Preparation and properties of GO-based lanthanum ion-imprinted polymer, La-IIP-MAA/Fe3O4-GO

Preparation of ion imprinted EDTA modified chitosan-magnetic graphene oxide for selective recovery and adsorption mechanism of Ce(III)

Selective recovery of rare earth elements (REEs) from environmental waste is strategically significant. Herein, Ce(III) imprinted EDTA modified chitosan-magnetic graphene oxide (IIP-EDTA-CS-MGO) was prepared for selective recovery of Ce(III). Furthermore, adsorption mechanism was clarified based on versatile adsorption fittings and spectroscopic tests. Result presents, adsorption reaches its peak at pH = 7 in 25 min with maximum adsorption capacity 353.28 mg·g-1. Functional groups C(=O)NH, CN and C-O-C in IIP-EDTA-CS-MGO provide heterogeneous affinity for Ce(III) to induce chemical adsorption. Thermodynamic calculation suggests spontaneous, endothermic and entropy increasing adsorption. Owing to Ce(III) imprinting, IIP-EDTA-CS-MGO demonstrates selectivity coefficients 3.09, 3.19, 14.10, 12.65 towards Ce(III) for binary solutions Ce/Eu, Ce/Dy, Ce/Cu, Ce/Cr, respectively. By virtue of its paramagnetic property, IIP-EDTA-CS-MGO can be readily recovered via magnetic separation for cyclic adsorption, thereby retaining adsorption quantity 116.58 mg·g-1 for Ce(III) in five consecutive cycles. This work provides a new approach for fabricating magnetic bio-adsorbent towards selective recovery of Ce(III).

Fabrication of sodium alginate-doped carbon dot composite hydrogel and its application for La (III) adsorption and enhanced the removal of phosphorus

Adsorption is an effective method for the removal of hazardous substances from wastewater. In this work, a low-cost and environmental-friendly composite hydrogel material of sodium alginate doped with nitrogen doped carbon dots (SA@NCDs) was fabricated by impregnation for lanthanide and enhanced phosphorus adsorption in wastewater. The effects of NCDs doping amount, dosage, pH, initial solution concentration, adsorption time and temperature on the process of La (III) adsorption by SA@NCDs were investigated. The adsorption isotherms fitted to Langmuir isotherm model (R2 = 0.9970-0.9989) and the adsorption kinetics followed pseudo-second-order kinetic model (R2 = 0.9992). The maximum adsorption capacity of the adsorbent for La (III) was 217.39 mg/g according to the Langmuir model at 298.15 K. After five cycles, the removal efficiency of La (III) adsorbed by SA@NCDs was still 85.1%. Moreover, the loaded La (III) enhanced the adsorption of phosphorus. The La (III)-SA@NCDs-5 hydrogel adsorbent greatly improved the adsorption capacity for phosphorus compared with the La (III)-free adsorbent, and the adsorption amount can reach 9.64 mg-P/g. The SA@NCDs complex hydrogels for rare earth adsorption were prepared by introducing NCDs rich in amino group into SA hydrogels. The introduction of NCDs increases the adsorption sites of hydrogels, and also overcomes the problem that NCDs itself is difficult to recover in wastewater treatment applications. The lanthanide adsorbed material has a stable structure and can be used to remove phosphorus to deal with waste using the waste. It indicates the SA@NCDs hydrogel composite adsorbent have good potential for wastewater treatment.

Synthesis of nanostructured novel ion-imprinted polymer for selective removal of Cu2+ and Sr2+ ions from reverse osmosis concentrated brine

This study aims to prepare an ion-imprinted polymer (IIP) using copper sulfate as a template and potassium persulfate as an initiator to selectively adsorb copper ions (Cu²⁺) from aqueous solutions and in an attempt to also test its applicability for removing strontium ions (Sr²⁺). The prepared polymer was denoted by IIP-Cu. Various physical and chemical characterizations were performed for the prepared IIP-Cu. The scanning electron microscopy and transmission electron microscopy analyses confirmed the cavities formed after the removal of the template. It also indicated that the IIP-Cu had a rough and porous topology. The X-ray photoelectron spectroscopy confirmed the successful removal of the Cu template from IIP-Cu. The Brunauer-Emmet-Teller revealed that the surface area of IIP-Cu is as high as 152.3 m²/g while the pore radius is 8.51 nm. The effect of pH indicated that the maximum adsorption of Cu²⁺ was achieved at pH 8 with 98.7%. Isotherm studies revealed that the adsorption of Cu²⁺ was best explained using Langmuir models with a maximum adsorption capacity of 159 mg/g. The effect of temperature revealed that an increase in temperature had an adverse impact on Cu²⁺ removal from the aqueous solution, which was further confirmed by thermodynamic studies. The negative value of standard enthalpy change (-4.641 kJ/mol) revealed that the adsorption of Cu²⁺ onto IIP-Cu was exothermic. While the continuous increase in Gibbs free energy from -6776 kJ/mol to -8385 kJ/mol with the increase in temperature indicated that the adsorption process was spontaneous and feasible. Lastly, the positive value of the standard entropy change (0.023 J/mol.K) suggested that the Cu²⁺ adsorption onto IIP-Cu had a good affinity at the solid-liquid surface. The efficiency of the prepared IIP-Cu was also tested by studying the adsorption capacity using Sr²⁺ and real brine water. The results revealed that IIP-Cu was able to remove 63.57% of Sr²⁺ at pH 8. While the adsorption studies revealed that the experiment was best described using the Langmuir model with a maximum adsorption capacity of 76.92 mg/g. Additionally, IIP-Cu was applied in a real brine sample, which consisted of various metal ions. The highest percentage of Cu²⁺ removal was 90.6% and the lowest was 65.63% in 1:4 and 1:1 brine ratios, respectively. However, this study indicates the successful application of IIP-Cu in a real sample when it comes to the effective and efficient removal of Cu²⁺ in a solution consisting of various competing ions.

Polyaminophosphoric Acid-Modified Ion-Imprinted Chitosan Aerogel with Enhanced Antimicrobial Activity for Selective La(III) Recovery and Oil/Water Separation

In this study, polyaminophosphoric acid (PA)-functionalized ion-imprinted chitosan (CS) aerogel was fabricated for the first time, exhibiting good antibacterial property for selective La(III) recovery and oil/water separation. The as-prepared PA-CS-IIA-2 shows a remarkable adsorption capacity of 114.6 mg/g toward La(III) and high selectivity in the competitive adsorption systems, which is attributed to its abundant imprinting sites and surface functional groups. Benefiting from the amphiphilic property, the PA-CS-IIA-2 also exhibits an excellent adsorption performance for the extractant, oils, and organic solvents. Besides, the PA-CS-IIA-2 presents excellent regeneration and reusability characteristics. Moreover, compared with CS, the PA-CS-IIA-2 exhibits a significantly improved antibacterial activity originating from the PA component. Most importantly, the PA-CS-IIA-2 aerogel is capable of removing multiple pollutants all together and effectively inhibiting bacteria in the complex wastewater environments. Therefore, this study paves the way for developing high-performance rare-earth capture materials with multiple functions to meet diverse applications.

Nanomaterials-Based Ion-Imprinted Electrochemical Sensors for Heavy Metal Ions Detection: A Review

Heavy metal ions (HMIs) pose a serious threat to the environment and human body because they are toxic and non-biodegradable and widely exist in environmental ecosystems. It is necessary to develop a rapid, sensitive and convenient method for HMIs detection to provide a strong guarantee for ecology and human health. Ion-imprinted electrochemical sensors (IIECSs) based on nanomaterials have been regarded as an excellent technology because of the good selectivity, the advantages of fast detection speed, low cost, and portability. Electrode surfaces modified with nanomaterials can obtain excellent nano-effects, such as size effect, macroscopic quantum tunneling effect and surface effect, which greatly improve its surface area and conductivity, so as to improve the detection sensitivity and reduce the detection limit of the sensor. Hence, the present review focused on the fundamentals and the synthetic strategies of ion-imprinted polymers (IIPs) and IIECSs for HMIs detection, as well as the applications of various nanomaterials as modifiers and sensitizers in the construction of HMIIECSs and the influence on the sensing performance of the fabricated sensors. Finally, the potential challenges and outlook on the future development of the HMIIECSs technology were also highlighted. By means of the points presented in this review, we hope to provide some help in further developing the preparation methods of high-performance HMIIECSs and expanding their potential applications.

Water-Recyclable Chitosan-Based Ion-Imprinted Thermoresponsive Hydrogel for Rare Earth Metal Ions Accumulation

The demand for rare earth metal increases rapidly in the modern high-tech industry and therefore the accumulation of rare earth metal ions from an aqueous environment becomes a significant concern worldwide. In this paper, a water-recyclable chitosan-based La³⁺-imprinted thermoresponsive hydrogel (CLIT) was prepared to accumulate La³⁺ from solution. The CLIT was characterized by DSC, FITR, Raman spectroscopy, XPS, and SEM, which revealed obvious reversible thermosensitivity and imprinted sites of La³⁺ ions. An adsorption capacity of 112.21 mg/g to La³⁺ ions was achieved on CLIT under its optimum adsorption conditions (pH 5, 50 °C, 60 min). The adsorption could be well illustrated by second-order kinetics and Freundlich isotherm models. The La³⁺-adsorbed CLIT could be recycled only by rinsing with 10 °C cold water, with a desorption rate of 96.72%. After ten cycles of adsorption-desorption, CLIT retained good adsorption capability. In the solution containing six ions, the adsorption coefficients k_La3+/Mn+ of CLIT were 2.04–3.51 times that of non-imprinted hydrogel, with k_La3+/Y3+, k_La3+/Gd3+, k_La3+/Al3+, k_La3+/Fe3+ and k_La3+/Cu2+ being 1.67, 2.04, 3.15, 2.72 and 4.84, respectively.