Intraparticle Diffusion Research Articles

Ammonia gas adsorption study using copper impregnated on mesoporous activated carbon from seaweed waste for indoor air purification

Ammonia (NH3), as a toxic gas, has negative impacts on human health even at low concentration, especially in narrowed spaces. In this study, activated carbon was synthesized from seaweed waste and copper was loaded on its surface (Cu/AC filter) to prepare a cost-effective NH3 adsorbent. Pyrolysis (carbonization) temperature can significantly affect the texture properties of activated carbon, and the best activated carbon sample with BET of 1114 m2/g was obtained through pyrolysis at 500 °C followed by KOH-activation at 750 °C. Different from other lignocellulosic biomass-based activated carbons (mainly microporous structure), the prepared algae-based activated carbons mainly have a mesoporous structure (pore size: 7.0–9.0 nm). Copper-impregnation significantly changed the surface chemistry of activated carbon, thereby greatly increasing the NH3 adsorption capacity (max: 128.6 mg/g). The adsorption performance was primarily determined by chemical adsorption (caused by copper impregnation and related inherent functional groups, including O–H, C–H, O–Si–O and SiO–H), followed by physical adsorption (caused by BET). Isotherm studies indicated that NH3 adsorption on Cu/AC filter followed the Langmuir model, whereas the adsorption kinetics followed the pseudo-second-order model. Furthermore, the adsorption mechanism was controlled by intraparticle diffusion model with initial adsorption behavior. This can be attributed to the mesoporous structures of activated carbon, consequently dramatically improving the diffusion efficiency. In addition, the Cu/AC filter showed good regeneration performance, as it can still remain above 90 % after 5 cycles. Finally, this study demonstrated that the seaweed waste is a good precursor for activation carbon and has great potential as excellent NH3 adsorbent for indoor air purification.

Mandarin biochar-CO-TETA was utilized for Acid Red 73 dye adsorption from water, and its isotherm and kinetic studies were investigated

Environmental pollution is a major issue today due to the release of dyestuff waste into the environment through industrial wastewater. There is a need for affordable and effective adsorbents to remove harmful dyes from industrial waste. In this study, Mandarin biochar-CO-TETA (MBCOT) adsorbent was prepared and used to remove Acid Red 73 (AR73) dye from aqueous solutions. The efficiency of dye removal was influenced by various factors such as solution pH, contact time, initial AR73 dye concentration, and MBCOT dosage. All experiments were conducted at 25 ± 2 °C, and the optimal pH was determined to be 1.5. The optimal conditions for dye removal were found to be an AR73 dye concentration of 100 mg/L, an MBCOT dosage of 1.5 g/L, and a contact time of 150 min, resulting in a 98.08% removal rate. Various models such as pseudo-first-order (PFO), pseudo-second-order (PSO), film diffusion (FD), and intraparticle diffusion (IPD) were used to determine the adsorption kinetics of AR73 dye onto MBCOT. The results showed that the PSO model best explains the AR73 dye adsorption. Furthermore, Langmuir and Freundlich's isotherm models were studied to explain the adsorption mechanism using experimental data. The adsorption capacities at equilibrium (qe) in eliminating AR73 dye varied from 92.05 to 32.15, 128.9 to 65.39, 129.25 to 91.69, 123.73 to 111.77, and 130.54 to 125.01 mg/g. The maximum adsorption capacity (Qm) was found to be 140.85 mg/g. In conclusion, this study demonstrates that biochar produced from mandarin peels has the potential to be an effective and promising adsorbent for removing AR73 dye from water.

Analysis of the Sorption Properties of Molecularly Imprinted Polymers as Materials for Potential Monitoring of the Amount of Amoxicillin in an Aqueous Environment

ABSTRACT This work describes a procedure for obtaining molecularly imprinted polymers (MIPs) toward amoxicillin based on methyl methacrylate. To characterize the polymers synthetized, physicochemical and sorption properties were analyzed. The influence of the main parameters on the adsorption efficiency was investigated (the monomers composition of materials, contact time, initial concentration, and regeneration conditions). The adsorption isotherms were fitted by Freundlich, Langmuir, and Dubinin–Radushkevich models. Pseudo-first-order, pseudo-second-order, intraparticle diffusion, and second Fick’s law models were used to fit the kinetic data. Molecularly imprinted polymer which was obtained using 5 wt.% of amoxicillin in relation to the monomers, characterized by the highest sorption value of 4.8 mg/g. This polymer showed selective properties in competition with gentamicin and norfloxacin. Furthermore, in the case of testing imprinted polymers in real samples, materials with an imprint were characterized by higher sorption values compared to those without an imprint (3.27 and 2.02 mg/g, respectively). For the first time, for this type of MIP, we conducted research for regenerating. Water solutions with pH 3 or 9, 1% acetic acid, and ethanol were tested as regeneration solutions. Molecularly imprinted polymer regeneration for the most effective regeneration solution was carried out on SPE columns, allowing a 94% cleaning of the sorption material.

Selenium-Doped Biochar for Removal of Anionic Acid Red and Cationic Crystal Violet Dye

The environmental impact of untreated dye effluent is a concern due to potential mutagenic and allergic effects. This study aims to develop a cost-effective selenium-doped biochar as an adsorbent material to remove acid red (AR) and crystal violet (CV) dyes from water. Selenium nanoparticles (SeNPs) were produced using chemical and biological synthesis methods. The SEM, EDX, XRD, FTIR, and BET surface analysis methods were used to characterize the biochar and selenium-doped biochar (Se-AC and BSe-AC) samples. Surface modification with SeNPs resulted in an increase in surface area to 14.560[Formula: see text]m2/g for Se-AC and 85.456[Formula: see text]m2/g for BSe-AC. Different adsorption isotherms (Langmuir, Freundlich, and Temkin) and adsorption kinetic models (pseudo-firstorder, pseudo-secondorder, and intra-particle diffusion kinetics) were investigated to understand the adsorption patterns of biochar, Se-AC, and BSe-AC. The maximum adsorption capacities of biochar, Se-AC, and BSe-AC for AR and CV dye were found to be between 0.48[Formula: see text]mg[Formula: see text]g[Formula: see text] and 7.51[Formula: see text]mg[Formula: see text]g[Formula: see text], 2.31[Formula: see text]mg[Formula: see text]g[Formula: see text] and 7.86[Formula: see text]mg[Formula: see text]g[Formula: see text], and 6.88[Formula: see text]mg[Formula: see text]g[Formula: see text] and 9.09[Formula: see text]mg[Formula: see text]g[Formula: see text], respectively, at 313[Formula: see text]K. The obtained negative [Formula: see text] indicates effective adsorption, while a positive [Formula: see text] suggests an endothermic reaction for both dyes. BSe-AC is an eco-friendly alternative to biochar for removing AR and CV.

Performance evaluation of calcined eggshell waste (Sorbent) for biogas upgrading: Adsorption isotherms, adsorption kinetics, and fixed bed studies

The use of non-renewable energy resources such as fossil fuels accelerates climate change and environmental degradation necessitating a shift to renewable energy sources. Biogas is a renewable energy resource with great potential. However, its application is limited by the presence of contaminants such as carbon dioxide, which reduces its energy value, and density. Upgrading biogas using locally available materials solves waste management and energy sustainability challenges. In the present study, calcined eggshell waste was employed as an adsorbent for carbon dioxide. The effect of calcination temperature, adsorbent mass and adsorbent particle size was evaluated. The experimental data was fitted to adsorption isotherms, adsorption kinetic models, and breakthrough curves. Eggshells with a particle size of 280 μm, calcined at 850 °C, and mass of 75 g showed the best performance in removing carbon dioxide from biogas. It was noted that data from the experiment fitted Langmuir isotherm with RL 0.00216 while its R2 was 0.97 and Freundlich n = 0.6 while R2 = 0.97. Regarding adsorption kinetics, the intra-particle diffusion model shows good conformity with kid of 34, C of 98, and R2 of 0.977. Breakthrough analysis proved that Yoon Nelson's Model fitted well with the experimental data with an R2 of 0.989. Thus, calcined eggshell waste is a good sorbent for biogas upgrading that can solve the twin challenges of waste disposal and management and energy sustainability.

Application of response surface methodology to optimize chromium (VI) removal from aqueous solution using pre‐treated sawdust

AbstractIncreased chromium usage in industrial applications as chromium III and chromium VI, include metal plating, steel alloys, leather processing, medical applications, and chromium dyeing operations, has resulted in water pollution by Cr (VI) ions, which being toxic and carcinogenic has developed into significant environmental and health problems. The purpose of this research is to remove Cr (VI) ions from synthetic wastewater utilising modified sawdust as an inexpensive adsorbent. Two modified sawdust samples were produced, one using sodium hydroxide and one using sulfuric acid. The experimentation, based on several batch systems, has been undertaken at 25–65°C with 0.5–1.5 g/L sawdust dosage. These conditions were applied to remove Cr (VI) ions at concentrations of 1–6 ppm at pH values from 3 to 10. The results have shown that adsorption onto sawdust followed an intraparticle diffusion mechanism with various rate parameters from 0.65 to 5.24 mg g−1 min, for treated and untreated sawdust. The distribution coefficient , enthalpy , thermodynamic standard free energy , and entropy were determined from a number of temperature studies. Kinetic studies showed that the pseudo‐second order model gave the optimum correlation to the experimental results. The Freundlich and Langmuir isotherms were applied to analyse the experimental equilibrium results. The optimised conditions for the adsorption process were obtained using the D‐optimal design method, and the maximum removal percentage of 100%, was determined at pH = 3, T = 25°C, adsorbent dosage = 1.5 g/L, and an initial Cr (VI) concentration = 5.72 ppm.

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−1 of 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.

Development of a novel MIL‐68‐NH2@MCC composite for enhanced and synergistic removal of methylene blue and Sm(III) from an aqueous environment

In this study, a pioneering composite material, MIL‐68‐NH2@MCC, was synthesized by integrating an indium‐based metal–organic framework (MIL‐68‐NH2) with microcrystalline cellulose (MCC), that could be prepared by recycling different natural products of cellulose. The surface characteristics of the novel MIL‐68‐NH2@MCC composite were meticulously examined through X‐ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy‐dispersive X‐ray spectroscopy (EDX). Remarkably, MIL‐68‐ NH2@MCC demonstrated significantly improved efficiency in removing methylene blue (MB) dye and Sm(III) ions from aqueous solutions, surpassing the removal capabilities of its individual constituents, MIL‐68‐NH2 and MCC. This superior performance can be attributed to the synergistic interplay between MIL‐68‐ NH2 and MCC. We thoroughly investigated the influence of various parameters, including pH, contact time, initial concentration, and temperature. The experimental adsorption data for both MB and Sm(III) exhibited a good fit with the Langmuir isotherm model. The optimized MIL‐68‐NH2@MCC exhibited remarkable maximum adsorption capacities of 133.8 mg/g for MB and 72.1 mg/g for Sm(III). The adsorption kinetics followed a pseudo‐second‐order model with correlation coefficients of 0.9879 and 0.9875 for MB and Sm(III), respectively. The application of intraparticle diffusion and the Boyd kinetic models demonstrated that the film diffusion is the dominant factor influencing the rate of the adsorption process. The study also examined a possible mechanism for the adsorption of MB and Sm(III) on the optimized MIL‐68‐NH2@MCC surface. Ultimately, the results highlight the originality of our research in terms of the efficacy of the newly developed MIL‐68‐NH2@MCC composite as an eco‐friendly adsorbent. Besides, the developed adsorbent effectively removes MB and Sm(III) from different water solutions while exhibiting outstanding selectivity and reusability.

RGO/ZIF-8 Aerogel for Effective Removal of Malachite Green from Wastewater.

In this study, dopamine-modified graphene aerogel (DGA) is synthesized through a one-step hydrothermal method using graphene oxide as the precursor and dopamine as the reducing agent. Subsequently, in situ immersion synthesis is conducted to obtain ZIF-8 loaded on a dopamine-modified graphene aerogel skeleton (ZDGA), featuring a regular honeycomb interconnected mesoporosity and a high specific surface area of 532.8 m2/g. The synthesized ZDGA exhibited exceptional adsorption performance for the cationic dye malachite green. At room temperature, ZDGA achieved an impressive equilibrium adsorption capacity of 6578.34 mg/g. The adsorption process followed pseudo-secondary kinetics and adhered to the Langmuir model, indicating chemically dominated adsorption on a monomolecular layer. Intraparticle diffusion was the primary rate determinant, with π-π stacking, electrostatic adsorption, hydrogen bonding, and Lewis acid-base interactions serving as the key driving forces. It has an ideal specific surface area and good cycling performance, which highlights its potential application in dye wastewater treatment.

The valorization of Prunus mahaleb shell through acid modification for the sorption of Pb2+ removal from aqueous solution

AbstractThis study aimed to investigate the biosorption performance of acid-modified waste Prunus mahaleb (PMA) shells in the removal of Pb2+ ions from aqueous solutions. Changes in the morphological properties and functional components of PMA biosorbent were characterized using SEM–EDX, FT-IR, BET, and PZC analyses. The effect of various parameters such as initial Pb2+ concentration, pH, PMA dosage, contact time, and temperature on biosorption was investigated using a batch biosorption procedure. The maximum biosorption capacity, determined using the Langmuir isotherm, was calculated to be 119 mg g−1. It was found that the biosorption kinetic mechanism followed pseudo-second-order kinetics and intraparticle diffusion model. According to the determined thermodynamic parameters, the biosorption mechanism was found to be endothermic (ΔH° > 0), spontaneous (ΔS° > 0), and entropy-increasing (ΔG° < 0). The outcomes of the experiment were evaluated in comparison to other sorbents that have been previously commonly used in the literature. It was demonstrated that PMA could be a promising, environmentally friendly, cost-effective, and sustainable potential biosorbent for the removal of Pb2+ ions.

Hydroxyapatite-magnetite nanocomposites: Synthesis and superior adsorption properties for lead ion removal, with insights into intraparticle diffusion, kinetic modeling, and phase dependency

Multifunctional superparamagnetic magnetite/hydroxyapatite (Fe3O4/Ca10(PO4)6(OH)2 or MHAp) nano-composites were synthesized via a facile two-step co-precipitation method at room temperature. These magnetic nano-composites underwent heat treatment at various temperatures ranging (400°, 600°, and 900 °C), which were subsequently utilized as nanosorbents for removing Pb2+ ions. The XRD data revealed that both the magnetite and hydroxyapatite synthesized were in a pure phase. In the Fe3O4/HAp composites, there was an augmentation in the intensity peak of hydroxyapatite observed up to 600 °C. However, at 900 °C, a calcium iron phosphate phase emerged, and magnetite (Fe3O4) transitioned into the hematite (Fe2O3) phase. Elevating the heat treatment enhanced the crystallinity of the developed Fe3O4/HAp composites while diminishing the surface area. The prepared nanocomposites exhibited high adsorption efficiency across a wide pH range, with an optimal pH of 5.5. Notably, the adsorption rate of Pb2+ reached 94 % within the first 5 min, with complete metal adsorption progressively at 60 min. The kinetic and isotherm analysis of the adsorption process revealed that pseudo-second-order model and Langmuir model agreed well with the adsorption process. Also, FAH0 demonstrated the highest adsorption capacity (263.2 mg/g) for Pb2+ ions. Furthermore, the Fe3O4/HAp composite NPs exhibited remarkable recyclability even after five cycles of reuse; retaining an efficiency of over 96 %, and allowing for easy separation without a significant loss of adsorption efficiency. The results of the current desorption study underscore the promising practical applications of these nano-composites in decontaminating aqueous media.

Effective and fast removal of ionic dyes from contaminated water using multi‐walled carbon nanotubes decorated with polyelectrolyte brushes

AbstractIn this work, new nanoadsorbents consisting of polymer‐modified multi‐walled carbon nanotubes (MWCNTs) were used to remove toxic ionic dyes, of methylene blue (MB) and methyl orange (MO), effectively from aqueous solutions. The MWCNTs were coated with polymer brushes of poly(potassium 3‐sulfopropyl methacrylate) (PKSPMA) and poly(2‐methacryloyloxyethyltrimethylammonium chloride) (PMETAC) via surface‐initiated atom transfer‐radical polymerization. The PKSPMA@MWCNTs and PMETAC@MWCNTs delivered removal efficiencies of ~80% at pH 7. Maximum adsorption capacity (qmax) reached 411.62 mg/g for MB using PKSPMA@MWCNTs and 224.60 mg/g for MO using PMETAC@MWCNTs, showcasing the effectiveness of these novel nanoadsorbents. The experimental results were analyzed using adsorption isotherm models (Langmuir, Freundlich, and Temkin) and kinetic models (pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion). The Freundlich model provided an excellent fit for MB adsorption on both adsorbents, whereas the Temkin model best described MO adsorption on PKSPMA@MWCNTs and the Langmuir model on PMETAC@MWCNTs. The fitting results showed that the pseudo‐second‐order kinetic model was the most accurate fit for MB and MO adsorption on both nanoadsorbents, suggesting that the removal mechanism was chemisorption. In conclusion, PKSPMA@MWCNTs and PMETAC@MWCNTs demonstrate significant potential as effective adsorbents for dye removal from water, providing a promising approach for water treatment and environmental remediation.

Adsorptive Sequestration of Methylene Blue Dye from Aqueous Solution Using Novel Roystonea regia fruit Pericarp: Isotherm, Kinetics, and Thermodynamics

The batch adsorptive sequestration of methylene blue from an aqueous solution using unripe Roystonea regia fruit pericarp biomass was investigated in this study. The characteristic nature of the biosorbent was studied using various analytical instruments including Fourier Transform Infra-red spectrophotometer, Scanning Electron Microscope, Energy Dispersive X-ray, X-ray diffractometer, and the Brunauer-Emmett Teller. The adsorption study was perfomed at different experimental conditions including pH, contact time, initial dye concentration, temperature, agitation speed, and biosobent dose. From the results of this study, the optimum biosorption of MB was achieved at 120 min contact time, pH 10, room temperature (298 K), 150 rpm agitation speed and dosage of 100 mg/150 mL dye solution. With 132.30 mgg-1 maximum sorption capacity, the Langmuir isotherm best describes the biosorption equilibrium data. At all initial concentrations, the biosorption kinetics of methylene blue onto the biosorbent fitted best to the pseudo-second order kinetics model, with R2 values ≥ 0.999 and qcal being similar to the qexp. The kinetics study also showed the involvement of intra-particle diffusion in the rate-determining step; although not as the sole limiting step of the sorption process. The results of the thermodynamics study showed the high feasibility, spontaneity, and exothermic nature of the biosorption of methylene blue onto the biosorbent. This study concludes that Roystnea regia fruit pericarp would make an economically viable and renewable biosorbent for practical eco-friendly sequestration of MB dye from wastewaters.

Preparation of biomass carbon dots/carboxymethyl cellulose-based fluorescent hydrogel: Combines selective detection and visual adsorption for Copper(II)

Abstract In this study, we used nitrogen-doped carbon dots (NCDs), which were synthesized via the hydrothermal method of corn-stover biomass as raw material and polyethyleneimine (PEI) as the nitrogen source, introduced them into the carboxymethyl cellulose-based hydrogel to prepare an environmentally friendly fluorescent cellulose-based hydrogel (NCDs/CMC-PAM). NCDs/CMC-PAM was also used for simultaneous fluorescence monitoring and removal of Cu (II) in aqueous solution. The chemical and physical structures, adsorption behaviors and fluorescent properties of NCDs/CMC-PAM were investigated. The results showed that NCDs/CMC-PAM exhibited a well-linear response range of fluorescence response for Cu (II) (0∼100 μM, detection limit of 3.42 μM). NCDs/CMC-PAM showed maximum adsorption capacities of 237.71 mg/g for Cu (II), the adsorption process followed the Langmuir isotherm model and pseudo-second-order kinetic model, which is an exothermic spontaneous reaction with an increase in entropy. It can still maintain 79.03% of the original adsorption capacity after six cycles (pH=6). The adsorption mechanisms of NCDs/CMC-PAM for Cu (II) are intraparticle diffusion, electrostatic attraction, ion exchange, and ligand interaction. Hence, the present study provides a new green way to synthesize an adsorbent that can be applied for the adsorption and detection of heavy metal ions.

Peach seed shell and Aspergillus oryzae as adsorbents for the uptake of acid violet 90 dye from wastewater

In this study, Aspergillus oryzae (A. Oryzae) biomass and waste peach seed shells (PPSS) were used to create alternative and effective adsorbents. Acid Violet 90 (AVD) dye was removed from wastewater using the as-prepared adsorbents. Different process variables like pH (2–11), contact period (0–180 min), and adsorbent mass (0.2–2.0 g/L) were examined. The solution pH had a synergistic effect on the improved removal of AVD and the optimal adsorption removal for the PPSS and the A. Oryzae adsorbent occurred at pH 2.0 and pH 5.0, respectively. The findings demonstrated that, in comparison to A. Oryzae, PPSS reported a greater AVD adsorption (mg/g). The equilibrium time for the adsorption process was attained within 180 min for both adsorbents. The adsorption kinetics modelling results showed a good fit with pseudo-second-order kinetics, for both adsorbents, with average R2 values of 0.999 (for PPSS) and 0.997 (for A. Oryzae). Similarly, the isotherm modelling results confirmed the good fitting of the Langmuir isotherm model for A. Oryzae (R2 = 0.999) and the Freundlich model for PPSS (R2 = 0.997). The maximum adsorption capacity (qmax) of 55.0 and 94.92 mg/g was recorded for A. Oryzae and PPSS, respectively. Mechanistic investigation of the present system suggests that both intraparticle diffusion and surface sorption mechanisms control the adsorption rate. As agro materials, both adsorbents are composed of mostly oxygen-based surface functional groups like the –OH, –C = O, -C-O-C, and multiple carbon-carbon bonds, all contributed to the synergistic mechanism interaction between the adsorbent and AVD dye in this study. This study, therefore, revealed that the PPSS and A. Oryzae may be very helpful for removing anionic dye from contaminated wastewater, indicating its potential for useful application in the removal of other major pollutants.

Investigation of effectiveness of KOH-activated olive pomace biochar for efficient direct air capture of CO2

The capture of CO2 directly from the air is one of the most promising methods under investigation in recent years to reduce the environmental concentration of this pollutant in order to mitigate its effects on climate change. In this work, the activation of olive pomace biochar with potassium hydroxide, KOH, has been studied for its use as a CO2 adsorbent. The effectiveness of biochar activated with KOH at 750 °C in an inert N2 atmosphere was evaluated, using different mass ratios of biochar/KOH, 1:0.5, 1:1, and 1:2. Various characterisation analyses of the biochar were performed to determine its chemical composition, specific surface area, pore size and volume, structure, morphology, and functional groups. The adsorption isotherm was determined at atmospheric pressure and a temperature of 10 °C. The experimental equilibrium results were fitted to the Langmuir, Freundlich, and Temkin models. Additionally, the kinetic behavior of biochar/KOH as an adsorbent was studied, and dynamic experiments were conducted at atmospheric pressure and 10 °C. The experimental data were fitted to various kinetic models (pseudo-first order, pseudo-second order, Avrami, and Elovich). Furthermore, the mass transfer mechanism during the adsorption process was evaluated using the intra-particle diffusion model. Finally, biochar regeneration was investigated for its subsequent reuse as an adsorbent. For this purpose, complete desorption of the captured CO2 in the biochar was easily carried out by modifying the temperature.

Desorption and migration of dissolved organics from oil sands tailings to capped water: Demonstration pit lake

Rate and mechanism of organic compounds desorption from fluid fine tailings (FFT) deposits into the capped water are crucial to understand the geochemical stability of end pit lakes. Specifically, the intricate interplay between electrolyte concentrations and seasonal fluctuations along with their impact on the persistence of organic constituents remains insufficiently elucidated. This study utilized PASS-treated FFT (i.e., permanent aquatic structure storage) from Lake Miwasin to address these questions. Experiments were conducted to investigate the desorption of organics from FFT into lake water under different conditions, including FFT dosage, contact time, temperature, and ionic strength. Results revealed that higher FFT dosage and lake water organic matter led to increased desorption of dissolved organic carbon (DOC), while temperature and conductivity of the lake water had minimal effects. The presence of electrolytes regulated the equilibrium desorption capacity of DOC, with cations (K+ and Ca2+) significantly affecting the desorption process from negatively charged treated FFT particles. Temkin isotherms displayed that desorption dynamics followed physically favorable patterns whereas the Intraparticle diffusion kinetic model suggested the equilibrium desorption capacity of DOC as 0.65 mg/g of PASS-treated FFT. A small percentage (5.82 %) of the DOC and less than half of naphthenic acids (NAs) (39.1 %) in PASS-treated FFT were potentially released. The distribution coefficient value of DOC and NAs was comparably high, indicating that DOC and NAs were mostly stable within the PASS-treated FFT deposition. The study reflects considerable stability of PASS-treated FFT about the physical and chemical conditions of the lake water, making them a promising alternative in FFT management.

Design and development of rare earth elements anchored pectin/chitosan integrated magnesia hybrid composite for effective defluoridation of water

Fluoride pollution in drinking water is a worldwide concern arises from natural and human actions. The excessive fluoride present in drinking water leads to fluorosis. In this study, dual polysaccharide biopolymers namely pectin and chitosan were incorporated with magnesia followed by imprinted with lanthanum and cerium ions gives PCML (pectin/chitosan/magnesia/lanthanum) and PCMC (pectin/chitosan/magnesia/cerium) hybrid materials for fluoride adsorption investigation. The enhanced defluoridation capacities (DCs) of PCML and PCMC composites were seen as 4.976 and 4.972 mg g−1 by 30 min individually. To decide the impact of various affecting parameters viz., dosage, initial fluoride concentration, pH, contact time and challenging anions were examined in batch method. The pH results show the utmost DCs of PCML and PCMC composites was noted at pH 6 and in co-ions experiments, the significant competition found with bicarbonate ion owing to the superior electronic building of bicarbonate ion. The defluoridation equilibrium data of PCML and PCMC composites follows Langmuir, pseudo-second-order and intraparticle diffusion models. The positive ΔH° value as 3.04 kJ mol−1 for PCML composite and 2.88 kJ mol−1 for PCMC composite were exposed that the endothermic nature of fluoride adsorption occurs onto PCML and PCMC composites. The defluoridation mechanism of PCML and PCMC composites were attained by complexation, ion-exchange and electrostatic interaction. The reusability results shows that the synthesized PCML and PCMC composites can be reused upto six cycles. Field trail result demonstrates the synthesized PCML and PCMC composites were applicable at field conditions by reducing fluoride concentration below 1.5 mg/L.

Adsorption of arsenic and fluoride: Modeling of single and competitive adsorption systems

The elevated co-occurrence of arsenic and fluoride in surface and groundwater poses risks to human health in many parts of the world. Using single and competitive batch equilibrium adsorption studies, this research focuses on As(V) and F adsorption by activated carbon and its modeling. BET, XRD, FESEM, EDS, and FTIR analysis were used to discern the structural characteristics of activated carbon. The influence of dosage, pH, and contact time were also investigated in single and simultaneous adsorption systems. The maximum adsorption capacity of activated carbon for arsenic and fluoride were found to be 3.58 mg/g and 2.32 mg/g, respectively. Kinetics studies indicated that pseudo-second-order kinetic model fit better than pseudo-first-order, Elovich, and intraparticle diffusion kinetic models. The non-linear regression analysis of Langmuir, Freundlich, Toth, Redlich Petersons, and Modified Langmuir Freundlich models was used to determine single-component asorption model parameters. Additionally, the simultaneous adsorption was rigorously modeled and compared using the Extended Langmuir (EL), Extended Langmuir Freundlich (ELF), Modified Competitive Langmuir (MCL), and Jeppu Amrutha Manipal Multicomponent (JAMM) isotherm models, and competitive mechanisms were interpreted for the simultaneous adsorption system. Further, the model performances were evaluated by statistical error analysis using the normalized average percentage error (NAPE), root mean square errors (RMSE), and the correlation coefficient (R2). According to the modeling results, single equilibrium data fitted better with the Modified Langmuir Freundlich isotherm model, with a higher R2 of 0.99 and lower NAPE values of 3.8 % and 1.28 % for As(V) and F, than other models. For the binary adsorption, the Extended Langmuir Freundlich isotherm model demonstrated excellent fit with lowest errors. All the competitive isotherm models fit the As(V) and F simultaneous sorption systems reasonably well. Furthermore, the research unveiled a nuanced hierarchy of isotherm fitting, with ELF > EL > MCL > JAMM in varying arsenic at a constant fluoride concentration, and ELF > JAMM > EL > MCL in varying fluoride at a constant arsenic concentrations. In addition, competitive studies divulged crucial insights into selective adsorption, as As(V) exhibits a pronounced adsorption selectivity over F on activated carbon. In essence, As(V) showed a more pronounced antagonistic behavior over F, whereas F exhibited a much lesser competitive behavior in the adsorption of arsenic.

Hydrophobic hypercrosslinked polymers prepared by secondary pore-forming method as excellent toluene adsorbents

In this work, inspired by molecular imprinting technology, we developed a secondary pore-forming method to chemically etch three hypercrosslinked polymers which are constructed from three novel hexapolar monomers containing imine groups, resulting in three novel hydrophobic porous hyper-crosslinked polymers (HCPs) pGly-TPA, pP-TPA and pBP-TPA. The structures were determined by FT-IR and solid-state 13C NMR spectroscopic techniques. The specific surface areas of pGly-TPA, pP-TPA and pBP-TPA are 694.1, 197.9 and 497.7 m2/g, respectively. All three porous polymers exhibit high hydrophobic properties with wetting angles of much greater than 90°. The breakthrough adsorption experiments revealed that the three prepared polymers exhibited significant adsorption capacity for toluene (322.05 mg/g for pGly-TPA, 114.43 mg/g for pP-TPA and 279.14 mg/g for pBP-TPA), but showed almost no adsorption for ethyl acetate, cyclohexane, and n-hexane, exhibiting certain molecular size and polarity selectivity. The adsorption behaviors of toluene on pGly-TPA, pP-TPA and pBP-TPA can be fit by the Boltzmann model and the Yoon-Nelson model, suggesting that the fixed bed has low mass transfer resistance. The adsorption rate is controlled by both external diffusion and intraparticle diffusion, as shown by the intraparticle diffusion model analysis. In addition, the adsorption capacity of toluene on pGly-TPA is almost unchanged under high humidity (70 %) or five adsorption–desorption processes, which demonstrates exceptional water-resistance and stability. This work is a reference for preparing novel hydrophobic HCPs using the secondary pore-forming method for removing VOCs from humid air.