Pb Sorption Research Articles

Inventories, profiles and deposition fluxes of 210Pbex in mineral and organic (peatlands) Southern Hemisphere soils

Unsupported 210Pb (210Pbex) activity profiles have been determined in both mineral soils from Argentina (La Plata region) and organic soils from Brazil (Serra do Espinhaço Meridional). For the Argentine mineral soils, no significant differences in the 210Pbex inventories are found (ranging from 2920 ± 560 to 4570 ± 460 Bq/m2). The measured activity profiles are properly fitted by the one-dimensional transport model by effective diffusion and migration developed by He and Walling and the resulting parameters were analyzed considering the soil properties. It was observed that the migration rate is inversely proportional to the illite content, that the soils with higher amounts of smectite exhibit higher migration rates, and that the higher the pH, the higher the migration rate. These results agree with the higher Pb sorption capacity of smectite than illite, at identical conditions, and the Pb speciation with pH, that gives raise to different interactions between Pb and soil components. For organic soils, 210Pbex accumulates in superficial layers (5 cm depth) and the 210Pbex inventories (ranging from undetectable value to 5100 ± 200 Bq/m2) depend on the altitude of the sampling points. The activity values of 210Pbex and 137Cs (previously reported) are not significantly correlated, probably because the 137Cs fallout occurred more than 50 years ago, allowing the 137Cs profiles to develop. Finally, the deposit fluxes were determined for both regions studied and were incorporated into the global curve elaborated in previous works, contributing to a better definition of the general trend reported for the Southern Hemisphere.

Adsorptive Removal Behavior of Pb (II) and Cr (VI) Pollutants from an Aqueous Environment onto Polyaniline-Modified MIL100(Fe)

The present work introduces a new sorbent, so-called PANI/MIL100(Fe), for removing Pb (II) and Cr (VI) from wastewater. The successful preparation of PANI/MIL100(Fe) was verified via Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) characterizations. This adsorptive material showed a microporous structure with surface area magnitudes of up to 261.29 m2/g, a total pore volume of 0.2124 cm3/g, and a pore size distribution of around 1.2 nm. The maximum adsorption capacities of PANI/MIL100(Fe) for Cr (VI) (pH = 2) and Pb (II) (pH = 6) were obtained as 72.37 and 81.76 mg/g, respectively. The isotherm modeling assessments illustrated that the sorption of Pb (II) and Cr (VI) was consistent with the Sips model (R2 > 0.99), while the adsorption kinetics were suited to a pseudo-second-order model (R2 > 0.95). Thermodynamic studies of both metal ions demonstrated the spontaneous and endothermic nature of the process. The reusability of the PANI/MIL100(Fe) indicated promising adsorption properties for Pb (II) and Cr (VI) up to three cycles. Moreover, the XRD and FT-IR spectroscopy results after adsorption/desorption showed excellent stability of the adsorbent and physisorption mechanism, wherein electrons were exchanged between the PANI/MIL-100(Fe) and Pb (II) and Cr (VI). Finally, the findings suggested that PANI/MIL100(Fe) can be considered an efficient and environmentally friendly adsorbent to remove Pb (II) and Cr (VI) from wastewater.

Sorption of Cd(II), Cr(VI), Ni(II), and Pb(II) onto unmodified sludge from a pond treating woolen processing industry wastewater

Sorption of Cd(II), Cr(VI), Ni(II), and Pb(II) onto unmodified sludge from a pond treating woolen processing industry wastewater

Phosphorus modified graphitic carbon nitride activated by guanidine phosphate enables fast, efficient and selective immobilization of aquatic lead

With the assistance of preinstalled silica templates, polymeric graphitic carbon nitride with enhanced porosity suffers from complicated procedures and by-product wastes. Besides, it is still difficult to achieve the incorporation of phosphate groups with high contents on carbon-based materials (mostly < 1.0 at.% of P) via a one-step preparation since phosphate species on the surfaces of sorbents could complex heavy metals strongly from wastewaters. Given the porosity engineering of guanidine phosphate (GP) for carbonaceous materials, GP activated graphitic carbon nitrides (GPCNs) with developed surface area (4.2–4.8 fold of enhancement than inactivated one) and abundant phosphate groups (9.9–16.7 at.% of P) were fabricated via a one-step pyrolysis at 450, 500, and 550 °C. On this basis, the sorption of Pb(II) on GPCNs were studied under geochemical conditions including contact time, solution pH, ionic strength, humic acid concentration, interfering cations and anions, and temperature. GPCN pyrolyzed at 500 °C could capture Pb(II) rapidly (20.0 min) with superior maximum capacities (81.8–217.1 mg/g at pH 5.0, T 298 K), excellent selectivity coefficients (8.10–16.54) and favorable reusability (81.4% of capacity remained). The formation of minerals was dominant for the selectivity rather than ion exchange or surface coordination, etc. This work starts up the facile activation of carbon nitride with developed porosity and surface functionality to manage aquatic pollutants.

Characterization and sorption study of Zn2[FeAl]-CO3 layered double hydroxide for Cu(II) and Pb(II) removal

This study reports the synthesis of a ternary layered double hydroxide (LDH) from ZnII, FeIII, and AlIII (Zn2[FeAl]-CO3) for the efficient removal Cu(II) and Pb(II) from water samples. Herein, Zn2[FeAl]-CO3 was prepared by a co-precipitation method and characterized using X-ray powder diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, N2 adsorption-desorption isotherms and differential scanning calorimetry analysis. The characterization results ensured the formation of a mesoporous LDH with carbonate as the interlayer anion and the presence of Zn, Fe and Al on the surface with a MII/MIII molar ratio of about 1.82. The Cu(II) and Pb(II) sorption process has been thoroughly studied for different parameters. The kinetic data showed that the process is very fast and follows a pseudo-first-order model. In addition, both surface sorption and intraparticle diffusion contributed to the rate-limiting steps in the sorption system. The sorption isotherms were evaluated quantitatively with four different isotherm models. It was found that the Redlich-Peterson and Freundlich models showed better correlation with the experimental data. The thermodynamics study indicates the endothermic, disorder-increasing and spontaneous nature of the sorption process. In conclusion, these results suggest that the synthesized Zn2[FeAl]-CO3 is favorable and useful for the removal of the studied metal ions and the high sorption capacity makes it a promising candidate material for the removal of heavy metals from water.

Preliminary Adsorption Studies of Pb (II) With Gmelina Sawdust; Zn-Oxalic Acid (Zn-Oxa) and Cu-OXA MOFs

This work is about sorption of Pb (II) with using Gmelina sawdust; Zn-OXA and Cu-OXA MOFs. Gmelina sawdust biosorbent was prepared by carbonization and subsequently activated; whereas, the MOFs sorbents were prepared using slow evaporation method. These materials were characterised using FTIR. The analyses revealed principally the presence of carboxyl, carbonyl, hydroxyl, and amine functional groups in the biomaterials; then hydroxyl and carbonyl for the MOFs. There was decrement in the FTIR absorption values of hydroxyl and carbonyl of the oxalic acid as observed in the spectra of the MOFs; implying that oxalic acid bonded to the Zn and Cu ions via O-H and C=O groups in the MOFs. The trend of sorption Pb (II) by these products is: Cu-OXA MOF (57%); Zn-OXA MOF (95%); uncarbonised sawdust (97%); and carbonized sawdust (99%). The presence of different functional groups (i.e. as listed above) of the sawdust sorbents and the MOFs is the reason they performed well in terms of the Pb (II) adsorption. However, the sawdust products and Zn-OXA MOF are more effective for the lead (II) removal than the Cu-OXA MOF.

Spirulina platensis Immobilized Alginate Beads for Removal of Pb(II) from Aqueous Solutions.

Microalgae contain a diversity of functional groups that can be used as environmental adsorbents. Spirulina platensis is a blue-green microalga that comprises protein-N, which is advantageous for use in nitrogen-containing biomass as adsorbents. This study aimed to enhance the adsorption properties of alginate hydrogels by employing Spirulina platensis. Spirulina platensis was immobilized on sodium alginate (S.P@Ca-SA) via crosslinking. The results of field-emission scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy analyses of the N-containing functional groups indicated that Spirulina platensis was successfully immobilized on the alginate matrix. We evaluated the effects of pH, concentration, and contact time on Pb(II) adsorption by S.P@Ca-SA. The results demonstrated that S.P@Ca-SA could effectively eliminate Pb(II) at pH 5, reaching equilibrium within 6 h, and the maximum Pb(II) sorption capacity of S.P@Ca-SA was 87.9 mg/g. Our results indicated that S.P@Ca-SA fits well with the pseudo-second-order and Freundlich models. Compared with Spirulina platensis and blank alginate beads, S.P@Ca-SA exhibited an enhanced Pb(II) adsorption efficiency. The correlation implies that the amino groups act as adsorption sites facilitating the elimination of Pb(II).

СОРБЦИЯ КАДМИЯ И СВИНЦА ВЕЩЕСТВАМИ, ПЕРСПЕКТИВНЫМИ ДЛЯ СОЗДАНИЯ КОМПОЗИЦИОННЫХ ПРЕПАРАТОВ НА ОСНОВЕ ГЕКСАЦИАНОФЕРРАТОВ

The development of new drugs and feed additives to reduce the accumulation of anthropogenic and natural toxicants (heavy metals, radionuclides, mycotoxins, pesticides, etc.) in the body of farm animals and livestock products remains an urgent task. One of the ways to solve it is to create multifunctional products containing ferrocyanides (hexacyanoferrates) of transition metals as active substances. In medicine and veterinary medicine, enterosorbents based on compounds of this class are used as independent pharmacological agents, and in the form of composite preparations, which are obtained by fixing ferrocyanides on carrier substances of different origin and chemical composition. To study the possibility of using certain substances as carriers in the creation of new composite preparations and to assess their effect on the detoxification properties of ferrocyanides, the sorption efficiency of a number of mineral and organic substances with respect to Cd and Pb was studied. It was found that the background content of Cd and Pb in the tested substances does not exceed the maximum permissible levels of these toxicants in feed, feed additives and veterinary preparations. Under in vitro conditions, the biomass of the fungus Inonotus obliquus (chaga), the preparations ferrocin, bifezh and KhZh-90, zeolite tuff shivyrtuin, smectite dioctahedral, white soot and chitosan succinate have the greatest efficiency of Cd and Pb sorption (with respect to Cd – 50.4-89.0%, Pb – 58.3-95.1%). The combined presence of Cd and Pb reduces the sorption capacity of most of the tested substances by 1.6-63.6%.

Research on the adsorption of melamine for Cu(II) and Pb(II)

Melamine contains three aromatic nitrogen atoms and three free amino groups, which have great adsorption potential for heavy metallic ions in wastewater. The sorption performances of melamine for Cu(II) and Pb(II) ( They are denoted as Cu&Pb) were studied. Some major effects such as adsorption time, original concentration, and temperature on its adsorption performances were studied. The effects confirmed that melamine had true adsorption for Cu&Pb, and higher selectivity for the adsorption of Cu&Pb in a binary blended system. The adsorption amount of Pb(II) on melamine reached 4.91 mg/g at pH 5, adsorption equilibrium time of 12 h, and temperature of 55 °C, while the sorption amount of Cu(II) was only 2.70 mg/g, with a difference of about 1.8 times. The adsorption mechanism shows that the sorption of Cu&Pb on melamine follows the Lagergren quasi-second-order kinetic model. This result indicates that the mixture of Cu&Pb can be separated by stepwise processes from a binary mixed system.

Feedstock nitrogen content mediates maximum possible Pb sorption capacity of biochars.

The use of biochar for the adsorption of contaminants from soil and water has received considerable interest due to biochar's high surface area, negative charge, and resistance to degradation. However, a knowledge gap still exists concerning the optimum selection of feedstocks and pyrolysis temperatures to maximise sorption capacity for metals. In this study, biochars were produced from 4 different feedstock materials (hay, wheat straw, coco coir, and pine bark) at 10 pyrolysis temperatures ranging from 300 °C to 750 °C, at 50 °C intervals. Batch sorption experiments were conducted to determine the maximum Pb sorption capacity for each biochar using the Langmuir model. The sorption isotherms fit the Langmuir model well (generally R2 > 0.7). The Langmuir maximum sorption capacity increased with an increase in pyrolysis temperature, according to a sigmoidal relationship. A sigmoidal model was fit to the data to derive the theoretical maximum possible sorption capacity obtainable from a feedstock. We observed a positive correlation between the nitrogen content of the feedstock and the theoretical maximum possible sorption capacity obtainable from the feedstock. This relationship highlights the importance of nitrogen content in feedstock to create biochars with a high Pb sorption capacity. It is possible that cation-π interactions with heterocyclic N structures are the primary mechanism for the sorption of Pb to these biochars, and this warrants further investigation.

A Sulfonated All-Aromatic Polyamide for Heavy Metal Capture: A Model Study with Pb(II).

Polyelectrolytes are widely used in heavy metal removal, finding applications as coagulants and flocculants. We compare the heavy metal removal capability of a water-soluble sulfonated semirigid polyamide, poly(2,2'-disulfonyl-4,4'-benzidine isophthalamide) (PBDI), with that of a well-known random-coil polymer, poly(sodium 4-styrenesulfonate) (PSS). Using lead (Pb(II)) as a model contaminant, both polymers precipitate out from solution at ~500 mg/L Pb(II) in water. The ability to remove Pb(II) from water was quantified using adsorption isotherms and fitted with Langmuir and Freundlich adsorption models. The sorption of Pb(II) by PSS fit the Langmuir model with a high degree of correlation (0.976 R2), but the sorption of Pb(II) by PBDI could not be accurately predicted using the Langmuir or Freundlich model. The sorption of Pb(II) by PBDI and PSS was compared by normalizing sorption by the number of sulfonate groups of each polymer and the ion exchange capacity (IEC), found by titration. We find that PBDI removes a greater amount of Pb(II) per gram of sorbent compared to PSS, 410 mg/g vs 260 mg/g, respectively, which cannot be accounted for by differences in IEC or number of sulfonate groups. Our findings confirm that the positioning of the sulfonate groups and the rigidity of the polymer backbone play an important role in how Pb(II) coordinates to the polymer prior to precipitating out from solution.

Adaptive neuro-fuzzy inference system (ANFIS) and multiple linear regression (MLR) modelling of Cu, Cd, and Pb adsorption onto tropical soils

Soils interact in many ways with metal ions thereby modifying their mobility, phase distribution, plant availability, speciation, and so on. The most prominent of such interactions is sorption. In this study, we investigated the sorption of Pb, Cd, and Cu in five natural soils of Nigerian origin. A relatively sparsely used method of modelling soil-metal ion adsorption, i.e. adaptive neuro-fuzzy inference system (ANFIS), was applied comparatively with multiple linear regression (MLR) models. The isotherms were well described by Freundlich and Langmuir equations (R2 ≥ 0.95) and the kinetics by nonlinear two-stage kinetic model, TSKM (R2 ≥ 0.81). Based on the values delivered by the Langmuir equation, the maximum adsorption capacities (Qm*) were found to be in the ranges 10,000–20,000, 12,500–50,000, and 4929–35,037 µmol kg−1 for Cd, Cu, and Pb, respectively. The study revealed significant correlations between Qm* and routinely determined soil parameters such as soil organic carbon (Corg), cation exchange capacity (CEC), amorphous Fe and Mn oxides, and percentage clay content. These soil parameters, combined with operational variables (i.e. solution/soil pH, initial metal concentration (Co), and temperature), were used as input vectors in ANFIS and MLR models to predict the adsorption capacities (Qe) of the soil-metal ion systems. A total of 255 different ANFIS and 255 different MLR architectures/models were developed and compared based on three performance metrics: MAE (mean absolute error), RMSE (root mean square errors), and R2 (coefficient of determination). The best ANFIS returned MAEtest 0.134, RMSEtest 0.164, and R2test 0.76, while the best MLR returned MAEtest 0.158, RMSEtest 0.199, and R2test 0.66, indicating the predictive advantage of ANFIS over MLR. Thus, ANFIS can fairly accurately predict the adsorption capacity and/or distribution coefficient of a soil-metal ion system a priori. Nevertheless, more investigation is required to further confirm the robustness/generalisation of the proposed ANFIS.

Lead and cadmium removal with native yeast from coastal wetlands

Abstract Water bodies affected by heavy metals have been characterized in some natural ecosystems such as coastal wetlands in Peru. For this reason, in the present study, the determination of heavy metals lead (Pb), cadmium (Cd), and others was carried out in the water bodies of the Regional Conservation Area (RCA) Wetlands of Ventanilla using the Induction Coupled Plasma method. Water samples were collected at the six most critical stations for Pb and Cd, for the isolation of lead-tolerant microorganisms in 2022 with the aim of evaluating native microorganisms with removal potential of Pb and Cd. Yeasts such as Candida guilliermondii, Candida famata, Cryptococcus laurentii, Cryptococcus humicola, and Rhodotorula mucilaginosa with tolerance to high concentrations of Pb were isolated. The yeast with the best Pb tolerance result was Candida guilliermondii isolated from groundwater (piezometer sampling J1); Pb sorption was conducted with active yeast (living biomass), whereas both Pb and Cd sorption were conducted with inactive yeast (dead biomass). The results were compared with those of a reference standard yeast strain Saccharomyces cerevisiae: the native yeast proved to have optimum behavior for the process.

Estimation of sorption-desorption characteristics of biosorbent of Lantana camara leaves for removal of Pb (II) ions from wastewater.

This study points out the method regarding the removal of Pb (II) ions from water by treatment with Lantana camara leaves' biosorbent (LCLB). The sorption process was investigated by varying different parameters pH, contact time, adsorbent dose, initial metal ion concentration, and temperature. For a 5.00g sorbent dose and a 45min of the contact period, a Pb (II) ion solution with an initial metal ion concentration of 10mg/L resulted in 90.7% maximum elimination at an optimum pH 6 and temperature 298 ± 1.5K with LCLB. The adsorption process was spontaneous and exothermic. The maximum monolayer adsorption was 3.5mg/g for Pb (II) sorption using LCLB. Adsorption of Pb (II) ions using LCLB (R2 > 0.999) followed the pseudo-second-order kinetics. The spectroscopic characterization was done byfourier transform infrared (FT-IR) analysis, while scanning electron microscope (SEM) images were captured for the morphological characterization. Desorption experiments revealed that hydrochloric acid has a strong potential as an eluent for Pb (II) ion desorption. The findings proposed that LCLB can be used as an effectual and cost-effective biosorbent for the expulsion of Pb (II) ions.

High-efficiency control of pesticide and heavy metal combined pollution in paddy soil using biochar/g-C3N4 photoresponsive soil remediation agent

The control of pesticide and heavy metal combined pollution in the paddy field is of great significance in terms of controlling agriculture nonpoint source pollution. Herein, an alkali-modified biochar (BCNaOH)/graphitic carbon nitride (g-C3N4) photoresponsive soil remediation agent was synthesized to control the pesticide and heavy metal compound pollution in paddy fields. Compared with g-C3N4, the photocurrent density increased 2.72 times for BCNaOH/g-C3N4, exhibiting a strong photocatalytic activity. In the simulated compound pollutant solution, the simultaneous Atrazine (ATZ) degradation and Pb sorption efficiencies of BCNaOH/g-C3N4 reached 94.70 % and 47.75 % under visible light irradiation, respectively. In the paddy field, both ATZ and Pb concentrations were well controlled in the overburden water and paddy soil. ATZ and Pb in overburden water reached 0 mg/L and 0.24 μg/L, respectively, and in paddy soil decreased by 60.21 % and 65.49 %, respectively. Excellent ATZ degradation performance was due to the construction of an intact photogenerated electron transfer pathway via the π-π stacking structure. Meanwhile, excellent Pb removal performance was due to the strong sorption capability of BCNaOH. The results provided a cost-effective photoresponsive soil remediation agent with good pesticide and heavy metal combined pollution control performance for paddy fields.

The influence of Pb(II) adsorption on (Non) biodegradable microplastics by UV/O3 oxidation treatment

Widely distributed in the natural environment, microplastics (MPs) may serve as carriers for adsorbing and carrying heavy metal. More research is still required to understand the aging process of MPs and interactions between MPs and heavy metals. In this study, we are going to explore the effects of UV/O3 oxidation on the adsorption behavior of Pb(II) on MPs. The MPs that we include in our study are conventional MPs (PE, polyethylene) and biodegradable MPs (PLA, polylactic acid). The results showed that the UV/O3 oxidation significantly increased its specific surface area and oxygen content, thereby enhancing the adsorption capacity of Pb(II) on MPs. Further, the physicochemical properties of PLA are changed much more than PE after UV/O3 oxidation. In this study, the adsorption process conformed to the pseudo-second-order kinetic and the intraparticle diffusion models, and the adsorption order was aged PLA > aged PE > original PLA > original PE. Their maximum adsorption capacities were 0.98 mg/g, 0.83 mg/g, 0.67 mg/g and 0.54 mg/g, respectively. Studies have implied that the oxidation degree and types of MPs have an impact on their interactions with co-existing pollutants. Overall, These studies indicate that oxidation treatment can alter the structural properties of microplastics while also revealing the Pb(II) sorption kinetics and mechanisms onto the MPs, which will help researchers better understand how MPs interact with heavy metals.

Sorption and post-sorption performances of Cd, Pb and Zn onto peat, compost and biochar

The development of waste-derived sorbents to immobilize potentially toxic elements (PTEs) is a promising strategy, contributing to the achievement of sustainable development goals (SDGs). Therefore, this study aimed to assess the sorption performance of cadmium (Cd), lead (Pb) and zinc (Zn), comparing sorbents derived from organic fraction of municipal solid waste (composts and biochars) with peat. The physicochemical characterization, equilibrium of sorption, post-sorption analyzes and bioaccessibility were investigated. Results showed that the sorbents have distinct characteristics; however, each material have their particularities favorable to sorption. For instance, peat and composts have the highest cation exchange capacity (800–1100 mmolc kg−1), while biochar produced at 700 °C has the highest specific surface area (91.21 m2 g−1). The sorption equilibrium data revealed the actual sorption capacity and was well explained by the Freundlich and Langmuir isotherms and, in some cases, by the Dubinin-Radushkevich model. Post-sorption analyzes indicated the occurrence of several sorption mechanisms, driven by the physicochemical properties. Electrostatic interaction stood out for peat and compost. The FTIR spectrum for peat proved the complexation with oxygenated functional groups. The composts showed variations in the released cations (e.g. Ca2+ and K+), indicating cation exchange. Differently, for biochars, the XRD patterns showed that precipitation or coprecipitation seems to be one of the main mechanisms, especially for Cd and Pb. Regarding human bioaccessibility, the results of the gastric phase simulation (pH∼1.20) revealed lower percentages of Pb (33–81%) than Cd (91–99%) or Zn (82–99%), especially for the highest concentrations. Nevertheless, in numerical terms, all bioaccessible concentrations inspire care. In conclusion, among the sorbents, composts and biochars presented the best sorption performances and, therefore, have great potential for environmental applications. Furthermore, the bioaccessibility findings indicate that these assays, still little used in experiments with sorbents, are an important tool that should be better explored in the assessment of the environmental risk associated with contamination.

Influence of soil properties on the development of bacterial community tolerance to Cu, Ni, Pb and Zn

Pollution-Induced Community Tolerance (PICT) is a helpful and sensitive methodology to evaluate the effect of metal pollution in soils using microorganisms as indicators. PICT was used to determine the increase of bacterial community tolerance to Cu, Ni, Pb and Zn (Δlog IC50), and to assess the influence of soil properties on the development of bacterial community tolerance to Cu, Ni, Pb, and Zn. Soil samples showed a wide range of properties, such as pH (3.96–7.47), texture (13.8–31.7% clay) or organic matter (9.7–30.7%). Bacterial growth measured by the [3H]-leucine incorporation method was used as the PICT endpoint. Bacterial communities generally developed tolerance in response to Cu, Ni and Zn additions to soils. However, bacterial communities showed no tolerance to Pb, probably due to high Pb sorption in studied soils. Soil properties influenced the development of bacterial community tolerance to Cu, Ni and Zn. Effective cation exchange and a soil sorption parameter (Freundlich's linearity index) were the selected variables to estimate Δlog IC50 to Cu (R2 = 0.65). Clay content and Ni-soluble are the main factors to estimate Δlog IC50 to Ni (R2 = 0.63). Organic matter content and a sorption parameter (maximum sorption capacity of the soil from Langmuir equation) are the soil properties to estimate Δlog IC50 to Zn (R2 = 0.45). Most of the variables exerted their effect in soil, i.e. PICT selection phase. However, clay content affected bacterial community tolerance determination (PICT detection phase), leading to overestimated measurements of bacterial community tolerance.

Effect of Pyrolysis Temperature on Removal Efficiency and Mechanisms of Hg(II), Cd(II), and Pb (II) by Maize Straw Biochar

Pyrolysis temperature significantly affects the properties of biochar, which in turn can affect the removal of heavy metal ions and the underlying mechanism. In this work, biochars from the pyrolysis of maize straw at 300, 400, and 500 °C (BC300, BC400, and BC500, respectively) and wheat straw at 400 °C (WBC400) were investigated. The influence of production temperature on the adsorption of Hg2+, Cd2+, and Pb2+ by maize straw biochar was investigated by the characterization of the biochars and by adsorption tests. The adsorption capacities of maize and wheat straw biochar were compared in an adsorption experiment. Biochar BC400 showed the best physical and chemical properties and had the largest number of surface functional groups. The pseudo-second-order kinetic model was more suitable for describing the adsorption behavior of metal ions to biochar. The Langmuir model better fit the experimental data. Biochar BC400 had a higher adsorption speed and a stronger adsorption capacity than WBC400. The sorption of Pb2+ and Hg2+ to maize straw biochar followed the mechanisms of surface precipitation of carbonates and phosphates and complexation with oxygenated functional groups and delocalized π electrons. The adsorption mechanism for Cd2+ was similar to those of Hg2+ and Pb2+, but precipitation mainly occurred through the formation of phosphate. In the multi-heavy-metal system, the adsorption of Cd2+ by BC400 was inhibited by Pb2+ and Hg2+. In summary, BC400 biochar was most suitable for the adsorption effect of heavy metals in aqueous solution.

A comparative and modeled approach for three biochar materials in simultaneously preventing the migration and reducing the bioaccessibility of heavy metals in soil: Revealing immobilization mechanisms

The effectiveness and feasibility of the three biochar materials for remediation of arsenic (As) and lead (Pb) contaminated soil were explored in this study. Significant reduction of bioaccessibility and migration risks of both heavy metals have been explained mechanistically by incubation, column experiments and numerical simulation. Langmuir equation fitted As and Pb sorption isotherms better in the control and biochar (BC) amended soils, while Freundlich model was more suitable for iron modified biochar (Fe-BC) and sulfur/iron modified biochar (S/Fe-BC) amended soils, indicating that modified biochar promoted chemical adsorption process for As and Pb. For the three biochar materials, S/Fe-BC showed the best effects on reducing the bioavailability of As and Pb, with a decrease of 40.42%–64.21%. The reduction in bioaccessibility by metal portioning into available and non-available fractions was better for illustrating the mechanisms including adsorption, precipitation/coprecipitation and As(III) oxidation behind S/Fe-BC efficacy. Moreover, S/Fe-BC can effectively inhibit the leaching behavior of As and Pb under acid rain, which increased by 99.89% and 90.18%, respectively, compared with the control. The HYDRUS-1D modeling indicated that S/Fe-BC could continuously treat As (100 mg/L) and Pb (1000 mg/L) contaminated water for 16.22 years and 40.86 years, respectively, and ensure the groundwater quality criteria being met. Based on these insights, we believe that our study will provide meaningful information about the potentials of biochar derived materials for soil heavy metals’ remediation.