Heavy Metal Adsorption Process Research Articles

Investigating the distribution of microplastics in soils from e-waste dismantling sites and their adsorption of heavy metals.

Microplastics are characterized by strong hydrophobicity, large specific surface area. In addition to the pollutant they contain, the heavy metals adsorbed on the surface of microplastics can migrate or be transformed with them into the environmental medium, which is potentially harmful to humans. The distribution characteristics of microplastics in contaminated soil at the e-waste dismantling site were studied. The study investigated the adsorption characteristics of polyvinyl chloride (PVC), polypropylene (PP) and acrylonitrile-butadiene-styrene (ABS) on copper (Cu), zinc (Zn) and lead (Pb). It analysed the influence of various factors on the adsorption process of heavy metals, the adsorption law of microplastics on some of the heavy metals in the environment, and the risk of heavy metal release from microplastics to soil. The results showed that ABS and PP were the main microplastics in the contaminated soil. Among them, black, white and transparent microplastics accounted for 89.91%. The shape of microplastics is mainly granular, and microplastics with a particle size of 1-2 mm accounted for the largest proportion. Further studies showed that plastic particles made of ABS, PP and PVC also have the adsorption capacity for different types of heavy metals in soil, and the trends of adsorption capacity are: PP>PVC>ABS. When PP does not reach adsorption equilibrium in the adsorption process, the smaller the particle size and the more added amount, the greater the adsorption capacity. This is because the smaller the particle size of the microplastic is, the more adsorption points it can provide, increasing its ability to adsorb heavy metal ions.

Electrospun membranes with magnetite NPS for potential use of heavy metals ion adsorption

Water contamination by heavy metal ions is a current problem that affects human health and occurs mainly due to anthropogenic activities. One of the main mechanisms for water decontamination is the use of magnetic adsorbent materials, because it is a method of easy implementation, low cost and easy recovery, with the use of an external magnetic field. In this study, an electrospun polymeric membrane of PVDF-PS with magnetite (Fe3O4) nanoparticles was successfully fabricated. The morphological characterization of the membrane with SEM showed that the fibers reach a diameter of around 2.5 µm, increasing the contact surface area for the adsorption of heavy metal ions. The magnetic nature of the electrospun membrane is calculated with a vibrating sample magnetometer (VSM), which shows that the material is superparamagnetic in nature due to the incorporation of magnetite nanoparticles. These characteristics of adsorbent materials are relevant for potential use in heavy metal adsorption processes.

Detailed insights in adsorption process of heavy metals on tire wear particles

Road traffic induced tire wear particles (TWP) attracted widespread attention due to their potential environmental impact. Here, the adsorption process of heavy metals like Pb2+ and Cd2+ on tire wear particles produced by filing (TWP-f) is studied to elucidate the underlying kinetics and thermodynamics. This work includes voltammetric experiments to investigate the concentration and temperature dependency of the adsorption. The adsorption kinetics in buffer solution spiked with heavy metals follows a pseudo-second-order rate equation involving rate-controlling boundary layer adsorption and a side-by-side intraparticle diffusion process. Meanwhile, the adsorption tendencies under the studied conditions for TWP-f were Pb2+ > Cd2+. The equilibrium adsorption data were modulated by the Langmuir, Freundlich, and Dubinin-Radushkevich (DR) isotherms. Both the Freundlich and DR isotherms were found to be feasible for describing the adsorption on TWP-f. The adsorption energy obtained from the DR isotherm is 1.6 kJ mol−1 for Pb2+ and 2 kJ mol−1 for Cd2+, indicating physisorption as the dominating force. According to the Freundlich isotherm, multilayer adsorption is proposed. The thermodynamic parameters show that the adsorption of Pb2+ and Cd2+ is endergonic. Due to small Gibbs enthalpy values near the thermodynamic equilibrium, the adsorption process is mainly dependent on the ambient conditions. So, close-to-nature experiments were conducted to verify the received results. Therefore, tire and road wear particles including road sediments (TRWP+RS) were added to prefiltered freshwater samples of the river Freiberger Mulde (having naturally elevated trace element concentrations). The adsorption kinetics were investigated by ICP-MS/MS emphasizing the pseudo-second-order rate equation. Moreover, it is suggested that the tire wear particles in the TRWP+RS sample are majorly responsible for the adsorption of at least Cd2+.

Chitosan-based nano-sorbents: synthesis, surface modification, characterisation and application in Cd (II), Co (II), Cu (II) and Pb (II) ions removal from wastewater

In contemplation of treating hazardous industrial wastewater, sodium tripolyphosphate (TPP) and vanillin (V)-modified chitosan-based magnetic nano-sorbents (TPP-CMN and V-CMN) were prepared, and the physical and surface properties of both nano-sorbents were characterised. The results of FE-SEM and XRD showed an average size of between 6.50 and 17.61 nm for Fe3O4 magnetic nanoparticles. The Physical Property Measurement System (PPMS) was carried out, and the saturation magnetisations for chitosan, Fe3O4 nanoparticles, TPP-CMN, and V-CMN were 0.153, 67.844, 7.211, and 7.772 emu.g−1, respectively. By using multi-point analysis, the BET surface areas of the synthesised TPP-CMN and V-CMN nano-sorbents were found to be 8.75 and 6.96 m2/g, respectively. The synthesised TPP-CMN and V-CMN were investigated as effective nano-sorbents to uptake Cd (II), Co (II), Cu (II), and Pb (II) ions, and the results were investigated by AAS. The adsorption process of heavy metals was investigated by the batch equilibrium technique, and the sorption capacity values of Cd (II), Co (II), Cu (II), and Pb (II) ions by TPP-CMN were 91.75, 93.00, 87.25, and 99.96 mg/g. By V-CMN, the values were 92.5, 94.00, 88.75, and 99.89 mg/g, respectively. The equilibrium times for adsorption were found to be 15 minutes for TPP-CMN and 30 minutes for V-CMN nano-sorbents. The adsorption isotherms, kinetics, and thermodynamics were studied to understand the adsorption mechanism. Furthermore, the adsorption of two synthetic dyes and two real wastewater samples was studied and obtained significant results. These nano-sorbents’ simple synthesis, high sorption capability, excellent stability, and recyclability may provide highly efficient and cost-effective nano-sorbents for wastewater treatment.

Cellulose Nanocrystals (CNCs) and Cellulose Nanofibers (CNFs) as Adsorbents of Heavy Metal Ions

The isolation of nanocellulose has been extensively investigated due to the growing demand for sustainable green materials. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), which have the same chemical composition but have different morphology, particle size, crystallinity, and other properties depending on the precursor and the synthesis method used. In comparison, CNC particles have a short rod-like shape and have smaller particle dimensions when compared to CNF particles in the form of fibers. CNC synthesis was carried out chemically (hydrolysis method), and CNF synthesis was carried out mechanically (homogenization, ball milling, and grinding), and both can be modified because they have a large surface area and are rich in hydroxyl groups. Modifications were made to increase the adsorption ability of heavy metal ions. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG), and dynamic light scattering (DLS) can reveal the characteristics and morphology of CNCs and CNFs. The success and effectiveness of the heavy metal adsorption process are influenced by a few factors. These factors include adsorbent chemical structure changes, adsorbent surface area, the availability of active sites on the adsorbent’s surface, adsorption constants, heavy metal ionic size differences, pH, temperature, adsorbent dosage, and contact time during the adsorption process. In this review, we will discuss the characteristics of CNCs and CNFs synthesized from various precursors and methods, the modification methods, and the application of CNCs and CNFs as heavy metal ion adsorbents, which includes suitable isotherm and kinetics models and the effect of pH on the selectivity of various types of heavy metal ions.

Investigation of Efficient Adsorption of Toxic Heavy Metals (Chromium, Lead, Cadmium) from Aquatic Environment Using Orange Peel Cellulose as Adsorbent

Heavy metals in the environment cause adverse effects on living organisms. Agro-wastes have the potential to remove heavy metals from aqueous solutions. In this study, the orange peel cellulose (OPC) beads were utilized as adsorbents to remove metals from wastewater. The surface of the adsorbent was studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS). The concentrations of the metals before and after adsorption were measured using inductively coupled plasma mass spectrometry. The removal of the metal ions (i.e., Cr6+, Cd2+, and Pb2+) using the OPC was investigated by varying the pH, contact time, and adsorbent dosages parameters. The maximum removal efficiency obtained for the metal ions occurred at pHs 4–8. The use of the Langmuir isotherm and Freundlich isotherm models demonstrated the statistical significance of the heavy metal adsorption processes (R2 > 0.96). At a neutral pH, the OPC adsorption order was Pb2+ > Cd2+ > Cr6+ with % removal values of 98.33, 93.91, and 33.50, respectively. The adsorption equilibrium for Cr6+ was reached after 36 h. For Cd2+ and Pb2+, equilibrium was reached after 8 and 12 h, respectively. The FT-IR and SEM-EDS confirmed the presence of many functional groups and elements on the adsorbent. The adsorption of heavy metals using the OPC is a low-cost, eco-friendly, and innovative method for the removal of metals in aquatic environments. The findings of this study will be highly significant for the public in the affected areas worldwide that have credible health concerns due to water contamination with heavy metals.

Chemometrics approach for adsorption multi-response optimization of Cu(II), Zn(II), and Cd(II) ions from phosphoric acid solution using natural clay

This study describes the elimination percentage optimization of Cu(II), Zn(II), and Cd(II) heavy metal ions from a phosphoric acid solution (three-metal ions system) using a natural clay (NC). The response surface methodology (RSM) based on the central composite design (CCD) was used to maximize the elimination percentages of these heavy metals. The natural clay was characterized by FTIR, XRD, TGA-DTG, SEM, and EDX techniques. Several important parameters influencing the adsorption process of these ions in the multi-metallic mixture such as contact time (X1), temperature (X2), and mass of NC (X3) were investigated systematically by batch experiments. The fitted model indicated that the optimal conditions to simultaneously maximize the elimination percentage of these ions were 26.82 min, 16.26 °C, and 3.56 g of NC mass. Under these conditions, the numerical estimation of the elimination percentages was 71.10, 69.06, and 67.83% for Cu(II), Zn(II), and Cd(II), respectively. Freundlich and Langmuir’s models were fitted to evaluate the equilibrium data of the heavy metal adsorption process by natural clay. According to the obtained results, it appeared that Freundlich isotherm gives a good representation of the adsorption phenomenon of Cu(II) ions, and for the adsorption of Cd(II) and Zn(II) on NC, the data shows fit both Freundlich and Langmuir isotherm model.

Characteristics of adsorption behavior of potentially toxic metals by biochar derived from fallen leaves (Platanus) and its mechanism

In this study, we aimed to evaluate the properties and mechanisms of heavy metal adsorption by biochar derived from fallen leaves (FLB). The optimum manufacturing temperature of FLB for heavy metal removal was 650 °C, which resulted in a high carbon content and specific surface area. The maximum adsorption capacities of Cd and Pb by FLB650 were 86.2 and 135.1 mg/g, respectively; their adsorption was achieved via chemisorption. The results from chemisorption agreed with the Langmuir isotherm and pseudo-second order models. We confirmed that the adsorption of Pb by FBL was dominantly affected by the surface boundary layer; however, the adsorption of Cd occurred in cooperation with the boundary layer and pore diffusion; which was accomplished by employing the intraparticle diffusion model. After heavy metal adsorption, the distribution characteristics and mechanisms of each heavy metal in the FLB were noticeably observed through SEM-EDS, FTIR, and XRD. In addition, the content of exchangeable cations released from the FLB during the heavy metal adsorption process corresponded to 52% for Cd and 34% for Pb of the total amount of adsorbed heavy metals. We determined that FLB exhibits high affinity for heavy metals and its adsorption occurs via an adsorption mechanism based on the properties of FLB.

Adsorption of tetracycline and Cd(II) on polystyrene and polyethylene terephthalate microplastics with ultraviolet and hydrogen peroxide aging treatment

Microplastics (MPs) could serve as vectors of antibiotics and heavy metals through sorption and desorption. However, the combined adsorption process of antibiotics and heavy metals on aged MPs has rarely been studied. In this study, combined adsorption/desorption of tetracycline (TC) and Cd(II) on/from polystyrene (PS) and polyethylene terephthalate (PET) MPs, as well as ultraviolet (UV) and H2O2 aged MPs, was investigated. The specific surface areas of the MPs increased after UV and H2O2 aging. Adsorption experiments showed that the pseudo-second-order kinetic model and Freundlich model fitted adsorption of TC and Cd(II) on all of the MPs. The adsorption capacities of TC and Cd(II) were higher on aged MPs than on the pristine MPs, especially on H2O2 treated MPs. TC adsorption on the MPs was hardly affected by Cd(II), and Cd(II) adsorption was not significantly affected by TC when the solution pH value was below 8.0. Cd(II) slightly enhanced TC adsorption on the MPs at pH 8.0, especially on the aged MPs. The TC adsorption capacities increased with increasing pH, reaching a maximum at pH 5.0 or 6.0, and they then decreased, while the largest level of Cd(II) adsorption was at approximately pH 6.0. Adsorption of TC and Cd(II) on the pristine and aged MPs was thermodynamically favorable and spontaneous. The trend of the desorption rates of TC and Cd(II) from the MPs in different background solutions was ultrapure water < surface water < simulated gastric fluid. The desorption rates of TC and Cd(II) from the aged MPs were lower than those from the pristine MPs. The results revealed the mechanism of the TC and Cd(II) combined adsorption process on aged MPs, which will provide insight for understanding the aging process and its potential effects on sorption and desorption of antibiotics and heavy metals in the real environment.

Experimental and RSM study of hypercrosslinked polystyrene in elimination of lead, cadmium and nickel ions in single and multi-component systems

The aim of this research is to calculate mass transfer and diffusion coefficients of the phases interface, and hypercrosslinked polymer (HCP) pores in the heavy metal adsorption process. The experiments are carried out at a pH of 7, the temperature of 20 ℃, and the initial concentration of 100 mg/L for single and ternary systems and 80 mg/L in the binary systems. The diffusion coefficient, mass flux, and mass transfer coefficient for cadmium ions in the ternary system have measured 0.2963×10−20 m2/s, 0.0818×10−20 mol/m2.s, and 0.2662×10−15 m/s in 10 min, respectively, and the diffusion coefficient, mass flux, and mass transfer coefficient for cadmium ions in the ternary system have measured 0.1954×10−20 m2/s, 0.2153×10−20 mol/m2.s, and 0.4935×10−15 m/s in 50 min, respectively. In the isotherm discussion, kL of 0.03 L/mg, kF of 31.84 mg(1−m). Lm/g, and kS of 0.005(L/mg)m, and the KL of 5.92×10−8 and KL of 0.7588×10−15 m/s in boundary and pores for lead ions, respectively, which shows the direct relation between the isotherm constant and mass transfer coefficient. The mass transfer coefficient in the interface is higher than inside the pores, for instance, for lead ions, KL of 7.60×10−8 m/s and KL of 0.4463×10−15 m/s in boundary and pores, respectively. Besides, KL of 5.60×10−8 m/s and KL of 7.60×10−8 m/s in binary and ternary systems for lead ions, respectively, show a positive influence in increasing the components. Moreover, in the ternary system, KL for lead, nickel, and cadmium ions are 7.60×10−8, 5.51×10−8, and 6.30×10−8 m/s, respectively, which proves the high transfer of lead ions relative to the other ions. Ultimately, response surface methodology was employed and also observed that the quadratic relation between KL and dimensionless numbers was suitable.

有机肥连续施用对菜田重金属行为的影响——基于地球化学模型研究

PDF HTML阅读 XML下载 导出引用 引用提醒 有机肥连续施用对菜田重金属行为的影响——基于地球化学模型研究 DOI: 10.5846/stxb202101080087 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项A类（XDA26050202，XDA23050101）；国家重点研发计划（2017YFD0801404）；中国科学院青年创新促进会（2017073） Effect and simulation of continuous application of organic fertilizer on heavy metal behavior in vegetable field soil based on geochemical model Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:2017年起，农业部连续多年出台化肥减量增效行动工作方案，要求适当增加有机肥投入，发展循环农业。但连续施用的有机肥进入土壤后，会对土壤pH、有机质和重金属含量等产生影响，改变土壤重金属行为。科学评估有机肥料施用的影响至关重要。仅通过总含量评估重金属污染风险被认为是片面的，不同化学提取剂提取的重金属含量不能完全代表实际污染状况。地球化学模型具有良好的适用性，比传统的提取方法能够更全面地解释重金属的行为。在集约化农业种植区黄淮海平原，多次施用不同比例的粪源有机肥于旱地菜田，并引入地球化学模型，结合pH依赖性浸出试验，明确连续施肥对菜田土壤重金属行为的主要影响机制。研究发现，有机肥中的铜锌含量远高于土壤中的含量，施用后，它们在土壤中的淋溶浓度随着施用比例增加而显著增加，最多可超过十倍以上，并且活性大大增加，与施肥后溶解性有机物含量的升高呈正相关。不同处理条件下的土壤重金属浸出趋势相似：在中性pH下浸出浓度最低，然后逐渐向强酸和强碱增加，呈现出V型变化。地球化学模型LeachXS展示出较好的模拟结果，其模拟值与实测浓度具有良好的相关性（71.02%）。模拟结果显示，有机肥的施用不会明显改变重金属在土壤固相表面的主要吸附过程，但可以通过提高液相中溶解性有机物和重金属含量，增加重金属在土壤中的浸出，从而提升重金属的活性。有机物，铁铝（氢）氧化物，粘土矿物等决定了几乎所有重金属的浸出特性，其中土壤有机物（包括溶解性有机物和颗粒有机物）对重金属的吸附和络合作用大于其他物质，是影响重金属在土壤固液相间行为的最主要因素，随着有机肥添加比例提高，POM络合态重金属含量明显升高，并高于其他固相态，尤其是Cu、Zn、Cr，而DOM络合态重金属含量的升高直接导致了它们的活性增强。对于Ni、Pb，铁铝（氢）氧化物络合态与POM络合态含量接近或更高，但与施肥比例关系不明显。高DOM高铜锌含量的猪粪有机肥施用后会明显增加重金属在土壤和作物中的累积，连续施用和过量施用可能造成的土壤污染风险极高。在选择连续施用畜禽粪便有机肥时，必须减低其重金属含量并关注可能带来的污染，真正实现有机循环农业健康、可持续发展。 Abstract:Since 2017, the Ministry of Agriculture and Rural Affairs of China has introduced the action plan of chemical fertilizer reduction and efficiency improvement, which required an appropriate increase in organic fertilizer input and the development of circular agriculture. However, the continuous application of organic fertilizers into the soil will affect the soil pH, organic matter and heavy metal content, and change the soil heavy metal behavior. It is essential for scientific evaluation of the impact of organic fertilizer application. It is considered to be unilateral to evaluate the pollution risk only by the total content. The heavy metal content extracted by different chemical extractants cannot completely represent the actual pollution situation. The geochemical model has good applicability and can explain the behavior of heavy metals more comprehensively than the traditional extraction.In the Huang-Huai-Hai Plain, an intensive agricultural planting area, different proportions of manure-source organic fertilizer were continuously applied to dryland vegetable fields. A geochemical model was introduced, combined with a pH-dependent leaching test, to determine the main influence mechanism of continuous fertilization on soil heavy metal behavior. It found that the content of Cu and Zn in organic fertilizer was much higher than that in soil. After application, their leaching concentration in the soil increased significantly as the proportion of application increased, up to more than ten times, and the activity greatly increased, which was positively correlated with the increase in dissolved organic matter (DOM) content after fertilization. The soil under different treatments showed similar leaching trends. The leaching concentration of heavy metals appeared at a minimum at neutral pH, and gradually increased toward the strong acid and alkali (V-shaped). The geochemical model (LeachXS) showed good simulation results, and its estimated value had a good correlation (71.02%) with the measured concentration. The simulation results showed that the application of organic fertilizer would not significantly change the main adsorption process of heavy metals on the solid surface of the soil, but it could increase the leaching of heavy metals in the soil liquid phase by increasing the DOM and heavy metal content, thereby increasing the activity of heavy metals. Soil organic matter (SOM), Fe-Al (hdyr) oxides, clay, etc. determined almost all the leaching of heavy metals. Among them, SOM, including DOM and Particulate Organic Matter (POM), had greater adsorption and complexation of heavy metals than other substances, and was the most important factor affecting the behavior of heavy metals in soil between solid and liquid phases. With the increase in the proportion of organic fertilizer, the content of heavy metals (especially Cu, Zn, and Cr) of POM-bound increased significantly and was higher than other solid states. The increased content of the DOM-bound heavy metal directly led to their enhanced activity. For Ni and Pb, the content of Fe-Al (hdyr) oxides-bound was close to or higher than that of POM-bound, but the relationship with the fertilization ratio was not obvious. The application of pig manure with high DOM and high Cu and Zn content would significantly increase the accumulation of heavy metals in the soil and crops, and continuous application might cause extremely high pollution risks. When choosing continuous application of organic fertilizer from livestock and poultry manure, it is necessary to reduce its heavy metal content, and pay attention to possible pollution, to truly realize the healthy and sustainable development of organic recycling agriculture. 参考文献 相似文献 引证文献

Adsorpsi Logam Kadmium dalam Limbah Cair Buatan Menggunakan Biosorben Kulit Pisang Mas (Musa acuminate colla)

Mas banana ( Musa acuminata Colla) peel is a type of household waste as well as agricultural waste whose utilization still needs to be improved. In addition, among various types of heavy metals that are dangerous as contaminants in the environment, cadmium metal is a metal that is very dangerous to health even in very small amounts. Therefore, this study aims to not only utilize the waste of Mas banana peel ( Musa acuminata Colla) as a biosorbent, but also to determine the optimum conditions needed to reduce cadmium metal which involves several test parameters, namely stirring time, pH and mass of biosorbent. Variations of stirring time used include 10, 20, 30, 35, and 45 minutes; variations in pH used include 1, 2, 3, 4, and 5, while variations in the mass of biosorbent used include 0.5; 1; 1.5; 2 and 2.5 grams. The results showed that the optimum conditions were obtained at a mixing time of 35 minutes, pH 5, and a mass of 2 grams of biosorbent with a reduction percentage value of 78.45%. This percentage indicates that Mas banana peel can be used as a natural adsorbent for cadmium metal. In addition, the results of the FT-IR analysis of the Mas banana peel biosorbent showed that Mas banana peel has a functional group that plays a role in the heavy metal adsorption process.

Efficiency of eggshell as a low-cost adsorbent for removal of cadmium: kinetic and isotherm studies

Eggshell (ES) is an alternative source of calcium carbonate that efficiently removes heavy metals in aqueous solution. The adsorption capacity of ES depends on their physico-chemical properties and the influence of experimental conditions, but in the majority of reports, not all the reaction parameters related to adsorption process of heavy metals are available, and the adsorption mechanism is not systematically studied. In this contribution, the use of ES waste is reported to establish an overall performance trend of the experimental parameters on cadmium ion (Cd2+) adsorption from an aqueous solution. Different physicochemical techniques Brunauer–Emmett–Teller (BET), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) are used to characterize the physico-chemical properties of ES and the adsorption performance is studied as a function of contact time, pH, concentration, and adsorbent dosage. The highest adsorption capacity, 217.4 mg.g−1, obtained in 10 min at an initial pH = 5 with an adsorbent dose of 0.8 g.L−1, is mainly attributed to the high specific surface area of the eggshell used in this work. Adsorption kinetics are described by the pseudo-second-order model, in good agreement with the experimental data, and the sorption mechanism follows the isotherm model of Langmuir, characterized by the chemical adsorption of a homogeneous monolayer of Cd2+ on the surface of ES adsorbents. The desorption efficiency of cadmium ions is efficient in the presence of nitric acid. The outcomes provided by the study confirm the use of eggshell as an effective and inexpensive material, offering high efficiency for cadmium removal.

Enhanced simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi) ions from aqueous solution using cassava root husk-derived biochar loaded with ZnO nanoparticles.

This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi). By conducting batch-mode experiments, it was concluded that 3% w/w was the best impregnation ratio for the modification of CRHB using ZnO-NPs, and was denoted as CRHB-ZnO3 in this study. The optimal conditions for heavy metal adsorption were obtained at a pH of 6–7, contact time of 60 min, and initial metal concentration of 80 mg L−1. The heavy metal adsorption capacities onto CRHB-ZnO3 showed the following tendency: Pb(ii) > Cd(ii) > As(iii) > Cr(vi). The total optimal adsorption capacity achieved in the adsorption of the 4 abovementioned metals reached 115.11 and 154.21 mg g−1 for CRHB and CRHB-ZnO3, respectively. For each Pb(ii), Cd(ii), As(iii), and Cr(vi) metal, the maximum adsorption capacities of CRHB-ZnO3 were 44.27, 42.05, 39.52, and 28.37 mg g−1, respectively, and those of CRHB were 34.47, 32.33, 26.42 and 21.89 mg g−1, respectively. In terms of kinetics, both the pseudo-first-order and the pseudo-second-order fit well with metal adsorption onto biochars with a high correlation coefficient of R2, while the best isothermal description followed the Langmuir model. As a result, the adsorption process of heavy metals onto biochars was chemisorption on homogeneous monolayers, which was mainly controlled by cation exchange and surface precipitation mechanisms due to enriched oxygen-containing surface groups with ZnO-NP modification of biochar. The FTIR and EDS analysis data confirmed the important role of oxygen-containing surface groups, which significantly contributed to removal of heavy metals with extremely high adsorption capacities, comparable with other studies. In conclusion, due to very high adsorption capacities for metal cations, the cassava root husk-derived biochar modified with ZnO-NPs can be applied as the alternative, inexpensive, non-toxic and highly effective adsorbent in the removal of various toxic cations.

Facile synthesis of economical feasible fly ash–based zeolite–supported nano zerovalent iron and nickel bimetallic composite for the potential removal of heavy metals from industrial effluents

Heavy metals contamination of water is one of the environmental issue globally. Thus prepared fly ash–based zeolite (FZA)–supported nano zerovalent iron and nickel (nZVI/Ni@FZA) bimetallic composite from low-cost fly ash waste for the potential treatment of anion (Cr(VI) and cation Cu(II)) heavy metals from industrial effluents at pH 3 and 5, respectively in this study. The systematic interaction between FZA and nZVI/Ni and the adsorptive removal mechanism was studied. The mean surface area of the nZVI/Ni@FZA (154.11 m2/g) was much greater than that of the FZA (46.6 m2/g) and nZVI (4.76 m2/g) independently, as determined by BET-N2 measurements. The effect of influence factors on the removal of Cr(VI) and Cu(II) by nZVI/Ni@FZA, such as pH effect, initial concentration effect, time effect, temperature effect, coexisting metals, and ionic strength, and cumulative loading ability, were discussed. The maximum adsorption capacity of nZVI/Ni@FZA was 48.31 mg/g and 147.06 mg/g towards Cr(VI) and Cu(II), respectively. These were higher than those of nZVI@FZA and FZA. It demonstrated that Ni could play an important role in enhancing the reduction ability of nZVI. Furthermore, isothermal and kinetic results revealed that both heavy metal adsorption processes were rate limiting monolayer Langmuir adsorption on homogeneous surfaces. Thermodynamic results suggested that the adsorptive removal of metal ions was endothermic with spontaneity. The applicability of nZVI/Ni@FZA on real industrial wastewater treatment results demonstrate that the concentration of heavy metals were removed under the acceptable standard levels. Further the adsorption capacity of nZVI/Ni@FZA was higher than the nZVI@FZA and FZA. The overall results demonstrated that nZVI/Ni@FZA was a promising, efficient, and economically feasible sorbent for potential wastewater treatment. Moreover this is first report on the preparation nZVI/Ni@FZA bimetallic composite.

Synthesis of a novel magnetic nano-zeolite and its application as an efficient heavy metal adsorbent

A novel magnetic nano-zeolite (MNZ@MS) is successfully synthesized, characterized and applied to adsorp heavy metals from solution. In the synthesis of MNZ@MS, the fly ash magnetic sphere (MS) and [C18H37 (CH3)2-N+-(CH2)3 -N+-(CH3)2C18H37] Cl2 is used as carrier and directing agent, respectively. The characterization results of XRD, XRF, XPS and SEM demonstrate that the nano-scale (200–600 nm) Linde F(K) zeolite completely wraps the magnetic spherical fly ash particle, and the saturation magnetization value of MNZ@MS is around 17.7 emu g−1. MNZ@MS exhibits a favorable and efficient adsorption performances on heavy metals, and the maximum adsorption capacity of Cu, Cd and Pb on MNZ@MS is 59.9 mg g−1, 188 .6 mg g−1 and 909.1 mg g−1, respectively. The higher pH value in solution is more conducive to the adsorption process of heavy metals on MNZ@MS. The adsorption is a fast process, well represented by the pseudo-second-order model. Concerning the equilibrium behavior, Langmuir isotherm model are more suitable for describing the adsorption. Furthermore, in competitive adsorption system, the adsorption process of Pb is the most difficult to be interfered, and the order of adsorption advantage is Pb>Cu>Cd. MNZ@MS may be applied as a low-cost and efficient magnetic adsorbent for wastewater treatment to remove heavy metals.

Removal of Cr (VI), As (V), Cu (II), and Pb (II) using cellulose biochar supported iron nanoparticles: A kinetic and mechanistic study

Abstract Magnetic iron-carbon nanoadsorbents synthesized using cellulose biochar as the carbon support have demonstrated great potential for removal of heavy metals (Cr (VI), As (V), Cu (II), and Pb (II)). The effects of initial solution pH, adsorbent dosage, contact time, initial concentration and different iron mass loadings on metal ion adsorption were examined. In an attempt to avoid the capital and operating costs associated with mixing, all the adsorption experiments were conducted under no mixing conditions. Non-linear regression analysis was used to determine kinetic and isotherm parameters. The kinetics of Cr (VI), As (V), and Pb (II) uptake followed pseudo-second order while Cu (II) adsorption best fit pseudo-first order model. Weber intraparticle diffusion model applied to heavy metal uptake revealed multiple rate limiting steps representing different adsorption stages. The adsorption isotherms of all four heavy metals in this study were well fitted by three-, four- and five- parameter models indicating carbon encapsulated iron nanoparticles (CEINPs) possessed a heterogeneous surface. 40 wt% iron loaded CEINPs showed a maximum Langmuir adsorption capacity of 688.6 mg g−1 for the uptake of As (V), a significantly high value when compared to all previously tested iron-based adsorbents in literature. X-ray photoelectron spectroscopy measurements on the CEINPs before and after metal ion adsorption confirmed that heavy metal adsorption process involved interactions with the metallic iron core. Further, a detailed adsorption mechanism for each metal was postulated based on the observed results.

Polyvinylpyrrolidone-Aminopropyl-SBA-15 schiff Base hybrid for efficient removal of divalent heavy metal cations from wastewater

The mesoporous silica-polymer hybrid was prepared as an adsorbent for divalent heavy metals (Pb(II), Ni(II), and Cu (II)) from rice husk and polyvinylpyrrolidone (PVP) through three successive steps. The first is the preparation of the mesoporous silica (SBA-15), the second is grafting 3-aminopropyltrimethoxysilane on SBA-15, and the following step is the formation of Schiff base (PVP-SBA-15) between amine end-capped silica and PVP moieties. The materials were characterized by different techniques, including FTIR, low and wide-angle XRD, N2-adsorption, and HR-TEM. The NH2-SBA-15 displayed a moderate affinity toward heavy element ions under study. Grafting of PVP moieties introduces a high affinity toward heavy metal ions, and the adsorption is a well-fitted Langmuir adsorption model. A series of experiment adsorption equilibrium reported with SBA-15, NH2-SBA-15, and PVP-SBA-15, which showed an adsorption capacity of 128 mg/g (Cu (II)), 175 mg/g (Pb (II)) and 72 mg/g for Ni(II). Kinetic studies have shown that the best way to describe the adsorption process of heavy metals is pseudo-first-order. The value of ΔG°, ΔH°, and ΔS° demonstrated that the adsorption of heavy metals on the PVP–SBA-15 was endothermic in nature and spontaneous. These results exhibited that PVP–SBA-15 material has considerable competence in eliminating heavy metals from wastewater.

Synthesis, crystal structures and properties of five novel coordination polymers and application in removing heavy metals from water

To remove heavy metals from water, five novel coordination polymers (CPs) have been successfully synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction and further characterized by Fourier transform infrared spectrometer, elemental analyses, thermogravimetric analysis, and powder X-ray diffraction. In the adsorption experiment of heavy metal ions, we discovered that these CPs possess high adsorption efficiency (up to 99%) and high adsorption capacity (up to 348 mg/g) to remove the heavy metal ions in water. Adsorption kinetics and adsorption isotherms indicate that the mechanism of adsorption process of heavy metals by these materials conforms to the pseudo-second-order kinetic model and the Langmuir adsorption model, respectively. Besides, these novel adsorbents are sufficiently stable in water and can be reused. Consequently, these CPs are highly promising candidates for the removal of heavy metal ions from water.

Reduction of excessive heavy metals accumulation in drinking water with natural zeolites

This paper reports on the study of heavy metal removal from groundwater intended for human consumption using natural aluminosilicates of the zeolite group. The natural zeolite material has been extracted from the Sokirnica deposit located in the Zakarpattia Region in Ukraine. The central focus of this study was the course of the heavy metal adsorption process itself, in which natural zeolites were applied for the removal of Cr, Cd, Ni and Pb ions from aqueous solutions in the presence of large amounts of Ca and Mg ions, competing for ion exchange sites. The capacity of zeolite as an adsorbent was assessed with the use of adsorption isotherms prepared for the heavy metals under tests, whereas the mathematical description of the process was provided by Freundlich and Langmuir isotherm equations. The results from the analysis confirm the high efficiency, and thus the applicability, of zeolite deposits in water filtration. The effective Cr, Cd, Ni and Pb removal rate from groundwater intended for human consumption was confirmed even when the content of these metals in water was exceeded by a factor of 10, compared to the permissible limits provided in legal regulations.