Fabrication of magnetic chitosan-grafted salicylaldehyde/nanoclay for removal of azo dye: BBD optimization, characterization, and mechanistic study

Molecularly imprinted resin modified with ionic liquid for dispersive filter extraction and determination of perfluoroalkyl acids in eggs

Perfluoroalkyl acids (PFAAs) are emerging pollutants that endangers food safety. Developing methods for the selective determination of trace PFAAs in complex samples remains challenging. Herein, an ionic liquid modified porous imprinted phenolic resin-dispersive filter extraction-liquid chromatography-tandem mass spectrometry (IL-PIPR-DFE-LC-MS/MS) method was developed for the determination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in eggs. The new IL-PIPR adsorbent was prepared at room temperature, which avoids the disorder and instability of the template at high temperatures. The imprinting factor of IL-PIPR for PFOA and PFOS exceeded 7.3. DFE, combined with IL-PIPR (15 mg), was used to extract PFOA and PFOS from eggs within 15 min. The established method exhibits low limits of detection (0.01-0.02 ng/g) and high recoveries (84.7%-104.7%), which surpass those of previously reported methods. This work offers a new approach to explore advanced imprinted adsorbents for PFAAs, efficient sample pretreatment technique, and analytical method for pollutants in foods.

Eco-friendly engineering of micro composite-based hydroxyapatite bio crystal and polyaniline for high removal of OG dye from wastewater: Adsorption mechanism and RSM@BBD optimization

The presence of harmful substances such as dyes in water systems poses a direct threat to the quality of people's lives and other organisms living in the ecosystem. Orange G (OG) is considered a hazardous dye. The existing paper attempts to evaluate a low-cost adsorbent for the effective removal of OG dye. The developed adsorbent Polyaniline@Hydroxyapatite extracted from Cilus Gilberti fish Scale (PANI@FHAP) was elaborated through the application of the in situ chemical polymerization method to incorporate PANI on the surface of naturally extracted hydroxyapatite FHAP. The good synthesis of PANI@FHAP was evaluated through multiple techniques including X-ray diffraction (XRD), Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDS), Fourier Transforms Infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) coupled with thermal differential analysis (DTA) analysis. The results reveal a highly ordered disposition of PANI chains on FHAP, resulting in a well-coated FHAP in the PANI matrix. Furthermore, the presence of functional groups on the surface of PANI such as amine (-NH2) and imine (=NH) groups would facilitate the removal of OG dye from contaminated water. The adsorption of OG onto PANI@FHAP was conducted in batch mode and optimized through response surface methodology coupled with box-Behnken design (RSM/BBD) to investigate the effect of time, adsorbent dose, and initial concentration. The outcomes proved that OG adsorption follows a quadratic model (R2 = 0.989). The kinetic study revealed that the adsorption of OG fits the pseudo-second-order model. On the other hand, the isotherm study declared that the Freundlich model is best suited to the description of OG adsorption. For thermodynamic study, the adsorption of OG is spontaneous in nature and exothermic. Furthermore, the regeneration-reusability study indicates that PANI@FHAP could be regenerated and reused up to five successive cycles. Based on the FTIR spectrum of PANI@FHAP after OG adsorption, the mechanism governing OG adsorption is predominantly driven by π-π interaction, electrostatic interaction, and hydrogen bonding interactions. The obtained results suppose that PANI@FHAP adsorbent can be a competitive material in large-scale applications.

Enhancing trimethoprim pollutant removal from wastewater using magnetic metal-organic framework encapsulated with poly (itaconic acid)-grafted crosslinked chitosan composite sponge: Optimization through Box-Behnken design and thermodynamics of adsorption parameters

Trimethoprim (TMP), an antibiotic contaminant, can be effectively removed from water by using the innovative magnetic metal-organic framework (MOF) composite sponge Fe3O4@Rh-MOF@PIC, which is shown in this study. The composite is made up of magnetite (Fe3O4) nanoparticles and a rhodium MOF embedded in a poly(itaconic acid) grafted chitosan matrix. The structure and characteristics of the synthesized material were confirmed by thorough characterization employing SEM, FTIR, XPS, XRD, and BET techniques. Notably, the composite shows a high magnetic saturation of 64 emu g-1, which makes magnetic separation easier, according to vibrating sample magnetometry. Moreover, BET analysis revealed that the Fe3O4@Rh-MOF@PIC sponge had an incredibly high surface area of 1236.48 m2/g. Its outstanding efficacy was confirmed by batch adsorption tests, which produced a maximum adsorption capacity of 391.9 mg/g for the elimination of TMP. Due to its high porosity, magnetic characteristics, and superior trimethoprim uptake, this magnetic MOF composite sponge is a promising adsorbent for effective removal of antibiotics from contaminated water sources. An adsorption energy of 24.5 kJ/mol was found by batch investigations on the Fe3O4@Rh-MOF@PIC composite sponge for trimethoprim (TMP) adsorption. The fact that this value was up 8 kJ/mol suggests that the main mechanism controlling TMP absorption onto the sponge adsorbent is chemisorption. Chemisorption requires creating strong chemical interactions between adsorbate and adsorbent surface groups, unlike weaker physisorption. The magnetic composite sponge exhibited strong removal capabilities and high adsorption capacities for the antibiotic pollutant. The Fe3O4@Rh-MOF@PIC composite sponge also showed magnetism, which allowed for easy magnetic separation after adsorption. Over the course of 6 cycles, it showed outstanding reusability, and XRD confirmed that its composition was stable. The high surface area MOF's pore filling, hydrogen bonding, π-π stacking, and electrostatic interactions were the main trimethoprim adsorption mechanisms. This magnetic composite is feasible and effective for removing antibiotics from water because of its separability, reusability, and synergistic adsorption mechanisms via electrostatics, H-bonding, and π-interactions. The adsorption results were optimized using Box Behnken-design (BBD).

Synergistic adsorption of methylene blue with carrageenan/hydrochar-derived activated carbon hydrogel composites: Insights and optimization strategies

The study explores the use of hydrochar-derived activated carbon (AC) to improve the adsorption capacity and mechanical properties of carrageenan (CAR) hydrogel beads. Four distinct samples, with carrageenan to activated carbon ratios of 1:0 (CAR), 2:1 (CAC2), 4:1 (CAC4), and 10:1 (CAC10), were prepared. These polymeric beads underwent comprehensive evaluation for their methylene blue (MB) adsorption capacity, gel content (GC), and swelling ratio (SR). Increasing activated carbon content up to 50 % of carrageenan mass significantly enhanced GC and SR by 20.57 % and 429.24 %, respectively. Various analytical techniques were employed to characterize the composites, including FTIR, XRD, Raman Spectroscopy, BET, SEM, and EDS-Mapping. Batch adsorption tests investigated the effects of pH, contact time, dye concentration, and temperature on MB adsorption. Maximum adsorption capacities for CAR, CAC10, CAC4, and CAC2 were 475.48, 558.54, 635.93, and 552.35 mg/g, respectively, under optimal conditions. Kinetic models (Elovich and pseudo-second-order) and isotherm models (Temkin for CAR and Freundlich for CAC10, CAC4, and CAC2) fitted well with the experimental data. Thermodynamic analysis showed spontaneous, exothermic MB adsorption. Primary mechanisms include electrostatic attraction, hydrogen bonding, n-π, and π-π stacking. The study highlights enhanced adsorption capacity of carrageenan hydrogel via carrageenan/activated carbon composites, providing cost-effective wastewater treatment.

Development of a novel bionanocomposite of UiO-66/xanthan gum/alginate crosslinked by calcium chloride for azo dye removal: Insight into adsorption kinetics, isotherms, and thermodynamics

In the present work, UiO-66/xanthan gum/alginate bionanocomposite adsorbent was fabricated using the in-situ crosslinking-gelation method, characterized by different techniques, and finally used for the removal of methylene blue dye from aqueous solution. Adsorption studies were performed using batch experiments and the influencing operational parameters such as contact time, initial pH solution, temperature, initial dye concentration, adsorbent dose, pHPZC, swelling, regeneration, and reuse of the adsorbent were investigated. The various kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion) and isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) were used to analysis of the experiment results. The results were best fitted to the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of dye on the adsorbent was obtained at 9.96 mg/g at pH = 11. The value of pHPZC for the adsorbent was obtained at about 8. According to thermodynamic parameters, the dye adsorption was found as spontaneous and endothermic due to the negative value of the ΔG° and ΔH°. After 4 times of reusability cycles, the adsorption efficiency remained above 86 %, which represented a certain regeneration ability. As a result, this research indicates that UiO-66/xanthan gum/alginate bionanocomposite can be utilized as a promising bio-adsorbent for azo dye removal from contaminated wastewater.

Insights into adsorption performance and mechanism of chitosan-bentonite biocomposites for removal of imazethapyr and imazamox

In the present study, chitosan-bentonite biocomposites were synthesised by ultrasonication, characterized using spectral techniques and assessed for their effectiveness in removing imazethapyr and imazamox from aqueous solution. The response surface methodology based box behnken design was utilized to generate optimum conditions viz. pH (1 to 9), adsorbent dose (0.01 to 1.0 g), contact time (0.5 to 48 h) and temperature (15 to 55 °C) for adsorption of herbicides on biocomposites. Based on model predictions, 60.4 to 91.5 % of imazethapyr and 31.7 to 46.4 % of imazamox was efficiently removed under optimal conditions. Adsorption data exhibited a strong fit to pseudo-second-order kinetic (R2 > 0.987) and Freundlich isotherm (R2 > 0.979). The adsorption capacity ranged from 3.88 to 112 μg1-ng-1mLn and order of adsorption was: low molecular weight chitosan-bentonite> medium molecular weight chitosan-bentonite> high molecular weight chitosan-bentonite> bentonite. Thermodynamic experiments suggested a spontaneous, exothermic process, reducing the system randomness during adsorption. Desorption experiments revealed successful desorption ranging from 91.5 to 97.0 % using 0.1 M NaOH. The adsorption mechanism was dominated by synergistic electrostatic interactions and hydrogen bonding. These results collectively indicated the potential environmental remediation application of chitosan-bentonite biocomposites to adsorb imazethapyr and imazamox from wastewaters.

Chitosan-nano CuO composite for removal of mercury (II): Box-Behnken design optimization and adsorption mechanism

The study aimed to develop an adsorbent for extracting mercury (II) from water by combining chitosan beads with green copper oxide nanoparticles. This resulted in the synthesis of the CuO NPs@CSC composite sponge, achieved by loading CuO NPs onto citrate-crosslinked chitosan (CSC). Characterization involved X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The BET method confirmed a higher surface area of the adsorbent at 285.55 m2/g, suggesting its potential for effective mercury (II) removal from water. This research aligns with broader efforts in environmental science and nanotechnology to create advanced materials for water purification. The characterization techniques ensure the suitability of the synthesized material for its intended application, and the significant surface area enhances its capacity for contaminant adsorption. The study investigated the impact of adsorbent dosage, pH, and initial Hg (II) concentration on mercury (II) adsorption. Results showed a fit with the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. Using the Dubinin-Radushkevich model (adsorption energy: 22.74 kJ mol-1), chemisorption was identified. Notably, the adsorption process was found to be endothermic, indicating that higher temperatures led to increased removal capacity and related parameters. This temperature influence was explored systematically. Additionally, the study concluded that the adsorption reaction was spontaneous, evidenced by a positive entropy change. This analysis contributes valuable insights into the thermodynamics and kinetics of mercury (II) adsorption in the studied system. The CuO NPs@CSC composite sponge achieved an impressive adsorption capacity of 672 mg/g. Even after five consecutive cycles, it maintained strong adsorption capabilities with 84.5 % removal efficiency. Remarkably, over six reuse cycles, there were no observable changes in chemical composition, and XRD peaks remained consistent before and after each cycle. The study delved into the interaction mechanism between the CuO NPs@CSC composite sponge and heavy metals. Utilizing the Box-Behnken design (BBD), the adsorption process was optimized for enhanced efficiency.

Facile synthesis of new metal-organic framework/chitosan composite sponge for Hg(II) removal: Characterization, adsorption efficiency, and optimization using Box-Behnken design

The objective of this research was to develop a novel adsorbent to eliminate mercury (Hg(II)) from water. A unique citrate-crosslinked La-MOF/citrate crosslinked chitosan composite sponge (La-MOF@CSC composite sponge) was successfully synthesized in an acidic environment using a one-step technique. Modifying the composition of adsorbent materials is a commonly employed strategy to enhance adsorption capacity, particularly for materials composed of metal-organic frameworks. The study investigated the impact of the composite sponge on the adsorption and removal of Hg(II). The composite sponge exhibited a maximum adsorption capacity (qmax) for Hg(II) at 765.22 mg/g and an impressive high surface area of 1208 m2/g. Various factors influencing the adsorption capacity were taken into account in this study. The adsorption isotherm and kinetics were modeled using Langmuir and pseudo-second-order equations, respectively. Consistent with thermodynamics, the adsorption process was identified as spontaneous and endothermic. The quantities of adsorbed substances increased with rising temperature. The La-MOF@CSC composite sponge demonstrated the ability to be reused up to five times with satisfactory efficiency, retaining its chemical composition and exhibiting similar XRD and XPS data before and after each reuse. The interaction between heavy metals and the La-MOF/CSC composite sponge was examined. Optimization of the adsorption outcomes was conducted using the Box-Behnken design (BBD).

Fabrication of Bacterial Cellulose/Chitosan-MIL-100(Fe) Composite for Adsorptive Removal of Dacarbazine

In this research, a polymeric composite based on a chitosan/bacterial cellulose (CS/BC) matrix filled with MIL-100(Fe) particles was prepared to solve the recyclability of issue MIL-100(Fe) particles and utilized as an efficient adsorbent for removing dacarbazine (DTIC) from wastewater. The adsorption capacity of the composite (CS/BC-MIL) was higher than both MIL-100(Fe) and the CS/BC polymeric matrix. The adsorption performance of the fabricated composite was evaluated through kinetics and isotherm studies. While isotherm studies revealed that the adsorption of DTIC onto the adsorbent can be well described by the Freundlich model, kinetics studies indicated that a combination of factors, rather than a single rate-limiting factor, are responsible for the adsorption rate. Thermodynamics investigation showed that the adsorption of DTIC to CS/BC-MIL composite is exothermic and occurs spontaneously. Additionally, due to the negative entropy change, it was established that the adsorption is governed by the enthalpy change. Exploring the solution chemistry revealed that the optimum pH for the adsorption process was about 4. Moreover, the CS/BC-MIL can selectively adsorb DTIC in the presence of other pharmaceuticals like doxorubicin (DOX). Furthermore, regeneration investigations disclosed that the composite holds its structural features and has an acceptable adsorption capacity after several cycles of adsorption/desorption.

In-situ growth of zinc sulfide on the surface of alginate-based biomass carbon: A new material for removing methylene blue/basic fuchsin and copper ions

This work aims to prepare a composite adsorbent with a fixed shape to improve the performance of carbon materials and to solve the problem of adsorbent in powder form which is difficult to recycle after use. The BC-ZnS composite system was successfully prepared by hydrothermal method based on the preparation of biomass carbon (BC) using alginate (Alg), while the ZnS component was grown in-situ on the surface of BC. The effects of Alg, Zn source, hydrothermal temperature and time on the synthesis of BC-ZnS were explored, the results indicated that ZnS was successfully grown in-situ on the BC surface, while the BC maintained its original morphology. BC-ZnS showed excellent adsorption capacity for methylene blue (MB), basic fuchsin (BF), and copper ions (Cu2+), reaching 301.50 mg/g for MB and exhibiting good cyclic stability. The adsorption of MB/BF/Cu2+ by BC-ZnS was characterized by the presence of multiple forces, where the BC component mainly depended on the electrostatic force of Alg residue, while the ZnS involves electrostatic forces, ion exchange and Lewis acid/base soft-soft interactions. The adsorption process conforms to pseudo-first-kinetics and is a spontaneous entropy-increasing process. BC-ZnS can be a candidate for reusable wastewater treatment and has excellent potential for application.

Removal of aflatoxin B1 from contaminated milk and water by nitrogen/carbon-enriched cobalt ferrite -chitosan nanosphere: RSM optimization, kinetic, and thermodynamic perspectives

In view of the feed/foods inevitably contaminated by toxic and carcinogenic aflatoxin B1 (AFB1), efficient mesoporous metformin-chitosan/silica‑cobalt ferrite nanospheres (Mt-CS/CFS NSs) was prepared to remove AFB1 from aqueous/non-aqueous media. The morphological, functional, and structural characteristics and adsorption properties of C/N-enriched CS/CFS were investigated systematically. The interactive operating variables (temperature (5.0-35 °C); time (10-100 min); AFB1 dose (50-100 μg/mL); and Mt-CS/CFS dosage (0.5-3.5 mg) were optimized via the Box-Behnken design (BBD), which demonstrated good agreement between the experimental data and proposed model. The adsorption efficiency in artificially contaminated cow's milk as well as aqueous environment reached over 91.0 % in a wide pH range (3.0-9.0), without significant change in the nutritional value of milk. Freundlich isotherm and second-order adsorption kinetics were regarded as the most suitable models to fit the adsorption results, and the adsorption rate is dominated by the intra-particle diffusion and boundary layer diffusion. Thermodynamic analyses proved that the process was spontaneous and exothermic. The adsorption mechanism could be explained as physisorption via hydrogen bonding, n-π interaction, and hydrophobic/hydrophilic interactions. The porous Mt-CS/CFS NS derived from chitosan nanoparticles is therefore outstanding adsorbent, offering great adsorptive performance and recycabilities, which impedes economic losses in the food industry.

Chitosan-based magnetic bioadsorbent beads from eucalyptus sawdust waste for the Direct Violet-51 dye remediation: Eco-friendly strategy and statistical optimization

In the present study, a new application was proposed for the eucalyptus sawdust waste, which is an environmental passive. Three adsorbent materials composed of chitosan (CS), sawdust (CSW), and magnetic beads (CSWF) were developed and used for the Direct Violet-51 remediation. The adsorption testes were optimized based on the variation of the adsorption parameters: (i) pH (2-12), (ii) contact time (5-60 min), (iii) initial dye concentration (10-60 mg L-1), (iv) adsorbent mass (10-100 mg) in 10 mL. The optimized conditions of the adsorption essays showed that the three synthesized adsorbents completely removed the dye from the aqueous medium, but under different experimental conditions. As the main findings in this study, we can highlight the excellent performance of CSW adsorbent material, which promoted maximum removal efficiency of Direct Violet-51 at neutral pH, which is of great importance for the industrial processes. On the other hand, CS and CSWF adsorbent materials exhibited a maximum adsorption efficiency at pH 2. Furthermore, the adsorbent materials were applied in the dye remediation in environmental water samples from the tap water, Marcela dam, and Poxim River, they did not suffer any major matrix interference, whose removal efficiency values varied between 99.8 and 100, 70.7-100, and 98.8-99.5 % for the CS, CSW, and CSWF, respectively. Finally, besides being materials produced from the waste, they can be reused more times, fitting into the concept of circular economy.