectively. So, the developed porous asphalt pavement can be adopted as an alternative to conventional pavement after further extensive in-situ investigation at various sites.

A Biosorption-Pyrolysis Process for Removal of Pb from Aqueous Solution and Subsequent Immobilization of Pb in the Char

The application of biosorption in the removal of heavy metals from water faces a challenge of safe disposal of contaminated biomass. In this study, a potential solution for this problem was proposed by using a biosorption-pyrolysis process featured by pretreatment of biomass with phosphoric acid (PA). The PA pretreatment of biomass increased the removal efficiency of heavy metal Pb from water by sorption, and subsequent pyrolysis helped immobilize Pb in the residual char. The results indicate that most (>95%) of the Pb adsorbed by the PA-pretreated biomass was retained in the char, and that the lower pyrolysis temperature (350 °C) is more favorable for Pb immobilization. In this way, the bioavailable Pb in the char was hardly detected, while the Pb leachable in acidic solution decreased to <3% of total Pb in the char. However, higher pyrolysis temperature (450 °C) is unfavorable for Pb immobilization, as both the leachable and bioavailable Pb increased to >28%. The reason should be related to the formation of elemental Pb and unstable Pb compounds during pyrolysis at 450 °C, according to the X-ray diffraction study.

Exploring of toxic Pb(II) removal by low-cost bio-adsorbent of camphor leaf forestry waste after camphor oil extraction.

Camphor leaf (CL) was widely used to extract camphor oil and thus led to abundant forestry waste. In order to reduce pollution, the waste CL was used to prepare bio-adsorbent for Pb(II) removal after alkali treatment and functional modification. The effects of solution pH, initial Pb(II) concentration, contact time and solution temperature were investigated on adsorption process to evaluate the potential application in heavy metal ions' removal. It was found that the massive hydroxyl groups released and plenty of micro-pores formed after the alkali treatment of CL bio-adsorbent, which obviously increased the Pb(II) adsorption. And the adsorption performance promoted continually after further functional modification by ionized 1,2,3,4-butanetetracarboxylic acid (BTCA). The increase of pH was favourable for the adsorption even though the precipitation effect was deducted. Linear fitting method was more suitable to describe the adsorption process than nonlinear fitting method, including adsorption isotherms and adsorption kinetics research. The adsorption thermodynamics was better to be described by nonlinear fitting method due to its lower root mean square error (RMSE) value and higher R2 value. Among which, the adsorption isotherm and adsorption kinetics were fitted well to Langmuir model and pseudo-second-order model, respectively. The adsorption thermodynamics was exothermic in nature and the process was spontaneous at low solution temperature. The adsorption mechanism was revealed as the combination of dominant chemical adsorption and assistant physical adsorption.

PET-microplastics as a vector for heavy metals in a simulated plant rhizosphere zone

Although microplastics (MPs) are ubiquitous contaminants in different ecosystems, their interactions with other pollutants including heavy metals remain relatively unknown. Wheat is an important grain that makes the basis of human food in many parts of the world. Thus, pollutants that affect its production are important subjects of study. This research focuses on the possible effects of the transport of the adsorbed heavy metals onto MPs to the roots of growing wheat. The adsorption of three heavy metals (Pb, Cd, and Zn) onto PET particles was examined. Pb and Cd were selected because they are known to be toxic, while Zn is an essential nutrient for plants. Adsorption experiments were performed using 1 g of PET-MP particles in 20 ml of five different concentrations of each individual element (Pb, Cd, and Zn) (denoted as S-elements). To investigate the antagonistic and synergistic effects of these elements on each other, they were studied collectively with all 3 elements present (denoted as C-elements). Desorption experiments were then performed for three scenarios in which the wheat rhizosphere zone was simulated. Generally, the concentration of the investigated heavy metals adsorption on polyethylene terephthalate (PET) decreased in the order: S-Cd > S-Zn > S-Pb and C-Zn > T-Cd > C-Pb. PET particles exposed to Zn, Cd, and Pb solution adsorbed from 7.2 to 8.5%, 5.3 to 9.8%, and 29.8 to 68.5% of the initial heavy metals concentration, respectively. 11.3 to 15.2%, 12.5 to 23.35%, and 5.5 to 33.6% of the initially adsorbed Zn, Cd, and Pb were desorbed in the wheat rhizosphere zone in the three defined scenarios, respectively. The results show that PET particles can act as a vector in transferring heavy metals to the rhizosphere zone.

Effective Removal of Pb(II) Ions by Electrospun PAN/Sago Lignin-based Activated Carbon Nanofibers.

Heavy metal pollution, such as lead, can cause contamination of water resources and harm human life. Many techniques have been explored and utilized to overcome this problem, with adsorption technology being the most common strategies for water treatment. In this study, carbon nanofibers, polyacrylonitrile (PAN)/sago lignin (SL) carbon nanofibers (PAN/SL CNF) and PAN/SL activated carbon nanofibers (PAN/SL ACNF), with a diameter approximately 300 nm, were produced by electrospinning blends of polyacrylonitrile and sago lignin followed by thermal and acid treatments and used as adsorbents for the removal of Pb(II) ions from aqueous solutions. The incorporation of biodegradable and renewable SL in PAN/SL blends fibers produces the CNF with a smaller diameter than PAN only but preserves the structure of CNF. The adsorption of Pb(II) ions on PAN/SL ACNF was three times higher than that of PAN/SL CNF. The enhanced removal was due to the nitric acid treatment that resulted in the formation of surface oxygenated functional groups that promoted the Pb(II) ions adsorption. The best-suited adsorption conditions that gave the highest percentage removal of 67%, with an adsorption capacity of 524 mg/g, were 40 mg of adsorbent dosage, 125 ppm of Pb(II) solution, pH 5, and a contact time of 240 min. The adsorption data fitted the Langmuir isotherm and the pseudo-second-order kinetic models, indicating that the adsorption is a monolayer, and is governed by the availability of the adsorption sites. With the adsorption capacity of 588 mg/g, determined via the Langmuir isotherm model, the study demonstrated the potential of PAN/SL ACNFs as the adsorbent for the removal of Pb(II) ions from aqueous solution.

INFLUENCE OF TEMPERATURE AND INTENSITIVITY OF MIXING ON TECHNICAL CHARACTERISTICS OF THE CHEMICALLY RECEIVED SUSPENSION OF PBCRO4

The expediency of applying the reagent method for wastewater treatment of industrial enterprises containing Cr6+ under conditions of real production using water-soluble salts of Pb2+ with the formation of a poorly soluble salt of PbCrO4 was used as a precipitating agent. The effect of temperature and mixing intensity on the chemical deposition of PbCrO4 in the H2CrO4-Pb(CH3COO)2-H2O system is studied. A solution of Н2CrО4 with a concentration of 100 mg/l (in terms of Cr (IV)), which models a typical wash water of the first stage of washing of the process of electrochemical chromium plating, was used as a starting material. An aqueous solution of lead oxalate saturated at 20°C was used as a precipitant (30,7 g/100 g of water). The precipitating solution was dosed once to chromium (VI) - containing solution, based on the following molar ratios: stoichiometric amount (100%) and an excess of 120 and 150% to form lead chromate. The temperature was maintained at the level of: 20, 30, 40, 50, and 60 °С, and the rotation speed of the mixer shaft was maintained at the levels: 0 (without mixing), 1.4; 2; 2.5 and 3 rpm. After dosing the precipitator solution, the resulting suspensions were kept under stirring and at the set temperature for 60 minutes and defended with a parallel sedimentation analysis. Studies have established that at a temperature of 20 ÷ 30 ° C and an excess of the precipitating reagent solution of 20 ÷ 50%, it is possible to obtain residual Cr6+ concentrations in purified solutions close to the MPC level. The most optimal mixing speed of suspensions is 1.5 ÷ 2 rpm. This mixing intensity helps to increase the separation rate of the resulting suspensions, allows one to obtain a PbCrO4 precipitate with particle sizes of 1.4–1.6 μm, and does not increase the residual Cr6+ concentration in purified solutions. With increasing excess of precipitant, the growth rate of PbCrO4 crystals decreases compared to the rate of nucleation. Thus, the feasibility of using an aqueous solution of Pb(CH3COO)2 as a precipitating reagent for the purification of Cr6+ -containing wastewater from electrochemical plants has been shown.