Decoration of polylactic acid on graphene oxide for efficient adsorption of methylene blue and tetracycline

Dual-network sodium alginate-chitosan aerogel loaded with UiO-66 for efficient removal of organic pollutants in water: Preparation and mechanism study

Organic pollutants in wastewater pose severe threats to human health and ecosystems. This study used maleic anhydride to adjust chitosan's (CA) surface charge, enhancing solubility and forming a homogenous solution with sodium alginate (SA). Glutaraldehyde cross-linking created a water-stable double network sodium alginate/chitosan composite aerogel (SCCA). UiO-66 was in-situ loaded to produce UiO-66@SCCA, a high-specific-surface-area biopolymer for removing pollutants like ibuprofen (IBP) and methyl orange (MO). UiO-66@SCCA had a surface area of 302.65 m2/g and a UiO-66 loading rate of 48.77 %. Factors affecting adsorption efficiency (time, pH, adsorbent, coexisting ions) were studied. Adsorption followed pseudo-second-order kinetics and Langmuir isotherms, with maximum capacities of 67.39 mg/g for IBP and 45.22 mg/g for MO. Efficiency all remained above 90 % after five cycles. Mechanisms included hydrogen bonding, pore filling, electrostatic interactions, and Electron Donor - Acceptor (EDA) interactions. UiO-66@SCCA shows significant potential for pollutant removal.

Phosphoric acid based geopolymer foam-activated carbon composite for methylene blue adsorption: isotherm, kinetics, thermodynamics, and machine learning studies

In this study, a binary composite adsorbent based on activated carbon and phosphoric acid geopolymer foam (ACP) was prepared by combining phosphoric acid geopolymer (PAGP) with activated carbon (AC) and applied for the removal of methylene blue (MB). Activated carbon was thoroughly mixed with a mixture of fly ash and metakaolin in varying ratios, followed by phosphoric acid activation and thermal curing. The ACP adsorbent was characterized using scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectrophotometer, X-ray diffractometer (XRD), surface area analyser (SAP), and thermogravimetric analyser (TGA). Batch analysis was performed to examine the effects of various adsorption parameters including pH (2, 4, 6, 7, 8, and 10), adsorbent dosage (0.06-0.2 g), MB concentration (50-250 mg L-1), contact duration (up to 240 minutes), and temperature (25-55 °C). The ACP with 70% PAGP and 30% AC was found to be the most suitable adsorbent as it maintained its structure and exhibited better MB adsorption. The ACP had a surface area of 47.36 m2 g-1 and a pore size of 5.6 nm and was found to be amorphous in nature. The adsorption equilibrium reached in 240 minutes at pH 7, indicating an efficient adsorption process. The adsorption increased with the initial dye concentration and decreased with the increase in temperature. The ideal parameters for adsorption of MB using ACP include 0.2 g of adsorbent, 25 °C, pH 10, and 240 minutes. The adsorption data fitted well with the Langmuir isotherm, pseudo-second-order (PSO) kinetics model, and three-step intraparticle diffusion (IPD) model. The adsorption capacity calculated using the Langmuir isotherm was 204.8 mg g-1 with an R 2 = 0.989. Thermodynamics parameters showed that the adsorption process was exothermic, energetically favourable, and associated with a decrease in entropy. According to the FTIR findings, pH effect, Langmuir isotherm, PSO kinetics, IPD model, and thermodynamics factors, chemisorption is identified as the predominant process. Different machine learning models, i.e., gaussian process regression (GPR), support vector regression (SVR and SVR-rbf), random forest regression (RFR), decision tree regression (DTR) and artificial neural network (ANN), were trained and tested using adsorption capacity and % removal data. The ANN model (random search) demonstrated better performance compared to other models, achieving an R 2 value of 0.873 for adsorption capacity and 0.799 for % removal on test data.

Acylhydrazone-functionalized starch for efficient removal of hazardous dyes, heavy metal ion, and sulfides from wastewater: Adsorption behavior and mechanism analysis

Herein, a novel acylhydrazone biosorbent (GSL) with abundant three-dimensional porous structure was successfully prepared by using low-cost starch as raw material for water pollution remediation applications. Various analytical techniques were applied to characterize the morphological structure and chemical composition. Interestingly, the adsorption efficiency of the adsorbent towards Malachite green (MG), Safranin O (SO), Cu2+, and sulfide in the static adsorption experiment was extremely high due to presence of ample functional groups. Additionally, the adsorption isotherm and kinetic experiments revealed that the adsorption processes were based on monolayer chemisorption. The maximum sorption amounts were 2237.4961 mg/g for SO, 2101.6610 mg/g for MG, 410.7019 mg/g for Cu2+, and 483.0194 mg/g for sulfides at 298.15 k. The thermodynamic analysis also demonstrated that all adsorption processes were spontaneous heat processes. The adsorption mechanism was analyzed by FTIR, SEM-EDAX and XPS. The adsorption of SO onto GSL reached 1025.8617 mg/g in continuous adsorption experiments, and the experimental data were fitted through the Thomas model and Yoon-Nelson model. Furthermore, the GSL showed good reusability and salt resistance. Importantly, starch-based acylhydrazone as the adsorbent for the simultaneous removal of hazardous dyes, heavy metal ions and sulfhides has not yet been seen reported.

Removal of Hazardous Organic Dyes from Liquid Wastes Using Advanced Nanomaterials

The presence of organic dyes in aqueous environments is extremely hazardous to life due to the toxicity of these compounds. Thus, its removal from these various aquatic media is of the utmost importance, and several technologies are constantly being tested to meet this goal. Among these technologies, various types of degradation and adsorption techniques are typically used, and of the various types of materials used within these technologies, nanomaterials are constantly being developed and investigated, likely due to the various properties that these nanomaterials have. This work reviewed recent developments (in 2023) about the use of these nanomaterials in the treatment of solutions contaminated with these toxic organic dyes.

Tailoring electrospun nanocomposite fibers of polylactic acid for seamless methylene blue dye adsorption applications

The introduction of biopolymers, which are sustainable and green materials, desegregated nature's water purification proficiency with science and technology, opens a new sustainable methodology in water reclamation. In order to introduce an efficacious adsorbent system for MB dye-toxic pollutant, adsorption, providing robust mechanical properties and facile processability, a facile system was introduced via electrospinning utilizing polylactic acid (PLA) and Ti3C2Tx, viz., PMX. The addition of 3 wt.% Ti3C2Tx led to a 3-fold substantial augmentation in the uptake capacity of the membrane from 197.28 to 307 mg/g when the adsorbate concentration was 100 ppm. The adsorption followed a PSO behavior, proposing that the rate-limiting stage is chemisorption and data best fitted to Freundlich isotherm, indicating heterogeneous adsorption sites and multi-layer adsorption. Further, biodegradability was studied by simulating natural environmental conditions where the nanofibers exhibited 42-64% degradation after 270 days. Based on the result with PLA, it is anticipated that the prepared fibrous system will introduce a new perspective as a potential candidate for MB removal from wastewater, opening new directions toward the research and development in wastewater treatment with electrospun biopolymer fibers using waste PLA.

A floating biosorbent of polylactide and carboxylated cellulose from biomass for effective removal of methylene blue from water

A floating adsorbent bead was prepared from polylactide (PLA) and maleic anhydride (MAH)-modified cellulose in a one-pot process (OP bead). Cellulose was extracted from waste lemongrass leaf (LGL) and modified with MAH in the presence of dimethylacetamide (DMAc). PLA was then added directly into the system to form sorbent beads by a phase separation process that reused unreacted MAH and DMAc as a pore former and a solvent, respectively. The chemical modification converted cellulose macrofibres (55.1 ± 31.5 μm) to microfibers (8.8 ± 1.5 μm) without the need for grinding. The OP beads exhibited more and larger surface pores and greater thermal stability than beads prepared conventionally. The OP beads also removed methylene blue (MB) more effectively, with a maximum adsorption capacity of 86.19 mg⋅g-1. The adsorption of MB on the OP bead fitted the pseudo-second order and the Langmuir isotherm models. The OP bead was reusable over five adsorption cycles, retaining 88 % of MB adsorption. In a mixed solution of MB and methyl orange (MO), the OP bead adsorbed 96 % of the cationic dye MB while repelling the anionic dye MO. The proposed method not only reduced time, energy and chemical consumption, but also enabled the fabrication of a green, effective and easy-to-use biosorbent.

Adsorption behavior and mechanism of modified Pinus massoniana pollen microcarriers for extremely efficient and rapid adsorption of cationic methylene blue dye

Herein, a novel biosorbent was successfully fabricated through a two-step process employing Pinus massoniana pollen as raw material. The efficacy of this biosorbent in eliminating methylene blue (MB), a typical organic cationic dye, from highly concentrated industrial wastewater was investigated. The results demonstrated that by adjusting the wettability of pollen microcarriers, it is possible to significantly increase their adsorption capacity for cationic dyes, resulting in a remarkable 25-fold improvement. The modified Pinus massoniana pollen microcarriers (MPPMC) exhibited an optimal adsorption capacity (585 mg/g) under specific conditions and a rapid equilibrium (97.6% in 5 min, uptake 487.8 mg/g) even at room temperature, showing excellent performance in removing MB efficiently and quickly. It is worth noting that the modified microcarriers could be regenerated via a simple pH-controlled adsorption-desorption cycle, maintaining their superior efficiency (> 99%) even after undergoing five cycles, indicating their excellent reproducibility. The MB adsorption process on MPPMC obeyed the pseudo-second-order kinetic model and followed the Langmuir model. Through the introduced modifications, the substantial deprotonation of carboxyl groups notably augmented electrostatic and hydrogen bonding interactions between MPPMC and MB. Overall, this study offers a sustainable, eco-friendly biological adsorbent, and the MPPMC exhibit the considerable potential for efficient and rapid removal of organic cationic dyes in wastewater.

Adsorption of tetracycline by polycationic straw: Density functional theory calculation for mechanism and machine learning prediction for tetracyclines' remediation

The abuse of antibiotics causes serious environmental pollution, whose removal has become a hot topic. The adsorption of tetracycline (TC) on a prepared polycationic straw (MMS) was investigated. The kinetic, thermodynamic and adsorption isotherm models showed that adsorption of TC by MMS was a spontaneous, monolayer reaction with coexistence of physical and chemical process. Density functional theory indicated that the adsorption of TC resulted from electrostatic interaction and hydrogen bonds, which proved the mechanism of TC by macromolecular biomass for the first time. The expected and empirical values of TC adsorption showed a high fit degree, through predication of machine learning, indicating the feasibility and avoiding lots of experiments. Further, the adsorption ability of MMS to other TCs was predicted, founding that the highest removal efficiency was doxycycline, which provides a novel strategy for removal of other pollution and reduce of economic and time cost in practical application.

Selective adsorption of organic dyes from aqueous environment using fermented maize extract-enhanced graphene oxide-durian shell derived activated carbon composite

A secure aquatic environment is essential for both aquatic and terrestrial life. However, rising populations and the industrial revolution have had a significant impact on the quality of the water environment. Despite the implementation of strong and adapted environmental policies for water treatment worldwide, the issue of organic dyes in wastewater remains challenging. Thus, this study aimed to develop an efficient, cost-effective, and sustainable material to treat methylene blue (MB) in an aqueous environment. In this research, maize extract solution (MES) was utilized as a green cross-linker to induce precipitation, conjugation, and enhance the adsorption performance of graphene oxide (GO) cross-linked with durian shell activated carbon (DSAC), resulting in the formation of a GO@DSAC composite. The composite was investigated for its adsorptive performance toward MB in aqueous media. The physicochemical characterization demonstrated that the cross-linking method significantly influenced the porous structure and surface chemistry of GO@DSAC. BET analysis revealed that the GO@DSAC exhibited dominant mesopores with a surface area of 803.67 m2/g. EDX and XPS measurements confirmed the successful cross-linking of GO with DSAC. The adsorption experiments were well described by the Harkin-Jura model and they followed pseudo-second order kinetics. The maximum adsorption capacity reached 666.67 mg/g at 318 K. Thermodynamic evaluation indicated a spontaneous, feasible, and endothermic in nature. Regenerability and reusability investigations demonstrated that the GO@DSAC composite could be reused for up to 10 desorption-adsorption cycles with a removal efficiency of 81.78%. The selective adsorptive performance of GO@DSAC was examined in a binary system containing Rhodamine B (RhB) and methylene orange (MO). The results showed a separation efficiency (α) of 98.89% for MB/MO and 93.66% for MB/RhB mixtures, underscoring outstanding separation capabilities of the GO@DSAC composite. Overall, the GO@DSAC composite displayed promising potential for the effective removal of cationic dyes from wastewater.