Facile synthesis of sodium lignosulfonate/polyethyleneimine/sodium alginate beads with ultra-high adsorption capacity for Cr(VI) removal from water

Preparation and modification of polymer microspheres, application in wastewater treatment: A review

The removal of various pollutants from water is necessary due to the increasing requirements for the removal of various pollutants from wastewater and the quality of drinking water. Polymer microspheres are regarded as exemplary adsorbent materials due to their high adsorption efficiency, excellent adsorption performance, and ease of handling. Herein, the advantages and disadvantages of different preparation methods, modifications, applications and the current research status of polymer microspheres are summarized at large. Furthermore, the enhanced performance of modified composite microspheres is emphasized, including adsorption efficiency, thermal stability, and significant improvements in physical and chemical properties. Subsequently, the current applications and potential of polymeric microspheres for wastewater treatment, including the removal of inorganic and organic pollutants, heavy metal ions, and other contaminants are summarized. Finally, future research directions for polymer microspheres are proposed, outlining the challenges and solutions associated with the application of polymer microspheres in wastewater treatment.

Recyclable chitosan adsorbent: Facile functionalization strategy, excellent removal capacity of dyes and adsorption mechanism

The development of chitosan-based adsorbents with facile preparation, high adsorption performance and reusability for the removal of contaminant dyes remains a persistent challenge. To overcome this challenge, herein, we have developed a novel and extremely facile one-step strategy by which a new high-performance chitosan/polyethyleneimine/polyethylene glycol diglycidyl ether adsorbent (named as CC/PEI/PGDE) has been successfully fabricated via direct functionalization of CC by PEI at ambient temperature followed by subsequent freeze-drying. The Box-Behnken Design was employed to optimize the concentrations of adsorbent components. Attractively, this adsorbent exhibit outstanding adsorption performances to congo red (RED), acid blue-25 (BLUE) and amino black-10B (BLACK) with 2901 mg g-1 (90.9 %), 3434 mg g-1 (90.9 %), and 1438 mg g-1 (90.1 %) of adsorption capacities (removal efficiencies), respectively, and maintains nearly the same adsorption behaviors to original adsorbent even after 6 cycles of adsorption-desorption processes. Meanwhile, three kinetic models, three isothermal models, and the Vant Hoff model are employed to further investigate the adsorption behaviors of RED, BLUE, and BLACK dyes by CC/PEI/PGDE. The results from SEM, EDS, BET, FT-IR, pHZPC and XPS confirm that hydrogen bond interactions and electrostatic attractions play crucial roles in facilitating dyes adsorption by CC/PEI/PGDE. It is expected that this work can bring forward a new perspective for the facile design of high-performance adsorbent for removing anionic dyes from wastewater.

Zinc oxide nanoparticles encapsulated in alginate beads: a promising and recyclable adsorbent for simultaneous uptake of toxic metals

Heavy metal toxicity is a known problem and various methods are used for treatment. Adsorption has some advantages and it would be promising if environmentally friendly and cheap materials were utilized. Alginate and zinc oxide nanoparticles were selected and composite alginate beads were used for the removal of mixed metals from aqueous solutions. Batch and column experiments were conducted to determine some parameters' effects and the adsorbent's real application potential. According to the batch experiments, zinc oxide nanoparticles to alginate ratio of 0.5 g g-1, and pH levels nearby to the neutral range led to better metal removals. 0.5 ml min-1of flow rate supplied better metal removal efficiencies in columns, with the highest treatment as 86% of Pb2+. Acid treatment can be successfully applied for the regeneration of the adsorbent, at least three times only with a 4% reduction in the adsorption efficiency. Heavy metal uptake was compatible with the pseudo 2nd order model indicating chemisorption as a dominant mechanism. Also, the intraparticle diffusion model illustrated adsorption might govern more than one step. The Langmuir model had the best fit and suggested monolayer covering for Pb2+, 76.3 mg g-1. Alginate-based nanocomposite beads were useful for mixed metal removal and could be used.

Sodium alginate based adsorbent: Facile fabrication, extraordinary removal efficacy of anionic dyes and adsorption mechanism

Eco-friendly and renewable sodium alginate, as a potential alternative to fossil resources, has attracted considerable attention in wastewater treatment field. Herein, we develop a SA/PEI/PEG (sodium alginate/polyethyleneimine/polyethylene glycol diglycidyl ether) adsorbent in which SA was functionalized by PEI/PEG via a facile but effective strategy of one-pot gelation of aqueous SA/PEI/PEG solution. Systematic investigations were accomplished to explore the effects of adsorbent factors on the adsorption performances of the adsorbent towards the anionic dyes CR (congo red), AB-10B (amido black-10B), and AB-25 (acid blue-25). Strikingly, the SA/PEI/PEG exhibited exceptional adsorption performance to CR (2782 mg g-1, 90.6 %), AB-10B (1369 mg g-1, 90.9 %) and AB-25 (4221 mg g-1, 92.6 %) at 30 °C, pH = 3, 200 r min-1 and oscillated 24 h, and demonstrating exceptional reusability after six cycles of adsorption-desorption cycles. Furthermore, the three kinetic, four isothermic and one thermodynamic models were used to investigate the adsorption behaviors of the adsorbent towards these dyes. The possible adsorption mechanism is suggested: Hydrogen bond interactions and electrostatic attractions between SA/PEI/PEG and the dyes primarily contribute to exceptional adsorption capacity. The SA/PEI/PEG adsorbent endowed with easy fabrication, extraordinary adsorption capacity and excellent reusability promises potential application prospects in wastewater purification industry.

Recent advances in alginate-based composite gel spheres for removal of heavy metals

The discharge of heavy metal ions from industrial wastewater into natural water bodies is a consequence of global industrialisation. Due to their high toxicity and resistance to degradation, these heavy metal ions pose a substantial threat to human health as they accumulate and amplify. Alginate-based composite gels exhibit good adsorption and mechanical properties, excellent biodegradability, and non-toxicity, making them environmentally friendly heavy metal ion adsorbents for water with promising development prospects. This paper introduces the basic properties, cross-linking methods, synthetic approaches, modification methods, and manufacturing techniques of alginate-based composite gels. The adsorption properties and mechanical strength of these gels can be enhanced through surface modification, multi-component mixing, and embedding. The main production processes involved are sol-gel and cross-linking methods. Additionally, this paper reviews various applications of alginate composite gels for common heavy metals, rare earth elements, and radionuclides and elucidates the adsorption mechanism of alginate composite gels. This study aimed to provide a reference for synthesising new, efficient, and environmentally friendly alginate-based adsorbents and to contribute new ideas and directions for addressing the issue of heavy metal pollution.

Selective removal of thallium from water by MnO2-doped magnetic beads: Performance and mechanism study

Aqueous thallium has posed an increasing threat to environment as human's intensified activities in mining, refining, process and discharge. Remediation on thallium pollution has been of up-most importance to water treatment. In present work, MnO2 and magnetic Fe3O4 have been implanted to sodium alginate (SA) in presence of carboxyl methyl cellulose (CMC), and the resultant beads consisted of SA/CMC/MnO2/Fe3O4 were characterized. The materials were applied to treatment of Tl-contaminated water as adsorbent in lab. The removal results revealed that the adsorption capacity reached 38.8 mg (Tl)·g (beads)-1 and almost 100 % removal efficiency was achieved. The residual Tl was below 0.1 μg·L-1, meeting the discharge standard regulated in China. The kinetic adsorption was better described as a pseudo-second-order and three-step intra-particle diffusion model. Freundlich isotherm was well fitted the experimental data. The absorbent shown an excellent competitive specificity (KTl/M: ∼104!) over common hazardous ions Cu2+, Cd2+, Co2+, Pb2+ and Cr3+, as well as naturally abundant K+ and Na+ (KTl/M: 10-102) in mimic environmental conditions. Regeneration and reusability of the absorbent was also verified by five absorption-desorpotion cycles. XPS results revealed that a redox reaction between Mn4+ with Tl+, and an ion exchange of H+ (-O-Fe) and Tl+ were assumed to be main process for the specific capturing. This study provided an efficient SA/CMC/MnO2/Fe3O4 composite beads that could be a promising adsorbent for Tl-polluted water treatment.

Novel soy protein isolate/sodium alginate-based functional aerogel for efficient uptake of organic dye from effluents

In response to the increasing global concern regarding water pollution, there is a growing demand for the development of novel adsorbents capable of effectively eliminating hazardous organic pollutants from effluents. In this study, we present a functional soy protein isolate (SPI)/sodium alginate (ALG)/polyethyleneimine (PEI) aerogel prepared via a facile chemical crosslinking process as a novel adsorbent with excellent capabilities for removing toxic methyl blue (MB) dye from effluents. Thanks to the synergistic dense oxygen and nitrogen-containing functional groups in the networks, the ALG/SPI/PEI (ASP) aerogel displayed high adsorption capacity for MB (106.3 mg/g) complying the adsorption kinetics and isotherm with the pseudo-second-order and Langmuir models, respectively. Remarkably, the MB adsorption capability of the ASP aerogel surpasses that of its pristine counterpart and outperforms recently reported adsorbents. Moreover, the aerogel maintained >80% of initial adsorption capability in the fourth regenerative cycle, indicating excellent reusability. The superior MB adsorbability coupled with high-efficiency regenerability in this study reveal the significant potential of ASP aerogel in efficiently eliminating organic dye from wastewater.

Compressible polydopamine modified pomelo peel powder/poly(ethyleneimine)/κ-carrageenan aerogel with pH-tunable charge for selective removal of anionic and cationic dyes

In this work, a novel biomass-based aerogel, polydopamine decorated pomelo peel powder/polyethyleneimine/κ-carrageenan (PPEKC) aerogel, was developed for dye wastewater treatment. The as-prepared PPEKC aerogel possessed a robust structure and good compressible resilience. As expected, this aerogel presented remarkable efficacy in eliminating both anionic and cationic dyes. The experimental maximum adsorption capacities were 2016.7 mg g-1 for congo red (CR) at pH = 5 and 1176.6 mg g-1 for methylene blue (MEB) at pH = 11, following with ultra-fast adsorption rates. The adsorption kinetics followed the pseudo-second-order model. The adsorption isotherms exhibited a stronger alignment with the Langmuir isotherm model for CR at 308 K and MEB at 288, 298, 308 K. The Freundlich isotherm model yielded a suitable fit for the adsorption of CR at 288 and 298 K. Thermodynamic analyses indicated that the removal of CR and MEB was spontaneous and endothermic. The adsorption mechanisms involved electrostatic interactions, π-π interactions, and hydrogen bonds. Intriguingly, it could achieve bidirectional selective adsorption of anionic and cationic dyes in the designed pH values, due to pH-tunable surface charge. Additionally, it also exhibited favorable reusability and antibacterial activity. Therefore, the as-prepared PPEKC aerogel could be a promising biosorbent for dye wastewater treatment.

Polyethylenimine Grafted onto Nano-NiFe2O4@SiO2 for the Removal of CrO42-, Ni2+, and Pb2+ Ions from Aqueous Solutions

Polyethyleneimine (PEI) has been reported to have good potential for the adsorption of metal ions. In this work, PEI was covalently bound to NiFe2O4@SiO2 nanoparticles to form the new adsorbent NiFe2O4@SiO2-PEI. The material allowed for magnetic separation and was characterized via powder X-ray diffraction (PXRD), showing the pattern of the NiFe2O4 core and an amorphous shell. Field emission scanning electron microscopy (FE-SEM) showed irregular shaped particles with sizes ranging from 50 to 100 nm, and energy-dispersive X-ray spectroscopy (EDX) showed high C and N contents of 36 and 39%, respectively. This large amount of PEI in the materials was confirmed by thermogravimetry-differential thermal analysis (TGA-DTA), showing a mass loss of about 80%. Fourier-transform IR spectroscopy (FT-IR) showed characteristic resonances of PEI dominating the spectrum. The adsorption of CrO42-, Ni2+, and Pb2+ ions from aqueous solutions was studied at different pH, temperatures, metal ion concentrations, and adsorbent dosages. The maximum adsorption capacities of 149.3, 156.7, and 161.3 mg/g were obtained for CrO42-, Ni2+, and Pb2+, respectively, under optimum conditions using 0.075 g of the adsorbent material at a 250 mg/L ion concentration, pH = 6.5, and room temperature.

Separable calcium sulphate modified biochar gel beads for efficient cadmium removal from wastewater

This study outlines the synthesis of a novel, cost-effective composite material comprising calcium sulphate-modified biochar (Ca-BC) cross-linked with polyethyleneimine (PEI) and sodium alginate (SA), which was subsequently transformed into gel beads (Ca-BC@PEI-SA). These beads were engineered to enable effective cadmium ion (Cd(II)) adsorption from wastewater. Batch adsorption experiments were conducted to evaluate the effects of pH, contact time, temperature, and coexisting ions on adsorption performance. The isotherms and kinetics in the adsorption process were investigated. The results indicated that the removal of Cd(II) by Ca-BC@PEI-SA adheres more closely to the Langmuir model, with maximum adsorption capacities of 138.44 mg/g (15 °C), 151.98 mg/g (25 °C), and 165.56 mg/g (35 °C) at different temperatures. The pseudo-secondary model fit well with Cd(II) adsorption kinetics, suggesting that the removal process was a monolayer process controlled by chemisorption. Moreover, the mechanical strength of the Ca-BC@PEI-SA gel beads allowed easy recovery and reduced secondary contamination. In addition, the adsorption capacity remained nearly constant after four cycles. The main Cd(II) adsorption mechanisms involved surface complexation, ion exchange, and cation-π-bonding interactions.

Efficient adsorption of organic pollutants phthalates and bisphenol A (BPA) utilizing magnetite functionalized covalent organic frameworks (MCOFs): A promising future material for industrial applications

The utilization of phthalates and bisphenol A (BPA) as the major component in plastic and its derivative industry has raised concerns among the public due to the harmful effects caused by these organic pollutants. These pollutants are found to exhibit unique physicochemical properties that allow the pollutants to have prolonged existence in the environment, thus causing damage to the environment. Since phthalates and bisphenol A are used in a variety of industrial applications, the industry must recover these compounds from its water before releasing the pollutants into the environment. As a result, these materials have a promising future in industrial applications. Therefore, the discovery of new quick and reliable abatement technologies is important to ensure that these organic pollutants can be detected and removed from the water sources. This review highlights the use of the adsorption method to remove phthalates and BPA from water sources by employing novel modified adsorbent magnetite functionalized covalent organic frameworks (MCOFs). MCOFs is a new class of porous materials that have demonstrated promising features in a variety of applications due to their adaptable structures, significant surface areas, configurable porosity, and customizable chemistry. The structural attributes, functional design strategies, and specialized for environmental applications before offering some closing thoughts and suggestions for further research were discussed in this paper in addition to developing an innovative solution for the industry to the accessibility for clean water.

Boron-cluster-based porous BCN material modified electrode for electrochemical determination of morphine in serum

Porous highly boron-doped BCN (p-BCN) was produced by using a boron cluster salt (closo-[B₁₂H₁₂]^2-) as the boron-based precursor and SiO₂ as a hard template. The synthesized p-BCN was used in an electrochemical sensor for the ultrasensitive and highly selective detection of morphine (MOP). The optimal conditions for MOP detection were determined by optimizing the experimental conditions. Under these optimal conditions, the p-BCN-based sensor exhibited excellent MOP detection performance (working potential of 0.2 V). Specifically, it showed a detection range of 0.05 to 200 μM and a detection limit of 17.8 nM. Notably, the p-BCN-based electrochemical sensor was successfully applied to the determination of MOP in human blood, and the results showed satisfactory recovery and accuracy. Therefore, this sensor can be used as an effective platform for the detection of MOP in human blood samples.

Facile synthesis of ZIF-8-lignosulfonate microspheres with ultra-high adsorption capacity for Congo red and tetracycline removal from water

Zeolitic imidazolate frameworks (ZIFs) can be used as adsorbent to efficiently adsorb organic pollutants. However, the hydrophobicity of the ZIFs may be easily to form ZIFs nanoparticles aggregates, hampering the effective and practical application in adsorption. In this study, novel spherical composites of ZIF-8 incorporated with lignosulfonate (LS) were synthesized by in-situ growth method. The effects of different mass ratios of LS and Zn in ZIF-8-LS composites were evaluated with respect to structural characteristics and adsorption properties. As an adsorbent for adsorptive removing Congo Red (CR) and tetracycline (TC) from water, the prepared ZIF-8-LS₄ shows the best adsorption capacity of 31.5 mg g^-1 and 48 mg g^-1, respectively. The spherical structure facilitates the contact between the ZIF-8 and the adsorbed substance, in addition to the H-bonding, electrostatic and π-π stacking interactions also contribute to the improvement of the adsorption performance of the ZIF-8-LS₄ composite. The outstanding adsorption capacity and good reusability of the ZIF-8-LS₄ composite provide a good prospect for the effective removal of other contaminants from water.

A novel PEI-grafted N-doping magnetic hydrochar for enhanced scavenging of BPA and Cr(VI) from aqueous phase

Herein, polyethyleneimine (PEI)-grafted nitrogen-doping magnetic hydrochar (PEI_MW@MNHC) was synthesized for hexavalent chromium (Cr(VI)) and bisphenol A (BPA) elimination from water. Characterizations exhibited that abundant amino functional groups, intramolecular heterocyclic N, azo and Fe-N_X structures were successfully introduced into the inherent structure of hydrochar. The obtained PEI_MW@MNHC presented maximum uptake of 205.37 and 180.79 mg/g for Cr(VI) and BPA, respectively, and was highly tolerant to various co-existing ions. Mechanism investigation revealed that the protonated amino, intramolecular heterocyclic N and Fe(II) participated in Cr(VI) reduction, and the N/O-containing groups and Fe(III) fixed Cr(III) onto PEI_MW@MNHC by the formation of complexes and precipitates. On the other hand, azo, Fe-N_X and graphitic N structures contributed to the removal of BPA via pore filling, hydrogen bonding and π-π interactions. Additionally, PEI_MW@MNHC maintained over 85.0% removal efficiency for Cr(VI) and BPA after four cycles, manifesting that PEI_MW@MNHC was an ideal adsorbent with outstanding practical application potential.

Polysaccharide-Based Composite Hydrogels as Sustainable Materials for Removal of Pollutants from Wastewater

Nowadays, pollution has become the main bottleneck towards sustainable technological development due to its detrimental implications in human and ecosystem health. Removal of pollutants from the surrounding environment is a hot research area worldwide; diverse technologies and materials are being continuously developed. To this end, bio-based composite hydrogels as sorbents have received extensive attention in recent years because of advantages such as high adsorptive capacity, controllable mechanical properties, cost effectiveness, and potential for upscaling in continuous flow installations. In this review, we aim to provide an up-to-date analysis of the literature on recent accomplishments in the design of polysaccharide-based composite hydrogels for removal of heavy metal ions, dyes, and oxyanions from wastewater. The correlation between the constituent polysaccharides (chitosan, cellulose, alginate, starch, pectin, pullulan, xanthan, salecan, etc.), engineered composition (presence of other organic and/or inorganic components), and sorption conditions on the removal performance of addressed pollutants will be carefully scrutinized. Particular attention will be paid to the sustainability aspects in the selected studies, particularly to composite selectivity and reusability, as well as to their use in fixed-bed columns and real wastewater applications.

Polyethylenimine-grafted nitrogen-doping magnetic biochar for efficient Cr(VI) decontamination: Insights into synthesis and adsorption mechanisms

Herein, polyethylenimine (PEI)-grafted nitrogen (N)-doping magnetic biochar (PEI_MW@MNBC_BM) was synthesized, and characterization results showed that the microwave-assisted PEI grafting and ball milling-assisted N doping introduced abundant amino, pyridine N and pyrrole N structures onto biochar, which possessed high affinity to Cr(VI) in the anion form. The as-prepared PEI_MW@MNBC_BM displayed pH-dependence adsorption performance and high tolerance to co-existing ions with maximum uptake capacity of Cr(VI) identified as 183.02 mg/g. Furthermore, PEI_MW@MNBC_BM could bind Cr(VI) through electrostatic attraction, complexion, precipitation, reduction and pore filling. Especially, effective reduction of Cr(VI) was ascribed to cooperative electron transfer of partial oxygen-containing functional groups, intramolecular pyridine/pyrrole N, protonated amino and Fe²⁺ on the adsorbent, while oxygen-containing and amino functional groups from N-doping biochar and PEI synergistically complexed Cr(III) via providing lone pair electrons to form coordinate bonds. Furthermore, the stable precipitation was formed between Fe³⁺ and Cr(III). Additionally, the Cr(VI) elimination efficiency could maintain 95.83% even after four adsorption-desorption cycles, suggesting PEI_MW@MNBC_BM as a high-performance adsorbent for Cr(VI) contaminated water remediation.

Synthesis and Characterization of Thermally Stable Lignosulfonamides

Lignin, a highly aromatic macromolecule building plant cells, and cellulose are two of the most commonly occurring natural polymers. Lignosulfonate is a grade of technical lignin, obtained as a by-product in the paper and wood pulping industries, a result of the used lignin isolation method, i.e., sulfite process. In this work, sodium lignosulfonate is used as a starting material to manufacture sulfonamide derivatives of lignin in a two-step modification procedure. Since this direction of the lignin modification is rather rarely investigated and discussed, it makes a good starting point to expand the state of knowledge and explore the properties of lignosulfonamides. Materials obtained after modification underwent characterization by FTIR, SS-NMR, WAXD, SEM, and TGA. Spectroscopic measurements confirmed the incorporation of dihexylamine into the lignin structure and the formation of lignosulfonamide. The crystalline structure of the material was not affected by the modification procedure, as evidenced by the WAXD, with only minute morphological changes of the surface visible on the SEM imaging. The obtained materials were characterized by improved parameters of thermal stability in relation to the raw material. As-prepared sulfonamide lignin derivatives with a potential application as a filler in biopolymeric composites may become a new class of functional, value-added, sustainable additives.