Initial Heavy Metal Research Articles

Sugarcane Bagasse Based Adsorbents and their Adsorption Efficacy on Removal of Heavy Metals from Nakuru Industrial Wastewater: Optimization, Kinetic and Thermodynamic Aspects

Currently, researchers are seeking to reduce heavy metal contamination from the environment, using agricultural waste materials like rice husk, groundnuts shells among others. The study focused on the removal of Cu(II), Pb(II), Cd(II), Ni(II), and Cr(III) ions from aqueous solutions and Nakuru industrial wastewater using sugarcane bagasse (NSCB) and valorised bagasse ash (VSCB), as alternative low-cost agricultural waste bio-sorbents. To achieve this goal, sugarcane bagasse was collected from Nzoia sugar industry in western Kenya, while the valorised bagasse was obtained by heating sugarcane bagasse sample in a muffle furnace at 300°C for three hours. Furthermore, batch adsorption studies were performed, and the effects of several factors, i.e. adsorbent particle size, pH, contact time, initial heavy metal ions concentration and temperature were investigated to optimise the removal efficiency of Pb, Cu, Cd, Ni, and Cr. The optimal adsorption conditions were pH of 5.0, adsorbent dosage of 0.1 g and ≤ 150µm particle size, equilibrium time of 60 minutes and at 25 degrees Celcius. The removal kinetics of the metal ions onto both adsorbents fitted well with the pseudo-second-order model. The removal kinetics of the metal ions onto both adsorbents fitted well with the pseudo-second-order model. The adsorption of Pb2+ and Ni2+ onto NSCB fitted better with the Freundlich isotherm model, while Cd2+, Cu2+ and Cr3+ showed better fit for the Langmuir isotherm model. As for VSCB adsorbent, Cr3+ has a better fit with the Langmuir isotherm model whereas Pb2+, Ni2+, Cd2+, and Cu2+ fitted well on the Freundlich isotherm model. Freundlich constant’s (1/n) values and the separation factor (RL) from the Langmuir isotherm model indicate that the metal ions were favourably adsorbed onto the adsorbents. Langmuir isotherm model was used to estimate the maximum adsorption capacities (qmax) for Cu(II), Pb(II), Ni(II), Cd(II), and Cr(III). The negative free energy change (∆G) values revealed that adsorption process of the metal ions onto NSCB and VSCB was spontaneous. Fourier Transform Infrared Spectroscopy (FTIR) was used for characterization studies. Interactions with metal ions caused the frequencies of the active functional groups, –OH, C=O and C=C, on the bio-sorbent surfaces to shift to higher values. Therefore, sugarcane bagasse and valorised bagasse have demonstrated higher potential to remove relatively all selected heavy metals in the industrial wastewater at controlled pH.

The superior adsorption capacity of biogenic α-Mn2O3 in comparison to chemogenic α-Mn2O3 for five divalent heavy metal cations and the adsorption mechanism of biogenic α-Mn2O3: Experimental and DFT investigations

Manganese oxides play a crucial role in the adsorption of heavy metals in the environment. However, there is currently a lack of information regarding the comparative adsorption efficiency of heavy metals between biogenic and chemogenic manganese oxides. In this work, we compared the adsorption performance of biogenic and chemogenic α-Mn2O3 towards Pb(II), Cd(II), Cu(II), Zn(II) and Ni(II). Mineral characterization analyses revealed that biogenic α-Mn2O3 exhibited a polycrystalline nature, whereas chemogenic α-Mn2O3 displayed a monocrystalline nature with a lower impurity content compared to biogenic α-Mn2O3. Under acidic conditions, biogenic α-Mn2O3 demonstrated a significantly higher adsorption capacity, ranging from 3 to 6 times greater than its chemogenic counterpart, within an initial heavy metal concentration range of 0.2–1.0 mM. This superiority can be attributed to the presence of more abundant functional groups and a greater content of hydroxyl O species on the surface of biogenic α-Mn2O3 in comparison to chemogenic α-Mn2O3. During the adsorption process of biogenic α-Mn2O3, there were observed ionic exchanges between Mn(II) and these cations. More importantly, biogenic α-Mn2O3 bound with these cations probably through the formation of -O/OH/S complexes. The adsorption selectivity of biogenic α-Mn2O3 towards the five heavy metals was experimentally determined to follow the order of Ni(II) > Pb(II) > Cu(II) > Zn(II) > Cd(II). The electronic interaction between biogenic α-Mn2O3 and these cations indicated that Ni(II), Pb(II) and Cu(II) were more likely to share electrons with O atoms on the surface of biogenic α-Mn2O3 compared to Zn(II) and Cd(II).

Adsorption of heavy metal ions by carbon-based adsorbent using magnetic nitrogen-doped carbon and graphene oxide

ABSTRACT The adsorption of weighty metal particles from contaminated water sources has garnered significant attention due to its critical role in environmental remediation and ensuring safe drinking water. Heavy metal ions can be removed from water using conventional adsorbents such as activated zeolites; however, these materials have low absorption and slow kinetics. To solve these issues, carbon-based adsorbents that exhibit easy synthesis, high porosity, design ability, and stability have been proposed. In this review, a carbon-based adsorbent, named M-NC, and graphene oxide were created for the particular evacuation of weighty metal particles. To increase the potential for Heavy Metals (HM) immobilization, sulfide-modified biochar was created via a process called synchronous carbon layer epitome. A hypothetical physicochemical and thermodynamic examination of the adsorption of weighty metals Zn2+, Cd2+, Ni2+, Ag2+, Pb2+ and Cu2+ on carbon-based adsorbents was done with factual material science fundaments. The biochar with large surface areas is utilized to eliminate weighty metal particles, quite possibly the most significant heavy metal pollutants, from aqueous solutions. The limit of the adsorbent for eliminating weighty metal ions was concentrated on utilizing Langmuir adsorption isotherm under ultrasound-helped conditions. The Mesoporous Silica Nanoparticles (MNCs) can be applied to the Langmuir model and pseudo-second-order kinetics. It is possible to use the Langmuir and second-order kinetic equations to accurately explain the adsorption method. Thermodynamic limitations were also envisioned because sorption is exothermic when it happens spontaneously. A homogeneous measurable physical science adsorption typically was utilized to describe and analyze the experimental heavy metal removal isotherms at 30°C and pH5 utilizing adsorbents produced by pyrolysis of biomasses (broccoli stalks). The experimental results were investigated in terms of Langmuir and pseudo-2nd-order kinetic equations, Freundlich and isotherm models. The outcome of pH, initial heavy metal ion concentration, contact time, and adsorbent dosage regarding the adsorption capacity and removal efficiency of Pb2+ and Cd2+ on the hydrogel was examined. This study contributes to the advancement of information in the ground of environmentally friendly heavy metal removal techniques, specifically focusing on the usage of biomass-based adsorbents. These findings have the potential to address the need for effective solutions in water purification and environmental cleanup efforts.

Applications of Ion Exchange in Environmental Remediation: Removal of Heavy Metals From Wastewater

ABSTRACTThe concern over heavy metal contamination and its impact on human health and the environment has led to a growing interest in cost‐effective and sustainable remediation technologies. Ion exchange is recognized as an efficient method for removing heavy metal ions from wastewater. This study focused on the removal of heavy metal ions (Ni, Cu, Zn, and Pb) from aqueous solutions using the extended batch equilibrium technique. Experimental trials were conducted using Purolite C100, a strong acid ion‐exchange resin, to assess the influence of various treatment parameters such as pH, contact time, sorbent dosages, and initial heavy metal concentrations on the removal efficiency. The results indicated that significant treatment equilibrium could be achieved within 1 h. Notably, pH levels between 5 and 6 had a significant impact on heavy metal removal, with adsorption capacities of 71, 67, 66, and 62 mg/g for Ni, Cu, Zn, and Pb, respectively. Furthermore, the equilibrium data obtained from the batch experiments were well fitted with Langmuir, Freundlich, and pseudo‐first‐order kinetic models. Statistical analysis revealed a strong correlation with the Langmuir isotherm model, highlighting its superiority over the Freundlich isotherm and pseudo‐first‐order kinetic models.

Batch adsorption studies on copper removal from an aqueous solution using natural zeolite: Process optimization

Abstract The ability of natural zeolite to remove copper ions from an aqueous solution was examined. The research aims to optimize adsorption operational variables, which include the amount of zeolite, pH, contact time, and initial heavy metal concentration for copper removal using zeolite. The research was conducted in batch experiments. The ranges of operational conditions are as follows: 0.2 - 1.0 g of zeolite, pH 4 - 8, 2 - 60 minutes of contact time, and 5 - 50 mg/L of initial concentration of copper. The outcomes indicated that the percentage removal of copper using zeolite achieved the best performance at an optimized adsorbent dosage of 1.0 g, a pH of 6, a contact time of 20 minutes with 135 rpm, and an initial copper concentration of 5 mg/L. To sum up, zeolite is an efficient adsorbent that is capable of separating copper from water-based solutions.

Investigating the possibility of using a mixture of thorium with different fissile materials as a fuel in TRISO particles for the PBMR-400 reactor

The increasing demand for nuclear reactors as a source of clean energy forced nuclear researchers to search for ways to enhance the safety operation of nuclear reactors. This paper discusses the viability of using different thorium compounds ((233U, Th)O2, (235U, Th)O2, (RGPu, Th)O2) as an accident tolerant fuel/advanced technology fuel (ATF) for Pebble Bed Modular Reactor 400 (PBMR-400). A comprehensive analysis of thorium-based fuel performance was carried out and compared with UO2 to develop a novel nuclear fuel with the capability to tolerate severe accident conditions. The neutronic characteristics such as the infinity multiplication factor, initial heavy metal concentration, RGPu concentration and fission products concentration were analyzed. In addition to, the main safety parameters have been calculated to distinguish the effect of the proposed fuels on them. The thermal spectrum and thermal output power have been visualized to give a good insight view inside the core about the distribution of the heat. In general, the neutronic analysis demonstrated good behavior of the examined thorium-based fuel in the PBMR-400 and especially in the case of (RGPu, Th)O2. PBMR-400 showed excellent performance in incinerating a large amount of reactor-grade plutonium when it was used in a kernel fuel bed.

Efficient separation of Cd2+ and Pb2+ by Tetradesmus obliquus: Insights from cultivation conditions with competitive adsorption modeling

Microalgae serve as efficient biosorbents for the removal of heavy metals. This study investigates the adsorption and desorption behavior of Tetradesmus obliquus FACHB-14 (T. obliquus) under various culture conditions. Glucose cultivation enhances adsorption, with Pb2+ exhibiting higher capacity than Cd2+, reaching a maximum of 80.24 mg/g at an initial heavy metal ion concentration of 64 mg/L. Kinetic modeling favors the pseudo-second-order kinetics. The Langmuir model is more suitable for describing the adsorption process of Cd2+ in BG11 and Pb2+ in glucose, with maximum adsorption capacities of 6.48 mg/g and 86.29 mg/g, respectively. The Temkin model is more suitable for describing the adsorption process of Pb2+ in BG11 and Cd2+ in glucose. Competitive adsorption reduces the maximum capacity by 42.60 % for Cd2+ and 55.61 % for Pb2+. The Extended Freundlich model fits competitive behavior. Analysis reveals increased extracellular polymer secretion under glucose conditions, which aids adsorption. Na2EDTA achieves up to 97.37 % recovery of heavy metal ions. Overall, T. obliquus cultured with glucose shows promise for heavy metal removal, especially in mixed systems.

Characterization of Red Mud-based Curing Agent for Curing High Concentration Copper Contaminated Soil

In order to investigate the characteristics of RCP (red mud: calcium carbide slag: cement = 3:1:1) curing agent for curing soil with high concentration of copper contamination, this paper carried out the unconfined compressive strength test, toxicity leaching test, electrical resistivity test, and scanning electron microscopy test on RCP specimens with different age of maintenance, different curing agent dosages and different initial heavy metal contamination concentrations to investigate and analyze the Unconfined compressive strength characteristics, heavy metal ion leaching concentration characteristics and resistivity characteristics of RCP cured soil under different variables.It was found that the unconfined compressive strength and resistivity of RCP cured soil increased with the increase of maintenance age and curing agent dosing, while the strength and resistivity of cured soil decreased when the initial heavy metal contamination concentration increased. The heavy metal ion leaching concentration of RCP cured soil decreased with the increase of maintenance age and curing agent dosage, while the heavy metal ion solidification rate of cured soil decreased when the initial heavy metal pollution concentration increased.By observing and analyzing the swept electron microscope images of RCP specimens maintained for 28 days, the presence of Calcovanite, hydrated calcium silicate and hydrated calcium silica-aluminate can be observed, and these hydration reaction products enhance the strength of the cured soil, as well as displace and adsorb heavy metal ions in the contaminated soil, which have a better curing effect on the heavy metal ions.

Alternating Direct Current Field Assistant Promoting Chemical Stabilization of Combined Heavy Metals Contaminated Soil

To enhance the remediation efficiency and reduce the chemicals consumption, the combined heavy metals Lead (Pb), Copper (Cu) and Cadmium (Cd) contaminated soil were stabilized by chemical passivators with alternating direct current field (ADC) assistant. The results showed that ADC treatment activated initial heavy metal compounds in the soil. The leaching concentrations of Pb, Cu and Cd in soil under ADC condition increased by 19.61%, 38.77% and 49.10% in comparison with no electric field, respectively. The exchangeable fractions of Pb, Cu and Cd increased while the reducible, oxidizable and residual fractions decreased substantially. Thus, the chemical passivators addition companied with ADC treatment in the beginning increased stabilization efficiency of heavy metals in the soil and reduced over 30% amount of chemical agent consumption, comparing with only chemical passivator stabilization. The mechanism can be speculated that ADC assistant facilitated more heavy metal ions in the soil reacting with phosphorus- containing passivator to formed more complex and stable metal phosphates. It was confirmed by XRD measurement that silicon element in the crystal structure of metallic compound was replaced by phosphorus element.

Effects of ultrasounds and microwaves on the morphology and adsorption capacity of calcium alginate

Three non-conventional strategies have been used to prepare calcium alginate (CaAlg) from sodium alginate (NaAlg) by a batch process: ultrasound (US); microwave (MW) and combined US-MW. The calcium alginates obtained were used to remove Pb(II) and Cd(II) from single and binary aqueous solutions. The resulting adsorption capacities were compared to those obtained by conventional synthesis of calcium alginate. Scanning electron microscopy (SEM) revealed that the use of microwave and ultrasound produced CaAlg beads with roughened surfaces and consequently with increased specific surface area. The optimum parameters for the removal of Pb(II) and Cd(II) ions from single and binary solutions were determined in terms of pH, contact time, adsorbent dose and initial heavy metal concentration. A significant increase of the maximum adsorption capacity of Cd(II) and Pb(II) ions determined from Langmuir isotherm model was recorded in the case of CaAlg particles prepared in the combined microwave and ultrasound system. These values are 1.7389 ± 0.0585 mmol/g for Cd(II) and 1.5872 ± 0.0657 mmol/g for Pb(II) compared to 0.9305 ± 0.0926 mmol/g and 0.9735 ± 0.0572 mmol/g, respectively recorded for CaAlg particles prepared and matured using the conventional method. The differences between the values of the adsorption capacity of CaAlg-C-C for Pb(II) compared to Cd(II) ions is due to the Pb(II) ions characteristics (ion radius, hydrated ion radius, electronegativity). Thus, it can be stated that use of a combination of microwave and ultrasound improved the adsorption capacity of CaAlg for the removal of heavy metal ions from polluted effluents.

Heavy Metal Remediation from Water/Wastewater Using Bioadsorbents - A Review

This paper aims to emphasize heavy metals’ impact on water and its removal mechanism with a focus on adsorption. Furthermore, factors affecting bio adsorption, such as temperature, pH, RPM, and initial heavy metal concentration, have been studied for different heavy metals and bioadsorbents. A comparison of their adsorption capacities and efficiencies has been made. This review reviewed different bioadsorbents for their suitability in removing cadmium, lead, and copper ions from water and wastewater, typically by using adsorption as a methodology. A suitable summary compares various heavy metal removal techniques and their advantages and limitations. For adsorption, the characteristics of bioadsorbents and their activation steps have been consolidated. Furthermore, the effects of operational parameters and adsorption mechanisms have been discussed in the review. Apart from assessing the suitability of bioadsorbent, a novel bioadsorbent has been suggested for copper ions removal. The findings shall be significantly useful in applying bioadsorbent in water/wastewater treatment fields to reduce heavy metal pollution. Thorough and well-planned research in this field can facilitate the creation of sustainable and durable technology for wastewater treatment, addressing the increasing demand for safe and dependable water resources, focusing on making it cost-effective and recyclable.

Sulfate-reducing bacteria-based bioelectrochemical system for heavy metal wastewater treatment: Mechanisms, operating factors, and future challenges

Heavy metal wastewater (HMW) has resulted in many adverse environmental issues. However, bioelectrochemical system (BES) has been recognized as an effective technology for HMW treatment. This technology generates electricity and removes heavy metals and high concentrations of sulfate. In the sulfate-reducing bacteria-based BES, sulfate-reducing bacteria can anaerobically reduce sulfate to produce sulfide, which reacts with heavy metal ions and forms their corresponding sulfide precipitates, or the heavy metals can be reduced by obtaining electrons at the anode or cathode of the BES. Therefore, this study comprehensively reviews the removal mechanisms of HMW at the anodes and cathodes of the BES. The effects of several key factors, such as electrode materials, biocathode, initial heavy metal concentration, external resistance, and pH, on electricity generation performance and removal efficiency were evaluated. Furthermore, the treatment effects of the microbial fuel cell-microbial electrolytic cell system and the coupled system of BES with plants, artificial wetlands, and electrolytic reactors on HMW and the recovery efficiencies of BES for sulfur and heavy (precious) metals were discussed. Therefore, this review provides a theoretical basis and technical support to broaden the prospects of BES application in HMW remediation.

High surface area peat moss biochar and its potential for Chromium metal adsorption from aqueous solutions

Activated carbons (ACs) have been synthesized using local peat moss biomass for adsorption of heavy metal ions. Adsorbents with different surface areas and pore sizes were obtained using a chemical activation route with different impregnation ratios (20%, 30%, and 40%) of phosphoric acid. The carbonization process was carried out in a tubular furnace under flow of nitrogen (N2) at 500 °C, and 600 °C. Physicochemical properties of developed activated carbon have been evaluated by several techniques such as; X-ray diffraction, Scanning Electron Microscopic, Energy Dispersive X-ray Spectroscopy, Nitrogen adsorption isotherm, Pore size distribution analysis, and Fourier-transform analysis. Moreover, adsorption of chromium ions (Cr+2) from an aqueous solution under different variables was carried out. Heavy metal concentration (20 - 200) ppm, the dosage of adsorbent (0.1 – 0.5) g/L, the time of contact (0 - 220) min, and initial pH (2 - 8) were studied. Results showed that a synthesis route by chemical activation with 30% H3PO4 concentration at 600 °C for 3 h gave the highest BET surface area and pore volume (1692.6 m2/g and 1.55 cm3/g) respectively, compared with other prepared samples. As well as, the removal results show that the maximum adsorption capacity was 493.3 mg/g at 200 mg/L of initial heavy metal concentration, 6.5 pH, 0.3 g/L activated carbon dosage, and 180 min contact time. The Freundlich isotherm was the better description of the adsorption equilibrium data, while the pseudo-second-order model shows the most accurately describes of adsorption kinetics, which indicates that chemisorption is dominant in the adsorption process. Temperature and thermodynamics parameters were studied. The positive value of enthalpy indicates that the adsorption was endothermic.

The advanced characterization, post-irradiation examination, and materials informatics for the development of ultra high-burnup annular U-10Zr metallic fuel

U-Zr metallic fuel is a promising fuel candidate for Gen Ⅳ fast spectrum reactors. Previous experimental irradiation campaigns showed that the sodium thermal bonded U-10Zr fuel design can achieve a burnup of 10% fissions per initial heavy metal atom (FIMA). Advanced metallic fuel designs are pushing the burnup limit to 20% or even 30% FIMA. To achieve the higher burnup and eliminate the pyrophoric sodium, a prototypical annular fuel has been designed, fabricated, clad with HT-9 in the Materials and Fuels Complex, and irradiated in the Advanced Test Reactors of Idaho National Laboratory (INL) to a peak burnup of 3.3% FIMA. During irradiation, the mechanical contact between fuel and cladding acts as a thermal bond. The irradiation lasted for 132 days in the reactor. Recently, the archived fresh and irradiated fuel samples were characterized using advanced characterization capabilities in the Irradiated Materials Characterization Laboratory (IMCL) of INL. This article summarizes the results of advanced characterization and computer vision-based materials informatics to reveal the irradiation effects on U-Zr metallic fuel. Future work will focus on further implementation of advanced characterization and statistical data mining to improve the fidelity of fuel performance modeling and support U-Zr metallic fuel qualification for fast spectrum reactors.

Lipid-extraction algal biomass for biosorption of bivalent lead and cadmium ions: Kinetics and isotherm

Residual algal biomass, which is the by-product of the extraction of value-added products such as lipids, proteins, pigments and antioxidants, represent a potentially massive and inexpensive source of biosorbents. The biosorption of heavy metal Pb(II) and Cd(II) by the residual biomass of Chlorella vulgaris after lipid extraction was investigated under varied conditions including pH, contact time and initial heavy metal concentration. That of the wet and dried biomasses of C. vulgaris were also studied for comparison. Biosorption plateaus were achieved within 10 min for Pb(II) and 30 min for Cd(II). The Pb(II) biosorption capacities of by residual, wet, and dried biomass were 262.29, 114.85 and 82.81 mg/g, respectively, and that of Cd(II) were 55.13, 33.21, and 21.41 mg/g, respectively. The biosorption capacities of the residual biomass for Pb(II) and Cd(II) were 3.18 and 2.58-fold of that of dried biomass, which can be attributed primarily to the increased specific surface area.

Optimized removal of cadmium, copper and lead from wastewater by biosorption using cabbage waste and Box-Behnken design (BBD)

In this study a Box-Behnken (BBD) design was applied to optimize biosorption of copper, cadmium, and lead using cabbage waste. The effects of operating parameters including initial pH, biosorbent dosage, contact time, and heavy metal concentration were determined by BBD. The maximum biosorption removal efficiency was achieved at pH 4, 300 min operation time, 1.5 g/250 mL biosorbent dosage, and an initial heavy metal concentration of 25 mg/L. The maximum removal efficiencies were 77.23% for Cu, 93.10% for Pb, and 67.19% for Cd at optimal conditions. The cabbage waste was found to be an effective, sustainable, locally available, and environmentally friendly biosorbent for removing heavy metals from aqueous solution.

Evaluating Quantities of Interest Other Than Nuclide Densities in the Bateman Equations

Traditionally, analysts solve the Bateman depletion equations to calculate the nuclide number density (NND) of each nuclide since these densities impact other reactor parameters, such as reactivity, as they change. Many quantities of interest, such as radiation damage, are calculated using simple integration methods, assuming that the NNDs are constant over a given depletion interval. However, the NNDs are time dependent, which can be accurately represented only by the Bateman depletion equations. We propose that these quantities can be calculated simultaneously with the NNDs within the Bateman depletion equations, preserving the coupled nature of these quantities to the time-dependent NNDs. We implemented this functionality in Griffin, demonstrating that only minor code modifications were necessary in order to accommodate an evaluation of these quantities in the Bateman depletion equations. The Chebyshev Rational Approximation Method was used to successfully solve for these additional quantities in the Bateman depletion equations. For radiation damage, the results calculated by Griffin were very accurate, differing by less than 2.5% from an analytical benchmark. For other quantities, the discrepancy between quantities calculated by the Bateman depletion equations versus those calculated by the Forward Euler method exceeded 10% for decay energy and 2% for fissions per initial heavy metal atom and kinetic energy released per unit mass when few depletion intervals were used. As the number of depletion intervals increased, both methods began to converge as expected.

Cu(II) and Cr(VI) Removal in Tandem with Electricity Generation via Dual-Chamber Microbial Fuel Cells

Microbial fuel cells (MFCs) have shown great advantages in electricity production, heavy metal removal, and energy recovery. However, the impact and mechanism of conflicting effects of numerous electron acceptors on heavy metal removal remain unknown. The effects of different initial heavy metal concentrations, cathodic dissolved oxygen, and electrode materials on the electricity generation and heavy metal removal efficiencies of Cu(II) and Cr(VI) were investigated in this study. When the initial concentration of Cr(VI) increased from 10 mg/L to 150 mg/L, the maximum voltage, coulomb efficiency, and maximum power density declined from 99 to 44 mV, 28.63% to 18.97%, and 14.29 to 0.62 mW/m2, and the removal efficiencies of Cu(II) and Cr(VI) decreased dramatically from 98.34% and 99.92% to 67.09% and 37.06%, respectively. Under anaerobic cathodic conditions, the removal efficiency and removal rate of Cu(II) and Cr(VI) were lower than those under aerobic conditions. When the cathode electrode was titanium sheet and graphite plate, the coulomb efficiency and maximum power density increased to 38.18%, 50.71%, 33.95 mW/m2, and 62.23 mW/m2. The removal efficiency and removal rates of Cu(II) and Cr(VI) were significantly increased to 98.09%, 86.13%, and 0.47, 0.50 mg/(L h) with a graphite plate, respectively. The pH of the cathode varied considerably greater as the MFC current increased. Cu(II) and Cr(VI) were removed and reduced to elemental Cu, Cu2O, and its oxides as well as Cr(OH)3 and Cr2O3 precipitates on the cathode electrode by cathodic bioelectrochemical reduction.

Fir sawdust as a low-cost and easily recyclable adsorbent: efficient removal of Pb(II), Cu(II), and Zn(II) contaminants from wastewater.

The main pollution sources of heavy metals are the arbitrary discharge of industrial wastewater and waste residues, which cause serious harm to the water environment, soil environment, and human health. In this study, following the principle of waste utilization, a gel adsorbent (AA-SW-AMPS) was prepared by microwave-assisted chemical cross-linking using fir sawdust as raw material. A scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and swelling dynamic experiments were used to investigate the microstructure, reaction mechanism, and water absorption performance of AA-SW-AMPS. The N2 adsorption-desorption curve shows that the porous structure of AA-SW-AMPS creates 240.75 cm2/g of specific surface area to enable excellent heavy-metal sorption. It was determined by adsorption experiments that the optimal adsorption state was when the dosage of AA-SW-AMPS was 5g/L, the pH of the solution was 5, the adsorption time was 45min, and the initial heavy metal ion concentration was 250mg/L. In addition, the adsorption mechanism was investigated using adsorption dynamics, adsorption isotherm, and Materials Studio simulation. The results show that the maximum adsorption capacities of AA-SW-AMPS for Pb(II), Cu(II), and Zn(II) were 253.49mg/g, 237.29mg/g, and 232.15mg/g, respectively, and the adsorption mechanism is monolayer chemisorption. The adsorbent showed great potential in removing heavy metals from wastewater.

Experimental study on adsorption properties of functional magnetic nanomaterials for heavy metal pollutants

In order to effectively remove heavy metal pollutants and improve the quality of the ecological environment, the experimental study on adsorption properties of functional magnetic nanomaterials for heavy metal pollutants was studied. Magnetic nano-Fe3O4 materials were prepared by hydrothermal method. Fe3O4, Fe3O4@SiO2 and 3NH2-Fe3O4@SiO2 magnetic nanomaterials were obtained by functional modification. The adsorption properties of functionalised magnetic nanomaterials for Cd(II) and Pb(II) in water were analysed by batch test. The results show that 3NH2-Fe3O4@SiO2 has the highest adsorption capacity for Cd(II) and Pb(II); with decreasing temperature, the order of adsorption capacity for Pb(II) is Fe3O4 > Fe3O4@SiO2 > 3NH2-Fe3O4@SiO2. The Langmuir adsorption isotherm model can better fit the adsorption process of functionalised magnetic nanomaterials to Cd(II) and Pb(II) solutions. In different initial heavy metal solution concentration systems, the materials can promote the adsorption of Cd(II) and Pb(II) adsorption.