Enhanced removal of microplastics from wastewater treatment plants by a novel magnetic filter.

Microplastics (MPs) discharged from wastewater treatment plants (WWTPs) have emerged as serious pollutants in aquatic environments. Herein, a new magnetic filter (MFA) was prepared using an acidification-magnetization method with fly ash (FA) as the base material. The filter specifically targeted the removal of 1-µm polystyrene microspheres (PSMPs) because of the challenges they pose in filtration processes. The findings demonstrated that MFA filter exhibited superior PSMPs removal efficiency, with increases of 219%, 250%, and 288% compared to FA at flow rates of 1, 3, and 5 mL min-1, respectively. Scanning electron microscopy and other characterizations provided insights into the removal mechanisms of PSMPs using the MFA filter, which combined electrostatic attraction, π-electron conjugation, hydrogen bonding, and complexation. Environmental variables, such as solution pH, ionic strength, and dissolved organic matter, were identified as considerable influences in the removal process of PSMPs. The practical application confirmed that the MFA filter considerably promoted the elimination of MPs from the secondary treatment effluent of WWTPs without having any toxic effects on freshwater fish. Thus, this study provides a new approach to the resource utilization of FA, which would prominently promote its application prospects in MPs immobilization and removal from wastewater effluent.

Material flow analysis of heavy metals in large-scale cattle farms and ecological risk assessment of cattle manure application to fields.

This study bridges the knowledge gap pertaining to the pathways of heavy metal accumulation and migration within the industrial chain of large-scale cattle farms. Two such farms in Shaanxi serve as a basis for our exploration into Zn, Cu, Cr, Pb, As, and Cd dynamics. Employing material flow analysis complemented by predictive models, we evaluate the potential ecological risks of arable soil from heavy metal influx via manure application. Our findings indicate that Zn and Cu predominate the heavy metal export from these operations, composing up to 60.00%-95.67% of their total content. Predictive models based on 2021 data reveal a potential increase in Cd soil concentration by 0.08 mg/kg by 2035, insinuating a reduced safe usage period for cattle manure at less than 50 years. Conversely, projections from 2022 data point towards a gradual Cu rise in soil, reaching risk threshold levels after 126 years. These outcomes inform limitations in cattle manure utilisation strategies, underscoring Cu and Cd content as key barriers. The study underscores the criticality of continuous heavy metal surveillance within farm by products to ensure environmental protection and sustainable agricultural practices.

Immobilization of cadmium in paddy soil using a novel active silicon-potassium amendment: a field experimental study.

The rapid development of industrialization and agriculture has led to extensive environmental issues worldwide such as cadmium (Cd) pollution of paddy soils, posing a potential threat to environmental safety and food health. Therefore, there is an urgent need to reduce the Cd contents in paddy soils. In this study, a newly active silicon-potassium amendment was first prepared from potassium hydroxide-assisted potassium feldspar at a low temperature, and then was used to remediate a contaminated paddy soil by Cd over a long period. The obtained results demonstrated the effectiveness of the applied active silicon-potassium in promoting rice growth in the experimental field. In addition, soil pH values increased to 6.89-7.03, thus decreasing the bioavailability of Cd bioavailability by 8.61-13.7%. The soil enzyme activities and available nutrients (Si, Ca, Mg, N, and P) were also significantly increased. In particular, the Cd contents in the rice grains decreased from 0.279 to 0.179-0.194 mg/kg following the application of the active silicon-potassium amendment, reaching the food crop standard level of China (< 0.2 mg/kg). The detailed remediation mechanisms of the Cd-contaminated paddy soil involved several processes, including ion exchange, ligand complexation, electrostatic attraction, and precipitation. Overall, the active silicon-potassium material is a promising amendment for achieving effective control of Cd-contaminated paddy soils.

Utilization of KOH-modified fly ash for elimination from aqueous solutions of potentially toxic metal ions.

Long-term accumulation of toxic heavy metals in the environment was a potential hidden danger. High energy consumption, complicated operation and low adsorption capacity were the disadvantages of most current adsorbents. This study used one-step modification of fly ash (FA) by low-temperature melting method with KOH as the activator to generate modified fly ash (KFA) with high adsorption capacity to remove heavy metals from aqueous solutions. Various characterization results revealed a destruction that occurred on the surface structure of adsorbent, 12 times increase in specific surface area, and metal ions were successfully adsorbed onto KFA surface. Furthermore, adsorption proceeded most favorably at pH of 5, the presence of ionic strength and co-existing cations significantly influenced the adsorption effects. The description of adsorption data was more suitable by pseudo-second-order kinetics and Langmuir isotherm models. And in single system at 25 °C, for Pb(II), Cu(II), and Cd (II), the qm were 337.41, 310.09 and 125.00 mg·g-1. However, in ternary system, the qm decreased for all three ions in the order Pb(II) > Cu(II) > Cd(II), which was different from the law in single system, and the Pb(II) adsorption was found to have a significant inhibited effect on adsorption of Cd(II) and Cu(II). The adsorption mechanisms including ion exchange, electrostatic attraction and complexation were revealed. And by exploring the bioaccessibility of absorbed heavy metals in four simulated digestive fluids, it was found that KFA could load heavy metal ions and enable their release in organisms and other aquatic environments, which provided the possibility for subsequent related studies. Therefore, KFA with low energy consumption and high adsorption capacity is equipped a prospective development space on removing heavy metals from wastewater.

Efficient removal of microplastics from aqueous solution by a novel magnetic biochar: performance, mechanism, and reusability.

Microplastics' (MPs) pollution removal from water bodies has become an urgent task to ensure water quality safety and water ecological security on a global scale. In this work, coprecipitation was employed to investigate the adsorption of MPs by magnetic biochar (MRB) prepared from agricultural waste rice husks in an aquatic system. The results showed that MRB can adsorb up to 99.96% of MPs in water; acidic conditions were favorable for the effective MPs' adsorption reaction, and competing anions had a greater effect on adsorption. The adsorption mechanism results revealed that the adsorption of MPs by MRB was a spontaneous process, and electrostatic attraction, surface complexation, hydrogen bonding and π-π interactions were present in the adsorption process. Furthermore, after the adsorption of MPs, MRB can be recovered by thermal treatment (500 °C) and still exhibits up to 90% MPs adsorption (after four uses). This work reveals that MRB is an inexpensive, efficient, and reusable nanoscale adsorbent for MPs pollution removal in water, which may provide new ideas for microplastic pollution control in the aqueous environment.

The role of available nitrogen in the adsorption of polystyrene nanoplastics on magnetic materials.

Several studies have been conducted on nanoplastics (NPs). However, few studies have investigated the complexity of the interactions between NPs and other aqueous pollutants in multi-solute media. In this study, the adsorption of polystyrene nanoplastics (PSNPs) on magnetic materials (MS) in the presence of available nitrogen (AN) was studied. The results demonstrated that the adsorbed amount of PSNPs increased in the presence of ammonium nitrogen (NH4+-N), whereas no significant difference was detected on the adsorbed amount of PSNPs using nitrate nitrogen (NO3--N) as a cosolute. The increase in the adsorbed amount of PSNPs was attributed to the formation of an MS-PSNPs-NH4+-N complex. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and zeta potential analyses indicated that the PSNPs with NH4+-N as a cosolute can be bound on the MS surfaces. Moreover, the change in the PSNPs amount adsorbed by MS depends on the valence state, electronegativity of the coexisting ions, and the surface properties and functional groups of PSNPs. Additionally, the ionic strength, dissolved organic matter, solution pH, metal cations and the subsequent release of MS-coated PSNPs and NH4+-N changed considerably in different aquatic systems and artificial nitrating fluids. Among different natural aquatic systems, the PSNPs adsorption on MS was excellent in lake water. The results indicate high potential for the attachment of PSNPs to MS in the presence of AN and further deepen the understanding of removing NPs using magnetic materials in aqueous systems with various coexisting contaminants.

Identifying strontium sources of flowback fluid and groundwater pollution using 87Sr/86Sr and geochemical model in Sulige gasfield, China.

Hydraulic fracturing technology has made unconventional oil and gas development economically viable; however, it can lead to potential environmental issues such as groundwater pollution. Strontium isotope (87Sr/86Sr) is considered as a sensitive tracer to indicate potential groundwater contamination. In this study, strontium (Sr) and 87Sr/86Sr sources of hydraulic fracturing flowback fluid are identified with 87 flowback fluid samples and 5 borehole core samples. High Sr concentrations and 87Sr/86Sr values were found in fracturing flowback fluid. The hydrogeochemistry evidence shows high Sr and 87Sr/86Sr in fracturing flowback fluid mainly comes from formation water with high ion concentrations, while Sr and 87Sr/86Sr of formation water develop in diagenesis and long term water-rock interaction (e.g., feldspar dissolution and clay mineral transformations) under the high temperature and pressure. A complete evaluation system was executed to assess the sensitivity of 87Sr/86Sr indicating potential pollution on groundwater. The mixing curves which 87Sr/86Sr combined with Sr and Cl were also established by mixing models to indicate groundwater pollution. The modeling results show mineral dissolution/precipitation and cation exchange have little impact on 87Sr/86Sr in the mixing process between fracturing flowback fluid and groundwater, which 87Sr/86Sr can identify contamination when only 0.89% of fracturing flowback fluid mixes with groundwater. Finally, the potential contamination pathways are discussed. It is highly unlikely fracturing flowback fluid contaminates groundwater and soil through upward migration, whereas leakage is a more prevalent pollution pathway.

Adsorption behavior of aged polybutylece terephthalate microplastics coexisting with Cd(II)-tetracycline.

Microplastics (MPs) are one of the emerging classes of pollutants that can be infiltrated into any aqueous solutions from disposed toxic metals and antibiotics, further exacerbating the potential biotoxicity of MPs. However, the research on the interaction between MPs and various pollutants is limited. Therefore, in this study, the changes in toxicity of polybutylece terephthalate (PBT) MPs were assessed following adsorption of heavy metals and antibiotics. The adsorption behavior of Cd(II) and tetracycline (TC) on ultraviolet (UV) light-aged PBT was investigated. The results demonstrated that the Cd(II) adsorption behavior could be described by the pseudo-second-order kinetic and Langmuir isothermal models, while the TC adsorption behavior has well fitted using Elovich and Sips models. The whole adsorption process occurred via either external diffusion or internal diffusion. The interactions between aged PBT and pollutants were evaluated under different environmental conditions, such as solution pH and the concentrations of dissolved organic matter and cations. The amounts of Cd(II) and TC adsorbed were higher in the competitive systems than the single solution, which might attribute to the formation of Cd(II)-TC complexes and aged PBT functional group changes. The results of two-dimensional correlation spectroscopy (2D-COS) describes the sequence of functional group transformation during the uptake of Cd(II)-TC by aged PBT in binary systems. These findings identify a strong interaction between aged PBT and contaminants, establishing the potential fate of aged MPs under natural aquatic environment conditions.

Moisture movement, soil salt migration, and nitrogen transformation under different irrigation conditions: Field experimental research.

Irrigation and fertilizer application can lead to significant changes in groundwater quality. In this study, a field irrigation experiment was carried out from April 9 to 23, 2021 under irrigation and fertigation conditions to understand the mechanisms of moisture movement, soil salt migration, and nitrogen transformation in the soil profile. Continuous in-situ monitoring and sampling of soil and irrigation water, as well as stable isotopes, chemical parameters, and soluble salt analyses, were performed in this research. The results showed that the time cost by the irrigation water in the vadose zone was about 5 h. The infiltrated irrigation water was accompanied by high concentrations of soluble salts, leached from the soil layers of 20-80 cm and 100-150 cm, which is associated with the leaching of Na+, Cl-, SO42-, and Ca2+ and the dissolution of minerals such as gypsum and halite. Furthermore, the variations in nitrogen concentrations (NH4+ and NO3-) in the soil profile suggested that fertilizer application was the main source of NO3- in the soil and groundwater, while irrigation was the biggest driving force for nitrogen transport and transformation in soil. The application of urea fertilizer can increase the content of ammonium nitrogen at the soil layer of 0-80 cm. This nitrogen form can be subsequently transformed to nitrate nitrogen during the water transport to the groundwater. The current study provides a strong scientific basis for the protection and management of groundwater and soil quality in agricultural areas.

A 3-year field study on lead immobilisation in paddy soil by a novel active silicate amendment.

Lead (Pb) is a toxic metal in industrial production, which can seriously threat to human health and food safety. Thus, it is particularly crucial to reduce the content of Pb in the environment. In this study, raw fly ash (FA) was used to synthesise a new active silicate materials (IM) employing the low-temperature-assisted alkali (NaOH) roasting approach. The IM was further synthesised to form zeolite-A (ZA) using the hydrothermal method. The physicochemical characteristics of IM and ZA amendments before and after Pb2+ adsorption were analysed using the Scanning electron microscope-Energy Dispersive Spectrometer (SEM-EDS), Fourier Transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) apparatuses. The results revealed the considerably change in the microstructure and functional groups of IM and ZA amendments, conducive to Pb2+ removal. Moreover, a 3-year field experiment revealed that the IM and ZA significantly improved the growth of rice and reduced available Pb by 21%-26.8% and 9.7%-16.9%, respectively. After 3 years of remediation, the Pb concentration of the rice grain reached the national edible standard (≤0.2 mg kg-1) of 0.171 mg kg-1 and 0.179 mg kg-1, respectively. Meanwhile, the concentration of acid-exchangeable Pb reduced, while those of reducible and residual fractions of Pb increased. There was no significant difference between the IM and ZA treatments. The potential mechanisms of remediation by the amendments were ion-exchange, complexation, precipitation, and electrostatic attraction. Overall, the results indicate that IM is suitable for the remediation of contaminated soil and promotes safe food production, and develops an environmentally friendly and cost-effective amendment for the remediation of polluted soil.

Remediation of cadmium contaminated soil by modified gangue material: Characterization, performance and mechanisms.

Nowadays, remediation of soil contaminated with potentially toxic metal is a great international concern. In this study, a novel modified gangue material (MGE) is synthesized from coal gangue (GE) through a low-temperature assisted with alkali roasting method, and is applied to the immobilization of cadmium (Cd2+) in contaminated soil. The various instruments (SEM-EDS, FTIR, XRD, TGA, and XPS) are employed to investigate the changes of microstructure and function of GE before and after the modification. The results showed that a large number of active groups (Si-O, Al-O, Fe-O, -OH, -CO, and -COOH) are observed on the surface of MGE, which is conducive to the removal of Cd2+. Besides, the adsorption kinetics, and isotherm models are introduced to analyze the potential adsorption mechanism, which suggesting that the adsorption behavior can be well fitted by pseudo-second-order and Langmuir models. The potential mechanisms of MGE include the ion exchange, complexation, electronic attraction, and precipitation. According to the pot experiment, the application of MGE can significantly improve the growth of pakchoi, and increase the pH of soils. Meanwhile, the content of available Cd2+ is reduced in the treatment with MGE, by a factor of 14.2%-29.8%. Correspondingly, the content of Cd2+ in different parts of pakchoi is also decreased. The study shows that the MGE can be strongly recommended as an efficient and safe amendment to stabilize Cd2+ in contaminated soil.

Effect and mechanisms of synthesis conditions on the cadmium adsorption capacity of modified fly ash.

In this study, modified coal fly ash (NMFA) was prepared by sodium hydroxide (NaOH) with low-temperature hydrothermal method. The differences of the ash to alkali mass ratio (5:3, 5:4, 5:5, 5:6), calcination temperature (100 â„ƒ, 200 â„ƒ, 300 â„ƒ), and calcination time (1 h, 3 h, 5 h) were investigated. The adsorption experiments obtained the optimal result with the ash to base ratio of 5:5, calcination temperature of 200 â„ƒ, and calcination time of 3 h, adsorbing 90.27 mg/g of Cd2+. The characterization results (SEM-EDS, FTIR, XRD, and XPS) also confirmed the effective adsorption of Cd2+ by NMFA. The functional groups of Si-O, Al-O, and Fe-O played an important role in Cd2+ removal. Meanwhile, the influences of dosage, different pH, and co-existing cations were also investigated. Quasi-secondary adsorption kinetics and Langmuir isotherm model were also referred to the Cd2+ adsorption by NMFA. Therefore, the good adsorption of NMFA-3 on Cd2+ provided new ideas for the safe utilization of fly ash and heavy metal purification in wastewater.

Effect of modified fly ash on environmental safety of two soils contaminated with cadmium and lead.

In this study, a low-temperature roasting and hydrothermal methods were used to modify the fly ash resulting in two new types of adsorption materials - modified fly ash (MFA) and artificial zeolite (ZE). These modified fly ashes, as well as a natural zeolite (ZO) were applied to two types of contaminated soils to explore their effects and mechanisms on the behavior of Cd and Pb through leaching column experiments. The bioavailable of Pb, Cd, pH, dissolved organic carbon (DOC), organic matter, as well as the microbial community changings were detected. The results showed that, 2% ZE has a significant stabilizing effect on Cd and the bioavailable fraction contents in Guanzhong (GZ) and Hunan (HN) soils decreased by 40.5% and 53.2%, respectively. However, for Pb, the 2% MFA showed a better result than that of ZE and ZO; the contents of bioavailable Pb in HN and GZ decreased by 48.3% and 30%, respectively. Furthermore, based on the Illumina NovaSep sequencing platform, 18 soil samples of GZ and HN were sequenced for microbial communities. As compared to the control blank(CK) treatment, the abundance of soil microbial communities was significantly improved in the amended soils.

Potential of a novel modified gangue amendment to reduce cadmium uptake in lettuce (Lactuca sativa L.).

In this study, the modified gangue (GE) was prepared by calcination at lower temperatures using potassium hydroxide (KOH) as the activating agent. The field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF) methods were employed to analyze the physicochemical characteristics of GE before and after the modification. Besides, the GE and commercial zeolite (ZE) were compared in the remediation of Cd-contaminated soil in field experiments. The results showed that both the GE and ZE had positive effects on the stabilization of Cd, decreasing the available Cd by 21.2-33.9% and 22.1-28.2%, respectively, while no significant difference was observed between the two amendments, indicating that the modification of GE was successful. Moreover, the application of GE decreased the Cd mobilization and uptake in lettuce shoot and root by 54.9-61.5% and 9.3-13.2%, respectively, and at the same time, the bio-available Cd decreased by 20.9-34.5%. Moreover, with the addition of GE, activities of urease and alkaline phosphatase increased in soil, while the peroxidase and superoxide dismutase activities were notably reduced in plants. Therefore, GE could be used as an effective amendment for the alleviation of Cd accumulation and toxicity, and thereby improve food safety.

Removal of Cadmium from Contaminated Groundwater Using a Novel Silicon/Aluminum Nanomaterial: An Experimental Study.

Cadmium (Cd) is a harmful element to human health and biodiversity. The removal of Cd from groundwater is of great significance to maintain the environmental sustainability and biodiversity. In this work, a novel low-temperature roasting associated with alkali was applied to synthesize an eco-friendly adsorbent using coal fly ash. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence, and X-ray photoelectron spectroscopy were applied to analyze the physical and chemical characteristics of the adsorbent. The experiments show that a significant improvement in specific surface area and activity of adsorbent was observed in this study. The functional groups of Na-O and Fe-O were verified to be beneficial in the removal of Cd2+. The material capacity to adsorb Cd2+ was considerably improved, and the maximum uptake capacity was 61.8 mg g-1 for Cd2+ at 25 °C. Furthermore, pH and ionic strength play critical roles in the adsorption process. The Langmuir and pseudo-second-order models can appropriately describe the adsorption behavior, and the enhanced adsorption ability of Cd2+ by modified coal fly ash was attributed to ion-exchange, co-precipitation, and complexation. Higher sorption efficiency was maintained after two regeneration cycles. These results offer valuable insights to develop high-performance adsorbent for Cd2+ removal.

Potential of using a new aluminosilicate amendment for the remediation of paddy soil co-contaminated with Cd and Pb.

Cadmium (Cd) and lead (Pb) are toxic heavy metals that impact human health and biodiversity. Removal of Cd/Pb from contaminated soils is a means for maintaining environmental sustainability and biodiversity. In this study, we applied a newly modified material fly ash (NA), zeolite (ZE), and fly ash (FA) to the paddy soils and evaluated the effects of Cd/Pb accumulation in rice via a one-year field experiment. The results showed that the application of NA and ZE enhanced the soil pH and nutrients to a large extent and reduced the availability of Cd/Pb in soil. The Cd and Pb concentrations in rice grains decreased by 32.8% and 62.9%, respectively, with the NA treatments. Similarly, the application of ZE reduced the Cd and Pb concentrations in rice grains by a factor of 27.9% and 63.5%, respectively, which indicates that the amendments can promote the transfer of Cd and Pb from acid-exchangeable fraction to oxidizable and residual fractions. The Cd/Pb showed a significant positive correlation to other metal ions and a negative correlation to the nutrients. Generally, the application of NA and ZE was effective in reducing Cd/Pb accumulation and improving rice yield. Moreover, the NA was more cost-effective than ZE. Hence, this study proves that NA may be a better amendment for remediation of Cd/Pb contaminated soils.

Optimization of preparation technology for modified coal fly ash and its adsorption properties for Cd2.

This work focused on preparation a novel adsorbent from coal fly ash (CFA) and solid alkali (NaOH) by low temperature roasting method. The modification parameters (mass ratio, calcination time and temperature) were specifically studied and optimized. The adsorption experiment results indicated that, the adsorption amounts of Cd2+ were enhanced with the decreasing mass ratio of CFA and NaOH, and the adsorption amounts of Cd2+ were 32.44, 31.66, 38.5 and 79.85 mg/g at the mass ratio (CFA/NaOH) of 5:5, 5:6, 5:7 and 5:8, respectively. The higher modification temperature was not conducive to the removal of Cd2+, as the adsorption capacities of Cd2+ calculated were 62.42, 69.53 and 41.73 mg/g at the reaction temperature of 250, 300 and 400 ℃. Interestingly, the modification time slightly effects on the adsorption ability of materials. According to the results, the optimum modification condition for preparing adsorbents were CFA/NaOH mass ratio of 5:8 and calcined at 300 ℃ for 3 h. Moreover, the influence of pH, ionic strength and Glycine concentration on Cd2+ uptake were also investigated. The kinetic, adsorption isotherm and thermodynamics models were applied to investigate the adsorption mechanism, which indicated that the adsorption process was better fitted by Langmuir and pseudo-second-order models.

Potential of enhancing the phytoremediation efficiency of Solanum nigrum L. by earthworms.

Contamination of the soil by Cadmium (Cd) is emerged as a critical environmental problem in China due to current urbanization and industrial activities that hinder the sustainable future development of agriculture. In this study, a system combined by earthworm and Solanum nigrum L. (S. nigurm) was designed for remediation of Cadmium from contaminated soils. The present study revealed that application of earthworm enhanced the biomass of S. nigrum by 61.71%, maxim; the Cd concentrations in the aboveground part of S. nigrum enhanced 35.8% when 50 g earthworm was added into each pot; the addition of earthworm also have some effect on the bio-concentration factor (BF) of S. nigrum while no effect was detected on the bio-transfer factor (TF). In addition, considering the accumulation of Cd by earthworm, the total amount of Cd extracted by the combined system enhanced 57.7% at least and 264.6% at the most, compared to the Cd extraction amount of S. nigrum alone. Generally, according to this study, the earthworm-S. nigrum system has the potential to be used for the remediation of Cd contaminated soils.

Potential of removing Cd(II) and Pb(II) from contaminated water using a newly modified fly ash.

Modified fly ash was prepared through low-temperature roasting method using NaOH as activator. The techniques of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and the X-ray diffraction (XRD) were introduced to analyze the chemical and physical performance of samples, respectively. It was found that a significant improvements in activity and specific surface area of adsorbent. This work systematically reported the uptake performances of modified materials for single and two mixed toxic cations Pb(II) and Cd(II). The results unveiled that pseudo-second-order model was suitable to analyze the adsorption process. The adsorption process were better fitted by Langmuir model and the maximum uptake capacities were 126.55 and 56.31 mg g-1 for Pb(II) and Cd(II) in single system at 298 K, respectively. Additionally, in mixed solution, the maximum uptake capacity reduced to 120.48 and 36.10 mg g-1 under the same adsorption conditions. Competitive adsorption results demonstrated that adsorption ability was restricted by other metal ions, as while as, the binding affinity of two cations followed the order of Pb(II)>Cd(II). Meanwhile, the co-existed cations as Ca(II), Mg(II) Na(I) and K(I) had antagonistic effects on the uptake of Cd(II) and Pb(II). The results indicate that the modified fly ash was a low-cost and effective adsorbent for the cleaning up metal ions in wastewater, which has a promising application prospect.

Possibility of removing cadmium pollution from the environment using a newly synthesized material coal fly ash.

Coal fly ash (FA) is a solid waste produced in coal combustion. This study focused on the removal of Cd2+ from wastewater by a newly synthesized adsorbent material, the low-temperature and sodium hydroxide-modified fly ash (SHM-FA). The SEM and BET analyses of SHM-FA demonstrated that the adsorbent was porous and had a huge specific surface area. The XRF, XRD, FTIR and TGA characterization showed that SHM-FA has an amorphous structure and the Si-O and Al-O in the fly ash dissolved into the solution, which improved the adsorption capacity of Cd. The results indicated that SHM-FA has desired adsorption performance. The adsorption performance was significantly affected by the dosage, starting pH, Cd2+ initial concentrations, and temperature, as well as adsorption time. In the optimal conditions, the removal efficiency and adsorption capacity of Cd2+ by SHM-FA were 95.76% and 31.79 mg g-1, respectively. The experiment provided clearly explained adsorption kinetics and isotherms. And the results confirmed that the adsorption behavior was well described by the pseudo-second-order kinetic and Langmuir isotherm model, which means that the adsorption of Cd2+ was controlled by SHM-FA through surface reaction and external diffusion process. In addition, the recycling of SHM-FA for reuse after Cd2+ adsorption showed high removal efficiency up to six times of use. Therefore, it can be concluded that SHM-FA is a low-cost adsorbent for Cd2+ removal from wastewater.