Mechanism Of Pb Removal Research Articles

Removal mechanism of Pb(ii) from soil by biochar-supported nanoscale zero-valent iron composite materials

Removal mechanism of Pb(<scp>ii</scp>) from soil by biochar-supported nanoscale zero-valent iron composite materials

Valorisation of spent tire rubber as carbon adsorbents for Pb(II) and W(VI) in the framework of a Circular Economy

Spent tire rubber-derived chars and their corresponding H3PO4 and CO2-activated chars were used as adsorbents in the recovery of Pb(II) ion and (W(VI)) oxyanion from synthetic solutions. The developed chars (both raw and activated) were thoroughly characterized to have insight about their textural and surface chemistry properties. H3PO4-activated chars presented lower surface areas than the raw chars and an acidic surface chemistry which affected the performance of these samples as they showed the lowest removals of the metallic ions. On the other hand, CO2-activated chars presented increased surface areas and increased mineral content compared to the raw chars, having presented higher uptake capacities for both Pb(II) (103–116 mg/g) and W(VI) (27–31 mg/g) ions. Cation exchange with Ca, Mg and Zn ions was appointed as a mechanism for Pb removal, as well as surface precipitation in the form of hydrocerussite (Pb3(CO3)2(OH)2). W(VI) adsorption might have been ruled by strong electrostatic attractions between the negatively charged tungstate species and the highly positively charged carbons’ surface.The results shown in this work allow concluding that the valorisation of spent tire rubber through pyrolysis and the subsequent activation of the obtained chars is an alternative and a feasible option to generate adsorbent materials with a high uptake capacity of critical metallic elements.

A novel bio-washing eluent obtained from fermentation of fruit wastes for removal of soil Pb: efficiency, mechanism, and risk assessment.

Agricultural wastes are inexpensive materials for soil remediation. However, the direct water extracts from these wastes showed low efficiency for Pb removal, thus limiting their application. In this study, citrus pericarp (CP) and pineapple peel (PP), as the common agricultural wastes, were inoculated with lactic acid bacteria to produce fermentation liquors (FCP and FPP) for improving Pb removal efficiency. Results showed that the Pb removal rates by FCP and FPP reached 37.3 and 43.6%, and increased by almost 50.0% than those by CP and PP. The ecological risk of Pb reduced by 83.0-88.2% after five times continuous washing with FCP and FPP, and the Pb concentrations conformed to soil remediation standard of China. Moreover, soil organic carbon 1.5 times increased in the washed soils, while total potassium improved by 40.7-68.0%. The mechanisms of Pb removal by these wastes involved in adsorption-desorption of Pb2+, complexation with organic ligands, and co-precipitation of Pb complexes. The increase of low molecular organic acids during the fermentation promoted dissolution of Pb and provided more hydroxyl, carboxyl, and amine groups to interact with Pb2+, thus improving its removal rate. Therefore, fermentation liquid from fruit wastes is a novel, effective, and ecofriendly bio-washing eluent for Pb removal from contaminated soils.

Adsorption and removal mechanism of Pb(II) by oxidized multi-walled carbon nanotubes

Adsorption and removal mechanism of Pb(II) by oxidized multi-walled carbon nanotubes

Preparation of Mixed Metal Oxide/Carbon Composites and Its Adsorption Performance for Pb(Ⅱ)

Layered double hydroxides, which can be synthesized from metal ions and their analogs, have abundant interlayer ions, surface functional groups, and adsorption characteristics that have been extensively studied. But the adsorption-desorption process may cause secondary pollution of the environment. In this study, the layered double hydroxides that adsorbed Congo red were converted into mixed metal oxide/carbon composites by a calcining carbonization method, and its adsorption performance for heavy metal ions Pb(Ⅱ) in aqueous solution was studied in detail. The results show that the prepared mixed metal oxide/carbon composites have a faster adsorption rate and higher adsorption capacity for Pb(Ⅱ). The adsorption capacity reached more than 150 mg·g-1 in 30 min, and increased with the content of Mg2+ introduced into the layered double metal hydroxide, reaching a maximum of 368 mg·g-1. The removal mechanism of Pb(Ⅱ) by mixed metal oxide/carbon composites was caused by the formation of insoluble Pb3(CO3) 2(OH) 2 on the surface. This research lays the foundation for the application of mixed metal oxide/carbon composites in the remediation of lead-containing soils.

Removal mechanism of Pb(II) by Penicillium polonicum: immobilization, adsorption, and bioaccumulation

Currently, lead (Pb) has become a severe environmental pollutant and fungi hold a promising potential for the remediation of Pb-containing wastewater. The present study showed that Penicillium polonicum was able to tolerate 4 mmol/L Pb(II), and remove 90.3% of them in 12 days through three mechanisms: extracellular immobilization, cell wall adsorption, and intracellular bioaccumulation. In this paper. the three mechanisms were studied by Raman, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The results indicated that Pb(II) was immobilized as lead oxalate outside the fungal cell, bound with phosphate, nitro, halide, hydroxyl, amino, and carboxyl groups on the cell wall, precipitated as pyromorphite [Pb5(PO4)3Cl] on the cell wall, and reduced to Pb(0) inside the cell. These combined results provide a basis for additionally understanding the mechanisms of Pb(II) removal by P. polonicum and developing remediation strategies using this fungus for lead-polluted water.

Sulfidation enhanced reduction of polybrominated diphenyl ether and Pb(II) combined pollutants by nanoscale zerovalent iron: Competitive reaction between pollutants and electronic transmission mechanism

Sulfidated nanoscale zerovalent iron (S-nZVI) has showed higher reactivity towards organic pollutants and metal ions than nZVI. However, the competitive reaction and electron transport mechanism of organic-metal ions with S-nZVI in one-pot need further clarification. In this study, the removal mechanism of Pb(II) and decabromodiphenyl ether (BDE-209) complex contaminants by S-nZVI was systematically investigated. Compared with nZVI, the removal kinetic constants of BDE-209 and Pb(II) by S-nZVI (S/Fe ratio = 0.2) increased 7.29 and 5.15 times, respectively. Pb(II) can be immobilized to PbO, Pb0 and PbS by S-nZVI particles via various surface reactions as electrostatic adsorption, reduction reaction and co-precipitation process. The removal efficiencies of Pb(II) by S-nZVI did not change significantly with increasing BDE-209 concentration. But in low S-nZVI dosage system, S-nZVI could preferentially react with Pb(II) due to the stronger electrostatic adsorption between S-nZVI and Pb(II) than that of S-nZVI and BDE-209. It was the formation of a galvanic effect of Pb0 with Fe0 on S-nZVI surface rather than active hydrogen atom (H) that enhanced the reductive rate of BDE-209 in the presence of Pb(II). Sulfidation could inhibit the passivation and corrosion process by water/dissolved oxygen and improve the storage time and lifetime of nZVI. Whereas, the presence of Pb(II) accelerated the corrosion of S-nZVI during the aged reaction even without BDE-209, which adversely affected the longevity of S-nZVI. The dual effects of Pb(II) on the treatment of compound pollutants of BDE-209 and metal ions by S-nZVI should be taken into account in real application.

The effects of different factors on the removal mechanism of Pb(ii) by biochar-supported carbon nanotube composites.

Herein, biochar-supported nanomaterials were synthesized using a mixture of chestnut shells and carbon nanotubes via slow pyrolysis at 600 °C for 1 h. Then, the adsorption ability of chestnut shell-carbon nanotubes (CS-CNTs) towards the removal of aqueous Pb(ii) was tested. The removal capacity of Pb(ii) by CS-CNT was 1641 mg g−1, which was significantly higher than that by the biochar of chestnut shells (CSs) (1568 mg g−1), which demonstrated that the sorption capacity could be improved by the carbon nanotubes. The factors studied here indicated that the adsorption was rapid in the initial 15 min under the conditions of the Pb(ii) concentration of 50 mg L−1 and the pH value of 5, and the values reached 1417 mg g−1 and 1584 mg g−1. The adsorption rate and capacity increased on increasing the concentration of NaCl. The sorption reaction was consistent with the Langmuir model, indicating a mono-layer adsorption behavior. The adsorption process can also be defined via the pseudo-second-order model, suggesting that the adsorption of Pb(ii) might be controlled by chemisorption. After carrying out four cycles of adsorption–desorption experiments, the adsorption rates of CS and CS-CNT remained at 82.92% and 88.91%, respectively, indicating that the biochar samples had stable and excellent sorption ability for heavy metals and huge application value. Thus, this study would provide a promising sorbent for the treatment and remediation of metal contaminants.

Mechanism of Pb Removal from Brass Scrap by Compound Separation Using Ca and NaF

The Mechanism of Pb removal from brass scrap by compound separation using Ca and NaF addition was investigated. Because large Ca-Pb compound particles formed by Ca addition rise to the surface of the molten brass, they can be skimmed off from the molten brass. However, fine Ca-Pb compound particles remain in the molten brass because of low buoyancy. By subsequent NaF addition, the reaction between Ca-Pb compound and NaF takes place at their contact regions, resulting in the formation of solid CaF2, liquid Pb and Na gas. Pb is mainly present at the Ca-Pb compound-CaF2 interface. CaF2 acts as a binder for aggregation of fine Ca-Pb compound particles, resulting in the formation of light and large composite compounds, which rise to the surface of the molten brass. A high Pb removal rate is achieved by skimming off.

Simultaneous and continuous stabilization of As and Pb in contaminated solution and soil by a ferrihydrite-gypsum sorbent

For the increasing need of stabilization both cationic and anionic metal(loid)s simultaneously, we newly developed a metal sorbent (FIXALL), consisting mainly of ferrihydrite and gypsum. The objectives of this study were to determine the molecular mechanisms of Pb and As stabilization in an aqueous system and to examine a simultaneous and long-term (up to 754days) effect on Pb and As stabilization in an anthropogenically contaminated soil using the FIXALL sorbent. When the solution contained a low concentration of Pb (5mgL−1), the mechanisms of Pb removal by FIXALL were based chiefly on the formation of inner-sphere surface complex with ferrihydrite. In the highly concentrated Pb solution (1200mgL−1), contrarily, the removal of Pb by FIXALL was the direct consequence of the dissolution of gypsum and subsequent precipitation of PbSO4, which strengthens the drawback of low capability of ferrihydrite for Pb removal. Regardless of initial concentrations, the primary mechanism of FIXALL for As stabilization is attributed to the formation of inner-sphere surface complex with ferrihydrite. A contaminated soil study demonstrated that FIXALL could decrease the concentration of water soluble As and Pb simultaneously and continuously for 754days without notable changes in their chemical species and soil pH.

Nano-Structured Magnesium Oxide Coated Iron Ore: Its Application to the Remediation of Wastewater Containing Lead.

Magnetically separable nano-structured magnesium oxide coated iron ore (IO(MgO)) was prepared using environmentally benign chemicals, such as iron ore (IO), magnesium(II) nitrate hexahydrate [Mg(NO3)2 x 6H2O] and urea; via an easy and fast preparation method. The lO(MgO) was characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) and alternating gradient magnetometer (AGM) analyses. The isotherm and kinetic studies indicated that lO(MgO) has a comparably higher Langmuir constant (K(L), 1.69 L mg(-1)) and maximum sorption capacity (33.9 mg g(-1)) for lead (Pb) than other inorganic media. Based on MgO amount, the removal capacity of Pb by IO(MgO) was 2,724 mg Pb (g MgO)(-1), which was higher than that (1,980 mg g(-1)) for flowerlike magnesium oxide nanostructures reported by Cao et al. The kinetics, FE-SEM, elemental mapping and XRD results revealed that the substitution followed by precipitation was identified as the mechanism of Pb removal and plumbophyllite (Pb2Si4O10 x H2O) was the precipitated phase of Pb. A leaching test revealed that IOMgO) had negligible concentrations of leached Fe at pH 4-9. Since the base material, IO, is cheap and easily available, lO(MgO) could be produced in massive amounts and used for remediation of wastewater containing heavy metals, applying simple and fast magnetic separation.

Removal of lead(II) and copper(II) from aqueous solution using foitite from Linshou mine in Hebei, China

Foitite from Linshou mine in China's Hebei province was investigated as an adsorbent to remove Pb(II) and Cu(II) from aqueous solution. The results showed that foitite can readily remove heavy metal ions from aqueous solution. The data shows that the metal uptake for Pb(II) increases rapidly, accounting for 74.47% when contact time was 2 min. In contrast to Pb(ll), there was a worse capability for adsorption of Cu(II). In the first 4 min, the metal uptake accounted for 34.7%. According to the analytical results obtained from X-ray diffraction, laser Raman spectrum, X-ray energy dispersive spectrometer, and Zeta potential, the removal mechanism of Pb(II) and Cu(II) by using foitite can be explained as following: firstly, the existence of an electrostatic field around foitite particles can attract heavy metal ions and consequently combine heavy metal ions with OH; secondly, heavy metal ions in the solution are exchanged with the Fe3+ and Al3+ in the foitite.

Preparation and lead ion removal property of hydroxyapatite/polyacrylamide composite hydrogels

We report the synthesis of hydroxyapatite/polyacrylamide (HAp/PAAm) composite hydrogels with various HAp contents by free radical polymerization and their removal capability of Pb 2+ ions in aqueous solutions with controlled initial Pb 2+ ion concentrations and pH values of 2–5. The swelling ratio of the composite gels in aqueous solutions decreases with increasing the HAp content in the gels. The composite gel with higher HAp content exhibits the higher removal capacity of Pb 2+ ions owing to the higher adsorption sites for Pb 2+ ions, but shows the slower removal rate of Pb 2+ ions due to the lower degree of swelling. The removal mechanism of Pb 2+ ion is very sensitive to the pH value in aqueous solution, although the removed amount of Pb 2+ ion is nearly same, regardless of pH values of 2–5. The removal mechanism, the dissolution of HAp in the composite gel and subsequent precipitation of hydroxypyromorphite (HPy), is dominant at lower pH 2–3, whereas the mechanism, the adsorption of Pb 2+ ions on the composite gel and following cation exchange reaction between Pb 2+ ions adsorbed and Ca 2+ of HAp, is dominant at higher pH 4–5. The equilibrium removal process of Pb 2+ ions by the composite gels at pH 5 is described well with the Langmuir isotherm model. The equilibrium removal capacities of the composite gels with 30, 50, and 70 wt.% HAp contents are evaluated to be 123, 178, and 209 mg/g, respectively.

Removal of lead ions in aqueous solution by hydroxyapatite/polyurethane composite foams

We have prepared hydroxyapatite/polyurehthane (HAp/PU) composite foams with two different HAp contents of 20 and 50 wt.% and investigated their removal capability of Pb 2+ ions from aqueous solutions with various initial Pb 2+ ion concentrations and pH values of 2–6. HAp/PU composite foams synthesized exhibited well-developed open pore structures which provide paths for the aqueous solution and adsorption sites for Pb 2+ ions. With increasing the HAp content in the composites, the removal capability of Pb 2+ ions by the composite foams increases owing to the higher adsorption capacity, whereas the removal rate is slower due to the less uniform dispersity of HAp in composite foams. The removal rate of Pb 2+ ions is also slower with increasing the initial Pb 2+ ion concentration in aqueous solutions. The removal mechanism of Pb 2+ ion by the composites is varied, depending on the pH value of aqueous solution: the dissolution of HAp and precipitation of hydroypyromorphite is dominant at lower pH 2–3, the adsorption of Pb 2+ ions on the HAp/PU composite surface and ion exchange reaction between Ca 2+ of HAp and Pb 2+ in aqueous solution is dominant at higher pH 5–6, and two removal mechanisms compete at pH 4. The equilibrium removal process of Pb 2+ ions by the HAp/PU composite foam at pH 5 was described well with the Langmuir isotherm model, resulting in the maximum adsorption capacity of 150 mg/g for the composite foam with 50 wt.% HAp content.