Arsenic selective adsorption using a nanomagnetic ion imprinted polymer: Optimization, equilibrium, and regeneration studies

Application Prospect of Ion-Imprinted Polymers in Harmless Treatment of Heavy Metal Wastewater

With the rapid development of industry, the discharge of heavy metal-containing wastewater poses a significant threat to aquatic and terrestrial environments as well as human health. This paper provides a brief introduction to the basic principles of ion-imprinted polymer preparation and focuses on the interaction between template ions and functional monomers. We summarized the current research status on typical heavy metal ions, such as Cu(II), Ni(II), Cd(II), Hg(II), Pb(II), and Cr(VI), as well as metalloid metal ions of the As and Sb classes. Furthermore, it discusses recent advances in multi-ion-imprinted polymers. Finally, the paper addresses the challenges faced by ion-imprinted technology and explores its prospects for application.

Metformin-modified polyethersulfone magnetic microbeads for effective arsenic removal from apatite soil leachate water

Arsenic is the hazardous species and still is the global challenge in water treatment. Apatite soil is highly rich in arsenic species, and its mining presents various environmental issues. In this study, novel magnetic microbeads as adsorbent were developed for the elimination of hazardous arsenic ions from apatite soil's aqueous leachate before discharging into environment. The microbeads were fabricated with metformin polyether sulfone after being doped with zero-valent iron (Met-PES/ZVI). The microbeads were characterized using various techniques, including FTIR, XRD, SEM-EDX, VSM, and zeta potential analysis. The developed adsorbent demonstrated a significant elimination in arsenic in aqueous leachate, achieving 82.39% removal after 30 min of contact time, which further increased to 90% after 180 min of shaking. The kinetic analysis revealed that the pseudo-second-order model best represented the adsorption process. The intra-particle diffusion model indicated that the adsorption occurred in two steps. The Langmuir model (R2 = 0.991), with a maximum adsorption capacity of 188.679 mg g-1, was discovered to be the best fit for the experimental data as compared Freundlich model (R2 = 0.981). According to the thermodynamic outcome (ΔG < -20 kJ/mol), the adsorption process was spontaneous and involved physisorption. These findings demonstrate the potential of magnetic Met-PES/ZVI microbeads as an efficient adsorbent for the removal of arsenic from apatite soil aqueous leachate.

Abalone shell-based magnetic macroporous hydroxyapatite microspheres with good reusability for efficient dye adsorption

Azo dye methyl orange (MO) and shell rotting cause great environmental pollution. Most of the common dye adsorbents are difficult to produce, not environmentally friendly and it is always difficult to utilize the shell resources effectively. In this study, shell-based economical and environmentally friendly magnetic hydroxyapatite microsphere adsorbents (Fe3O4 @SiO2/HAP) were developed for the removal of MO from simulated wastewater by sol-gel and hydrothermal synthesis methods. The effects of solution pH, initial concentration, adsorption time and system temperature on the adsorption effect were investigated, and the repeat recovery performance was explored. The equilibrium adsorption data follow the Freundlich isotherm and pseudo-second-order kinetic curves, and the analysis indicates that the adsorption process is spontaneously exothermic. The adsorption capacities of MO were up to 94.48% and 88.94%, under the acidic environment of pH = 4, respectively, and had good recycling performance. The results provide a high-value utilization pathway for waste shell resources and focus on the removal of azo dyes. This is expected to provide new development ideas for the environmental hazards caused by acid dye wastewater discharged into rivers and oceans, as well as the problems of soil pollution and resource waste caused by weathering and corrosion of shells.

Simultaneous Cr (VI) reduction and diazinon oxidation with organometallic sludge formation under photolysis: kinetics, degradation pathways, and mechanism

In this study, simultaneous removal of an organic matter (diazinon, DIZ) and an inorganic substance (chromium, Cr) was used. Breaking down of organic matter by UV irradiation produces various radicals, including sulfides, carboxyl, hydroxyl, hydrated electrons, and various organic radicals that are highly reactive and help us to precipitation inorganic substance (Cr). The optimal condition was 30:1 DIZ:Cr molar ratio, pH 9, and about 100% and 82.3% of DIZ and Cr were obtained in 30 min. Cr deposition was very slow at first. After the destruction of the DIZ structure, Cr deposition began, and various types of sludge with disturbed properties were formed. These sledges were analyzed by FTIR analysis and showed that green sludge could be chromium (III) hydroxide; brown sludge due to chromium (III) hydroxide, tiny green crystals from chromium (III) oxide, red brick from chromium (II) acetate chromium trioxide, as well as black sludge caused by chromium oxide were identified. In UV/DIZ/Cr process, kobs and robs range obtained 0.33-0.15 and 16.8-23.4 $ with both Cr and DIZ concentration increased from 50 to 150 mg L-1. Also, EEO for Cr precipitation was 24.65 to 5.74 and for DIZ 12.54 to 4.73 (kwh m-3). Depending on the amount of energy consumption, TCS was 37.19 to 10.47 for Cr precipitation and 4.46 to 1.25 $. It is important to note that when both pollutants are exposed to ultraviolet light, more energy and cost are generally required from UV/DIZ process and less than of UV/Cr process. But it should be noted that in fact 50 mg L-1 of chromium and 50 mg L-1 of DIZ are being removed at the same time. In UV/DIZ and UV/Cr processes that are exposed to ultraviolet radiation alone, only one of them is removed. Also, when these two pollutants are being removed at the same time, the total amount of energy is much less than the total energy consumption of the pollutants one by one.

Arsenic(III) and Arsenic(V) Removal from Water Sources by Molecularly Imprinted Polymers (MIPs): A Mini Review of Recent Developments

The present review article summarizes the recent findings reported in the literature with regard to the use of molecularly imprinted polymers for the removal of arsenic from water and wastewater. MIPs are polymers in which a template is employed in order to enable the formation of recognition sites during the covalent assembly of the bulk phase, via a polymerization or polycondensation process. The efficiency of both arsenic species and the mechanism of removal are highlighted. The results have shown that under certain conditions, MIPs demonstrated arsenic sorption capacities of up to 130 mg/g for As(V) and 151 mg/g for As(III), while the regeneration ability was found to reach up to more than 20 cycles. The overall results showed that further development of MIPs could result in the formation of promising adsorbents for arsenic removal from waters. The use of MIPs for the removal not only of arsenic but also other inorganic contaminants is considered a very important topic, with great potential in terms of future applications in water treatment. The main advantage of these materials is that they are very selective toward the contaminant of interest. This enhanced selectivity is attributed to the incorporation of specific templates, which can then adsorb the contaminant of interest almost exclusively. Therefore, the main problem in adsorption processes is the competition for adsorption sites by other water components, for example, phosphates, nitrates, carbonates, and sulfates, which can be circumvented by the use of MI-type adsorbents.

Magnetic Ion Imprinted Polymers (MIIPs) for Selective Extraction and Preconcentration of Sb(III) from Environmental Matrices

Antimony(III) is a rare element whose chemical and toxicological properties bear a resemblance to those of arsenic. As a result, the presence of Sb(III) in water might have adverse effects on human health and aquatic life. However, Sb(III) exists at very ultra-trace levels which may be difficult for direct quantification. Therefore, there is a need to develop efficient and reliable selective extraction and preconcentration of Sb(III) in water systems. Herein, a selective extraction and preconcentration of trace Sb(III) from environmental samples was achieved using ultrasound assisted magnetic solid-phase extraction (UA-MSPE) based on magnetic Sb(III) ion imprinted polymer-Fe3O4@SiO2@CNFs nanocomposite as an adsorbent. The amount of antimony in samples was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The UA-MSPE conditions were investigated using fractional factorial design and response surface methodology based on central composite design. The Sb(III)-IIP sorbent displayed excellent selectivity towards Sb(III) as compared to NIIP adsorbent. Under optimised conditions, the enrichment factor, limit of detection (LOD) and limit of quantification (LOQ) of UA-MSPE/ICP-OES for Sb(III) were 71.3, 0.13 µg L-1 and 0.44 µg L-1, respectively. The intra-day and inter-day precision expressed as relative standard deviations (%RSDs, n = 10 and n = 5) were 2.4 and 4.7, respectively. The proposed analytical method was applied in the determination of trace Sb(III) in environmental samples. Furthermore, the accuracy of the method was evaluated using spiked recovery experiments and the percentage recoveries ranged from 95-98.3%.

Significant improvement on selectivity and capacity of glycine-modified FeCo-layered double hydroxides in the removal of As (V) from polluted water

A series of novel Fe/Co layered double hydroxides modified with glycine (named as FeCo-LDH@G) were prepared and served as high-performance adsorbents for As (V). With a Fe/Co mole ratio of 1:1, the Fe_0·02Co_0.02-LDH@G adsorbents achieved significant improvements on the adsorption selectivity and capacity for As (V). The As (V) adsorption by Fe_0·02Co_0.02-LDH@G follows Langmuir isotherm model and pseudo-second-order kinetics model. The maximum adsorption capacity is 820 mg g^-1 and the equilibrium reaches in 120 min. Under the assistance of electrochemical devices, the Fe_0·02Co_0.02-LDH@G adsorbent was regenerated and the adsorption capacity for As (V) was dropped only about 13.41% in 5 cycles. These excellent performances make Fe_0·02Co_0.02-LDH@G as promising As (V) adsorbents for commercial wastewater treatments.

Magnetic field assisted adsorption of pollutants from an aqueous solution: A review

The magnetic field is a special substance that exists objectively and transmits the magnetic force between objects. Magnetic fields (MFs) are gradually attracting attention as a facile, universal adsorption enhancement method, especially under the condition of low concentration of pollutants. By adjusting the type and parameters of the magnetic field, enhancement of adsorption capacity, rate and selectivity can be targeted. Many studies have focused on the adsorbent separation based on magnetic properties under MF assistant, and no review have come up in recent years on the pollution enhanced-adsorption technique using MFs. The present review brings out a series of magnetic field and summarizes adsorption-assisted enhancement mechanism of MFs in different situations. This review article aimed at helping researchers obtain quick ideas of MFs and application for pollutant adsorption.