Removal of Acid Violet 17 from Aqueous Solutions by Adsorption onto Activated Carbon Prepared from Pistachio Nut Shell

Adsorption behavior of crude oil hydrocarbons on polyethylene microplastics in batch experiments

This study examines the impact of microplastics on the fate of spilled crude oil in water. Batch adsorption experiments were conducted using polyethylene microplastics ranging in size between 300 and 600 μm. Environmentally relevant concentrations of crude oil and microplastics were tested. Samples processing involved liquid-liquid extraction (LLE) followed by quantitative analysis using Gas-Chromatography coupled to Mass Spectrometry. Kinetic analyses employed the most commonly used models in microplastic adsorption studies, including the pseudo-first order, pseudo second-order, Elovich, and intra-particle diffusion models. Results mainly conformed to the Elovich model, followed by the pseudo-second order model, suggesting chemisorption. Isotherm evaluations involved the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models, selected for their effectiveness in describing the behavior of microplastics in adsorption studies. These models revealed diverse behaviors: alkanes from nC11-nC21 conformed to the Freundlich isotherm, suggesting multilayer adsorption. While nC10, nC27-nC29, nC33, and nC34 were best described by the Langmuir model, and nC22-nC26 and nC30-nC32 adhered to the Temkin model, both indicative of monolayer adsorption. Notably, nC35 adsorption was best described by the Dubinin-Radushkevich model. The different PAHs exhibited preferences for either the Freundlich or the Langmuir model. The maximum adsorption capacities of the contaminants onto polyethylene were 263.12 and 101.57 mg.g-1 for the targeted alkanes and PAHs, respectively, corresponding to a maximum adsorption of 5.75 mg of targeted hydrocarbons per m2 of polyethylene. The study highlighted the potential role of microplastics in influencing the environmental fate of selected crude oil hydrocarbons and provided insights into their interaction and partitioning behavior in water.

Adsorption of Eosin B from Wastewater onto the Prepared Porous Anion Exchange Membrane

This research describes the fabrication of the porous trimethylamine (TMA)-grafted anion exchange membrane (AEM) over a phase inversion process. The synthesis of the generated AEM was verified using Fourier transform infrared (FTIR) spectroscopy. The fabricated porous AEM showed 240% water uptake (WR), 1.45 mg/g ion exchange capacity (IEC), and a 9.0% linear expansion ratio (LER) at 25 °C. It exhibited a porous structure and higher thermal stability. It was utilized to remove eosin B (EB) from wastewater via the process of adsorption. The adsorption capacity of EB increased with time and the starting concentration of EB while decreasing with temperature and the AEM dosage. Adsorption isotherm investigation results showed that EB adsorption onto the porous AEM followed the Langmuir isotherm because the value of correlation coefficient (R2 = 0.992) was close to unity. Because the correlation coefficient was close to one, it was determined through adsorption kinetic experiments that the adsorption of EB on the produced porous AEM was suitable for a pseudo-second-order model. Thermodynamic study about process of EB adsorption on the porous AEM revealed that there was an exothermic (ΔH° = -16.60 kJ/mol) and spontaneous process.

Utilization of shell-based agricultural waste adsorbents for removing dyes: A review

Dye existence in the water body adversely impacts the habitat and the quality of the aquatic system. Considering different physical and chemical methods, adsorption is a propitious substitute for extracting dyes from wastewater specifically due to its performance, high selectivity, less expense, clear operation, and existence in a broad area of experimental circumstances. These benefits are directly linked to the essence of the adsorbent strength used in dye adsorption. In keeping with the principles of green chemistry, the adsorbent materials' accessibility in large amounts that involves easy preparation should boost the effectiveness of the adsorption cycle. Agricultural waste shell-based adsorbent is a novel and better alternative for the expansive adsorbent. This article focuses on the use of a raw and activated adsorbent from agricultural waste shell-based material (on the mitigation of different types of synthetic as well as natural textile dye particles) to find out adsorption capacity based on its operational conditions like pH, dosage, primary concentration of dye, equilibrium time and temperature. Oil palm empty agricultural waste bunch fiber has a maximum adsorption capacity of 393.67 mg/g of Cibacron blue 3G-A dye and Almond shell activated carbon has a maximum adsorption ability of 833.33 mg/g of Methylene Blue dye. Adsorption removal capacity of various raw agricultural wastes and activated agricultural wastes is reviewed. Agricultural waste shell-based adsorbents are a low-cost adsorbent that is a safer alternative to traditional adsorbents.

The adsorption properties of microporous activated carbon prepared from pistachio nut shell for low-concentration VOCs under low-medium temperatures

The control of low-concentration VOCs in coal-fired flue gas is one of the research hotspots at present. In this work, K₂CO₃ and K₂CO₃-KCl were employed to activate the agricultural wastes (pistachio nut shell) to prepare activated carbon (AC), named PSAC-1 and PSAC-2, respectively. By testing the adsorption performance of the prepared AC and commercial activated carbon (CAC) for the five target VOCs, it was observed that the adsorption capacity of PSAC-2 was the best compared to the other two. Particularly, the adsorption capacity of PSAC-2 (225 mg·g^-1) for phenol was 3.8 times that of CAC (59 mg·g^-1). In addition, the pseudo-first-order model, pseudo-second-order model, and Elovich model all fitted the adsorption process well, which indicated that both physical adsorption and chemical adsorption existed simultaneously, in which physical adsorption played a dominant role and chemical adsorption played a minor role. Weber-Morris kinetic model was used to illustrate the rate-controlling mechanism; the results confirmed that the stage of external membrane mass transfer was the control stage of adsorption rate. The results of this study can provide some references for the commercial production of biomass-derived AC and the removal of VOCs in coal-fired flue gas.

Characterization and adsorption applications of composite biochars of clay minerals and biomass

Composite mineral-biochars of a homogeneous biomass (cellulose) and heterogeneous biomass (oak leaves) were fabricated with either 5 wt% or 10 wt% minerals (montmorillonite (MMT), kaolinite, and sand) and then pyrolyzed at 600 °C for 60 min. Characterizations including proximate analysis, ultimate analysis, surface area and porosity, morphology, and surface chemistry confirmed that minerals were present on the surface of biochar, and MMT/kaolinite-biochar composites showed a strengthening in the chars' aromatic structures, as well as increases in oxygen-containing surface functional groups. Methylene blue adsorption isotherms indicated that the MMT/kaolinite-biochars had higher adsorption capacities than pure biomass or biomass-sand biochars (110 mg_MB/g_char and 24 mg_MB/g_char for MMT-cellulose char and cellulose char, respectively). A multilinear model relating adsorption capacity and adsorbent properties was developed to measure the relative contribution of biochar properties to adsorption behavior. The model indicates that pore volume and hydrogen bonding were the dominant properties in controlling the adsorption of methylene blue onto the biochars. Findings from this work indicate that composite biochars prepared from biomass and inexpensive clay minerals are a promising adsorbent for remediating organic contaminants from water.

Nut Shells as Adsorbents of Pollutants: Research and Perspectives

Shells, kernels, and other wastes have been investigated by researchers as potential adsorbents for a number of pollutants like methylene blue (MB), Remazol Rot RB, acid blue 80, acid blue 324, or as raw materials for the production of activated carbons and biochars to serve the same objective. Activated carbons formed by such wastes have been found to remove different heavy metals like uranium, arsenic, and cadmium while their biochars removed others like lead and copper. Furthermore, the production of these adsorbents can be combined with additional ways of valorization of this type of waste like bio-oil or bio-gas generation or even added-value materials extraction. In this work, conducted research on the ability of pistachio, pecan, cashew nut, and castor seed shells to selectively adsorb and thus remove pollutants from synthetic wastewaters is being shown. This type of research needs to be expanded in order to incorporate competitive adsorption, adsorbents regeneration, and recovery of adsorbates and to evaluate their performance with real wastewaters, before they find their way to large scale applications for the removal of the respective compounds from natural waters and wastewaters. An appropriate life cycle assessment is also necessary for the evaluation of the environmental benefits arising from their use.

Biocompatible MIP-202 Zr-MOF tunable sorbent for cost-effective decontamination of anionic and cationic pollutants from waste solutions

This reported work aims to fabricate an eco-friendly Zr bio-based MOF and assessment its adsorption efficiency towards the cationic and anionic dye pollutants including methylene blue (MB) and direct red 81 (DR-81), respectively. Also, its adsorption tendency for the highly toxic heavy metal of hexavalent chromium (Cr(VI)) was compared with dyes. The adsorption performance of bio-MOF showed that the maximum monolayer adsorption capacities were recorded as 79.799 mg/g for MB, 36.071 mg/g for DR-81, and 19.012 mg/g for Cr(VI). Meanwhile, the optimum dosage of as-synthesized MIP-202 bio-MOF was 0.5, 1, and 2 g L^-1 for MB, DR-81, and Cr(VI), respectively. Thermodynamic analysis demonstrated the spontaneous, thermodynamically, and endothermic nature of the decontamination processes onto the fabricated Zr bio-based MOF. The adsorption data were fitted by Langmuir isotherm model compared with Freundlich and Temkin models for all studied water pollutants. Pseudo-second-order kinetic model was a fit model for description of the adsorption kinetics of the different cationic and anionic pollutants onto Zr bio-based MOF. These outcomes indicated that Zr bio-based MOF has potential application for adsorption of different types of industrial water pollutants including cationic and anionic dyes and heavy metals.

Synthesis of DMEA-Grafted Anion Exchange Membrane for Adsorptive Discharge of Methyl Orange from Wastewaters

This manuscript describes the synthesis of dimethylethanolamine (DMEA)-grafted anion exchange membrane (AEM) by incorporating dimethylethanolamine as ion-exchange content into the polymer matrix via the solution casting method. The synthesis of the DMEA-grafted AEM was demonstrated by Fourier transform infrared (FTIR) spectroscopy. The prepared DMEA-grafted AEM exhibited higher thermal stability, homogeneous morphology, water uptake (W_R) of 115%, and an ion exchange capacity (IEC) of 2.70 meq/g. It was used for the adsorptive removal of methyl orange (MO) from an aqueous solution via batch processing. The effect of several operating factors, including contact time, membrane dosage, initial concentration of aqueous dye solution, and temperature on the percentage discharge of MO and adsorption capacity, was evaluated. Experimental data for adsorption of MO onto the DMEA-grafted AEM was analyzed with two parameter and three parameter nonlinear adsorption isotherm models but fitted best using a nonlinear Freundlich isotherm. Adsorption kinetics were studied by using several models, and attained results showed that experimental data fitted well to pseudo-second-order kinetics. A thermodynamic study showed that adsorption of MO onto the prepared DMEA-grafted AEM was an endothermic process. Moreover, it was a feasible and spontaneous process.

Novel eco-friendly electrospun nanomagnetic zinc oxide hybridized PVA/alginate/chitosan nanofibers for enhanced phenol decontamination

In the current study, poly(vinyl alcohol)/alginate/chitosan (PVA/Alg/CS) composite nanofiber was immobilized with six different ratios of nanomagnetic zinc oxide (M-ZnO) (0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1 wt%) via the electrospinning technique. The various fabricated composite (M-6) nanofibers were characterized using Fourier transform infrared (FTIR), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), atomic force microscope (AFM), thermogravimetric analysis (TGA), mechanical testing machine, and optical contact angle measurement. The fabricated composite nanofibers were applied for the adsorption of phenol from aqueous solutions. The 1.0 wt% M-ZnO/PVA/Alg/CS composite nanofibers were selected as the best phenol adsorbent with removal percentage of 84.22%. The influence of different processing parameter such as contact time, composite nanofiber dosage, pH, initial pollutant concentration, and temperature were examined. Increasing nanofiber dosage and the solution temperature was found to enhance the phenol adsorption onto the prepared nanocomposites. The maximum percentage of phenol removal was achieved at 84.22% after 90 min. Meanwhile, the maximum monolayer adsorption capacity (at pH = 5.0) was estimated to be 10.03 mg g^-1 at 25 °C. Kinetic, isotherm, and thermodynamic studies were designated to proof the endothermic, spontaneous, and thermodynamically nature of the phenol adsorption process. These outcomes indicate the effectiveness of the fabricated M-ZnO/PVA/Alg/CS nanofibers as adsorbent materials for phenol from aqueous solutions.

Synthesis of Ag and TiO2 modified polycaprolactone electrospun nanofibers (PCL/TiO2-Ag NFs) as a multifunctional material for SERS, photocatalysis and antibacterial applications

In this study, we reported the design and the fabrication of Ag and TiO₂ modified polycaprolactone (PCL) electrospun nanofiber (NF) mats. The as-prepared NF mats were fabricated by one-step electrospinning and it was exploited for three different purposes (i) reusable SERS substrate for quantitative analysis to trace organic pollutants, (ii) photocatalyst for degradation of organic pollutants and (iii) antibacterial agent for killing of bacteria. Three different nanofiber mats, PCL, PCL-TiO₂, PCL/TiO₂-Ag NFs. were fabricated and further investigated. The morphologies and structures of the as-prepared nanofiber mats were carried out using X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and fourier transform infrared spectroscopy (FT-IR) techniques. PCL/TiO₂-Ag NFs served as a highly effective SERS platform with a detection limit of 10 nM for the detection of methylene blue dye (MB). A remarkable feature of the presented platform is the ability to reuse the PCL/TiO₂-Ag NFs for SERS analysis of MB; availing from its capability for self-cleaning under UV light. By employing PCL/TiO₂-Ag NFs nanocatalyst, complete photocatalytic degradation of the probe analytes MB and ibuprofen (Ibu) under UV irradiation was accomplished not more than 180 min. Moreover, PCL/TiO₂-Ag NF mats showed a highly promising bactericidal feature against gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria, which immensely emerged due to the presence of Ag NPs. This new trending nanofiber is assumed to lead a bunch of changes in the field of photocatalytic, SERS and antibacterial studies.

Synthesis, Characterization, Kinetics, and Thermodynamics of EDTA-Modified Chitosan-Carboxymethyl Cellulose as Cu(II) Ion Adsorbent

A new adsorbent derived from the naturally occurring biopolymers, chitosan (CS) and carboxymethyl cellulose (CMC) was prepared by cross-linking them using EDTA. EDTA having high affinity for metal ions can be used to enhance the chelation properties of the adsorbent enormously. The product obtained (chitosan-EDTA-CMC, CSECM) was characterized by different techniques: FTIR, XRD, SEM/EDAX, TGA, and XPS. The parameters for evaluation of the adsorption properties for removal of Cu(II) ions from the aqueous solution were determined using the batch adsorption method by studying the effect of pH, contact time, initial ion concentration, and temperature on adsorption. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were applied to study the kinetics of the adsorption process, whereas Langmuir, Freundlich, Temkin, and D-R models were applied to evaluate the thermodynamics of the adsorption process. The kinetic adsorption parameters were in best agreement with the pseudo-second-order model, while thermodynamic parameters best fitted to the Langmuir isotherm at different temperatures for adsorption of Cu(II) ions from aqueous solution with a maximum adsorption capacity of 142.95 mg/g at pH 5.5. CSECM showed excellent regeneration capability and recovery of the Cu(II) ion up to five cycles without the loss of the adsorption efficiency, which is the best characteristic to select the appropriate choice of the adsorbent. The adsorbent was also employed in batch experiments to evaluate the adsorption of hardness, producing common metal ions in single and real wastewater solutions.

Removal of Pb(ii) and Cd(ii) from wastewater using arginine cross-linked chitosan-carboxymethyl cellulose beads as green adsorbent

A one pot approach has been explored to synthesize crosslinked beads from chitosan (CS) and carboxymethyl cellulose (CM) using arginine (ag) as a crosslinker. The synthesized beads were characterized by FTIR, SEM, EDX, XRD, TGA and XPS analysis. The results showed that CS and CM were crosslinked successfully and the obtained material (beads) was analyzed for adsorption of Cd(ii) and Pb(ii) by using batch adsorption experiments; parameters such as temperature, contact time, pH and initial ion concentration were studied. Different kinetic and thermodynamic models were used to check the best fit of the adsorption data. The results revealed that the kinetics data of the adsorption of Pb(ii) and Cd(ii) ions shows the best fit with the pseudo second order model whereas the thermodynamics data shows the best fit with the Langmuir isotherm with maximum adsorption capacities of 182.5 mg g-1 and 168.5 mg g-1 for Pb(ii) ions Cd(ii) ions, respectively. For the recovery and the regeneration after the one use of the beads, several adsorption-desorption cycles were carried out to check the reusability and recovery of both the metal ion and the adsorbent without the loss of maximum adsorption efficiency.

Adsorption Kinetics for the Removal of Hazardous Dye Congo Red by Biowaste Materials as Adsorbents

The present work aims to investigate the removal of dye congo red from aqueous solutions by two low-cost biowaste adsorbents such as ground nut shells charcoal (GNC) and eichhornia charcoal (EC) under various experimental conditions. The effect of contact time, ionic strength, temperature, pH, dye concentration, and adsorbent dose on the removal of dye was studied. The kinetic experimental data were fitted to pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich model, and Bangham’s model. Results imply that adsorption of congo red on these adsorbents nicely followed the second order kinetic model and maximum adsorption capacity was found to be 117.6 and 56.8 mg g−1for GNC and EC at 318 K, however it increases with increase in temperature for both adsorbents. Equilibrium isotherms were analyzed by Langmuir, Freundlich, Temkin, Dubinin and Radushkevich, and Generalized Isotherms. Freundlich isotherm described the isotherm data with high-correlation coefficients. The results of the present study substantiate that biowaste material GNC and EC are promising adsorbents for the removal of the dye congo red.