Maximum Adsorption Research Articles

Conversion of PET bottles into carbonaceous adsorbents for Pb(II) removal from aqueous solutions via KOH activation

In this study, we present a novel approach to repurpose waste Polyethylene terephthalate (PET), a prominent contributor to global plastic usage, for the synthesis of efficient adsorbents via facial pyrolysis. The as-synthesized adsorbents were applied for the removal of lead (Pb(II)) ions in aqueous solution. Controlled batch experiments at pH 5 with 0.075 g of adsorbent at room temperature (20 °C) were conducted to measure Pb(II) adsorption capacities (mg/g) and fitted on isotherm models (Langmuir, Freundlich, and Temkin) and kinetics models (Pseudo-First order, Pseudo-Second order, and Elovich). Thermodynamic experiments conducted at four different temperatures (293 K, 303 K, 313 K, and 323 K) provided enthalpy, entropy, and Gibbs free energy change parameters, explaining the Pb(II) adsorption behaviors on PET-based adsorbents. The activation process involving KOH, followed by carbonization, yielded adsorbents with exceptional surface areas, pore volumes, and elevated oxygen contents (up to 22.8 %). The best adsorbent exhibited superior performance, achieving a maximum adsorption capacity of 219.7 mg/g within a rapid equilibrium time of 15 min. The adsorption behavior adhered well to the Langmuir isotherm model (R2 = 0.999) and Pseudo-Second Order kinetics model (R2 = 0.999). Furthermore, C600K600 displayed outstanding reusability, with negligible efficiency reduction (<5 %) even after five consecutive cycles. These results underscore the successful conversion of PET waste into a low-cost and highly effective adsorbent, offering a promising solution for sustainable waste management.

Preparation of imprinted cryogels of cellulose cross-linked ionic liquids for selective separation of Gd(III) from rare earth leachate

The development of high technology has elevated industry’s dependence on rare earth resources. The hydrometallurgical process is widely used for the separation of rare earth elements (REEs) from rare earth ores, producing acidic leachate with trace amounts of REEs. Recovery of REEs from rare earth leachate not only mitigates the negative impact of leachate on the environment, but also contributes to the realization of sustainable resource utilization. In this study, two novel imprinted cryogel adsorbents, methyltrioctylammonium chloride-derivative carboxymethylated cellulose nanocrystal imprinted cryogel (LR-ICMC) and ethylmethylimidazolium bromide-derivative carboxymethylated cellulose nanocrystal imprinted cryogel (LM-ICMC), were constructed by using carboxymethylated modified cellulose nanocrystals as a backbone structure, and successfully branched ionic liquids (ILs) methyltrioctylammonium chloride-derivative and ethylmethylimidazolium bromide-derivative, respectively, for the separation of gadolinium ions (Gd(III)) from rare earth leachate. Firstly, SEM and TEM results showed that the incorporation of ILs retained part of the pore structure of carboxymethylated cellulose nanocrystals (CMCNCs). BET and TG results illustrated that the incorporation of ILs effectively increased the specific surface area and thermal stability of LR-ICMC and LM-ICMC. FT-IR and XPS results showed that LR-ICMC and LM-ICMC could adsorb Gd(III) by electrostatic and chelating effects. Secondly, adsorption isotherm experiments demonstrated the adsorption capacities of 66.880 mg/g and 75.895 mg/g for LR-ICMC and LM-ICMC, respectively; adsorption kinetic experiments demonstrated the ability of LR-ICMC and LM-ICMC to rapidly adsorb 85.152 % and 87.989 % of the maximum adsorption capacity, respectively, within the initial first 40 min. Finally, cycling experiments demonstrated the advantages of LR-ICMC and LM-ICMC in reuse, maintaining 89.245 % and 90.734 % of the original performance after five adsorption–desorption cycles, respectively. Based on these results, LR-ICMC and LM-ICMC were demonstrated to be highly efficient and reusable adsorbents for selective recovery of Gd(III) from rare earth leachate. This study deepens the application of ILs in solid-phase adsorbents and highlights the great potential of LR-ICMC and LM-ICMC in the field of REEs recovery.

Poly(dimethyldiallylammonium chloride)-modified magnetic bentonite for removal of polystyrene nanoplastics

Nanoplastics (NPs) can contaminate water sources and living organisms, posing significant challenges for removal due to their small size and complex surface properties. There is a need to develop efficient technologies for the removal of NPs. In this study, bentonite was magnetically modified and loaded with Poly(dimethyldiallylammonium chloride) (PDMDAC) to enhance the adsorption for NPs, and improve separation and recovery efficiency. The synthesized PDMDAC-modified magnetic bentonite (PDMMB) had a high specific surface area of 49.386 m2/g and a maximum adsorption capacity of 250.50 mg/g for polystyrene nanoplastics (PS-NPs). The incorporation of PDMDAC increased the surface charge of magnetic bentonite from −39.50 mV to +37.7 mV, generating strong electrostatic attraction to the negatively charged PS-NPs (-64.3 mV). The PDMMB exhibited a saturation magnetization of 17.619 emu/g and an S-type hysteresis curve, indicating strong superparamagnetism that facilitating magnetic separation and recovery. Characterization analysis revealed that the adsorption was driven by electrostatic attraction and the Fe-O functional group. Kinetics and adsorption model analyses indicated that the adsorption mechanism involved electrostatic attraction, complexation, and single/multilayer adsorption, the adsorption process was exothermic and thermodynamically favorable. The adsorption rate remained at 86.41 % after 5 adsorption-desorption cycles. PDMMB exhibited high removal efficiency over a wide range of pH (3−10), ionic strength (0.01–0.5 mol/L), and in the presence of various anion types, indicating its potential for flexible application. The high efficiency, easy operation and excellent regeneration of PDMMB demonstrate its potential for effective removal of NPs from wastewater.

Cadmium sequestration with MgCuAl-layered double hydroxide@montmorillonite nanocomposite in batch and circulated fluidized bed column experiments

In this study, montmorillonite cationic clay coated with MgCuAl-Layered double hydroxide nanoparticles was investigated for its capacity to adsorb cadmium ion (Cd2+) from aqueous solutions. Montmorillonite, MgCuAl−LDH, and a novel MgCuAl-Layered double hydroxide@montmorillonite nanocomposite (MCA−LDH@MMt) were characterized using various mechanisms including BET surface areas, XRD, TEM, FTIR, and SEM/EDS analysis. The adsorption behaviour of MCA−LDH@MMt towards Cd2+ ion was studied using batch and continuous flow systems. pH, contact time, initial Cd2+concentration, MCA−LDH@MMt dose and particle size, agitation speed, and temperature were examined in the batch system. The higher removal efficiency of Cd2+was reported at pH 5 at 70 mg/l initial concentration and 0.2 g/100 ml best adsorbent dose with 150 rpm. The adsorption of Cd2+ on MCA−LDH@MMt followed Langmuir model and yielded a maximum adsorption capacity of 129.82 mg/g. While the pseudo-second-order model better simulates the cadmium kinetics data, and adsorption rate parameters values showing that the adsorption process was chemisorption and the rate-determining step of controlling cadmium adsorption onto MCA−LDH@MMt not intra-particle diffusion. A three-phase, commonly known as gas-liquid-solid circulated fluidized bed column was used to continuously eliminate Cd2+. Four influencing parameters were studied: liquid and air flow rate, bed height, and initial Cd2+concentration. The adsorption efficiency of Cd2+in a continuous system increased when the liquid flow rate decreased and the bed height increased. The time required for MCA−LDH@MMt to reach saturation increases as the bed height and the air flow rate increase. Column data were described using Bohart-Adams, Thomas, and Yoon and Nelson models of adsorption for given experimental conditions. The Bohart-Adams could represent the initial regime of the breakthrough curves, while the Thomas model was better at describing the whole curve of metal ion adsorption for a given experimental condition.

Efficient Adsorption of Methylene Blue Dye Using Ni/Al Layered Double Hydroxide-Graphene Oxide Composite

To address environmental pollution, we developed Ni/Al layered double hydroxide-graphene oxide (Ni/Al-GO) adsorbent materials for the purpose of eliminating methylene blue (MB) dye pollutants. The adsorption process was explored by examining many experimental factors, including temperature, regeneration/reuse procedure, pH, and time, and their effects on the material. The appropriate model for the isotherm is the Langmuir isotherm. The Ni/Al-GO material achieved a maximum adsorption capacity of 61.35 mg/g for MB dye at a temperature of 60 °C. The thermodynamic characteristics indicate that the adsorption process is both endothermic and spontaneous as the temperature increases. The regeneration method demonstrated that the Ni/Al-GO material has a highly stable structure, enabling it to be utilized for five cycles with a remarkable regeneration rate of 93.49% in the fifth cycle. The pH that yielded the best results for all materials was pH 10, and the kinetic model demonstrated a pseudo second-order behavior. Copyright © 2024 by Authors, Published by MKICS and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Deep learning artificial neural network framework to optimize the adsorption capacity of 3-nitrophenol using carbonaceous material obtained from biomass waste

The presence of toxic chemicals in water, including heavy metals like mercury and lead, organic pollutants such as pesticides, and industrial chemicals from runoff and discharges, poses critical public health and environmental risks leading to severe health issues and ecosystem damage; education plays a crucial role in mitigating these effects by enhancing awareness, promoting sustainable practices, and integrating environmental science into curricula to empower individuals to address and advocate for effective solutions to water pollution. However, the educational transformation should be accompanied with a technical process which can be eventually transferred to society to empower environmental education. In this study, carbonaceous material derived from Haematoxylum campechianum (CM-HC) was utilized for removing 3-nitrophenol (3-Nph) from aqueous solutions. The novelty of this research utilizes Haematoxylum campechianum bark and coconut shell, abundant agricultural wastes in Campeche, Mexico, for toxin removal, enhancing the adsorption process through artificial neural networks and genetic algorithms to optimize conditions and maximize the absorption efficiency. CM-HC’s surface morphology was analyzed using scanning electron microscopy (SEM/EDS), BET method, X-ray powder diffraction (XRD), and pHpzc. Kinetic models including pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich were applied to fit the data. Adsorption isotherms were determined at varying pH (3–8), adsorbent dosages (2–10 g/L), and temperatures (300.15–330.15 K), employing Langmuir, Freundlich, Temkin, and Redlich–Peterson models. PSO kinetics demonstrated a good fit (R2 > 0.98) for Ci = 50–100 mg/L, indicating a chemical adsorption mechanism. The Langmuir isotherm model exhibited the best fit, confirming chemical adsorption, with a maximum adsorption capacity (Qm) of 236.156 mg/g at T = 300.15 K, pH = 6, contact time = 3 h, and 2 g/L adsorbent dosage. Lower temperatures favored exothermic adsorption. Artificial neural networks (ANNs) were employed for deep learning, optimizing the predictive model for removal percentage. Correlation heat maps highlighted positive correlations between time, dosage, and removal percentage, emphasizing the impact of initial concentration on efficiency. ANN modeling, incorporating iterative optimization, yielded highly accurate predictions, aligned closely with experimental results. The study showcases the success of deep learning in optimizing adsorption processes, emphasizing the importance of diverse correlation algorithms for comprehensive insights into competitive adsorption dynamics. The 5-14-14-1 deep learning architecture, fine-tuned over 228 epochs, demonstrated strong performance with mean squared error (MSE) values of 4.07, 18.406, and 6.2122 for training, testing, and total datasets, respectively, and high R-squared values. Graphical analysis showed a solid linear correlation between experimental and simulated removal percentages, emphasizing the need to consider more than just testing data for optimization. Experimental validation confirmed a 98.77% removal efficiency, illustrating the effectiveness of combining deep learning with genetic algorithms, and highlighting the necessity of experimental trials to verify computational predictions. It is concluded that the carbonaceous material from Haematoxylum campechianum waste (CM-HC) is an effective, low-cost adsorbent for removing 3-nitrophenol from aqueous solutions, achieving optimal removal at pH 6 and 300.15 K with a maximum adsorption capacity of 236.156 mg/g, following Langmuir model and pseudo-second order kinetics. The validated ANN model offers a reliable tool for practical applications in environmental remediation, advancing both environmental science and educational innovation by integrating artificial neural networks and data science methodologies into student learning experiences.

Enhanced adsorption of tylosin by ordered multistage porous carbon and efficient in-situ regeneration of saturated adsorbents by activated persulfate oxidation: Performance, mechanism and multiple cycles

In this study, a novel ordered multistage porous carbon (OMPC) with a micro-mesoporous structure was prepared and used for the removal of tylosin (TYL). The porous material, carbonized at 900 °C (OMPC-900), exhibited micro-mesoporous structures with pore sizes of 0.71 nm and 3.63 nm, while had a specific surface area of 1300.02 m2 g−1. OMPC-900 demonstrated a maximum adsorption capacity of 341.28 mg g−1 for TYL in water by electrostatic attraction, hydrogen bonding, π-π interactions, and pore-filling mechanisms, which is 6.41 times higher than that of activated carbon. The TYL-saturated adsorbents could be efficiently regenerated by in-situ oxidation through the activation of persulfate (PDS), achieving a regeneration rate of 94.17%, significantly higher than that of activated carbon (55.22%). The excellent regeneration performance may be attributed to the presence of -C=O and graphitic carbon in the adsorbent, which promotes the production of free radicals (•OH, SO4•- and •O2−) and non-free radicals. Among these, the non-radical pathways (1O2 and electron transfer) played a key role in the degradation of TYL loaded on the adsorbent. OMPC-900 maintained stable regenerative adsorption performance of 80.85% after five in-situ regeneration, and the normalized adsorption capacity per unit surface area increased from 0.21 to 0.39 mg m−2, which may be due to that the increase in oxygen-carbon ratio and surface defects improved the adsorption sites activity of the regenerated adsorbent. In comparison to conventional pyrolysis and organic solvent elution, oxidative regeneration through the activation of PDS is a more efficient and sustainable method.

Synthesis and characterization of amine functionalized silylated clay for heavy metal adsorption: Thermodynamic and kinetic studies on Fe(III) ion

Amine functionalized bentonites were used as adsorbents for the bioremoval of Fe(III) ions, which led to the inclusion of functional groups such as -OH, -NH2, -OCH3, etc. FTIR, XRD, SEM, AFM, TG, BET, XRF, and CHNS analyzer were used to analyze the surface and textural characteristics. The influence of adsorption factors, such as pH, contact time, temperature, and initial concentration, have been investigated and tailored in batch adsorption experiments of Fe (III) metal ions. The maximum adsorption efficiency and capacity of modified BNT-APTMS is 100.90 % and 103.91 mg/g respectively. The adsorption process is best fit with Freundlich model (R2=0.998) than Langmuir model (R2=0.788) and the Temkin model D-R isotherm parameters indicating a physisorption process. A mechanism of spontaneous complexation was accomplished, because of the heterogeneity of the surface, electrostatic forces, pore filling, and π-π stacking. Follows PSO kinetics and favours Freundlich isotherm. The adsorbent substance showed a remarkable capacity for regeneration, assuring the substance's stability and reusability.

Evaluation of Na2CO3-doped MCM-48-Li4SiO4 adsorbent for CO2 capture: Performance and DFT mechanism

Efficient CO2 adsorbents are crucial for addressing the global climate crisis. In this study the novel adsorbents were synthesized using an impregnation precipitation method with MCM-48 as the silica source and Li2CO3 as the lithium source. By doping alkali metal carbonate (Na2CO3), the ML-Na2CO3 adsorbent was created for high-temperature CO2 capture. The results showed that the maximum adsorption capacity of 35.63 wt% was achieved at 600℃ in the mixture (15 vol% CO2, the balance being N2)when the adsorbent contained 15 wt% Na2CO3, representing a 4.49 wt% increase compared to the undoped ML adsorbent. The adsorption kinetics analysis confirmed a good fit with the biexponential model. Density Functional Theory (DFT) simulations revealed that the adsorption energy increased by an average of 0.1035 eV and Oslab exhibited high activity in chemisorbing CO2, forming CO32−. Na2CO3 doping modified the electronic structure of Oslab and Lislab, resulting in increased high-energy electrons, reflective activity, and improved CO2 adsorption energy. Overall, incorporating Na2CO3 enhanced carbon dioxide adsorption performance by 114.42 %, indicating a promising potential for real flue gas CO2 adsorption applications.

Citrus limon peel-based biosynthesis: Lead oxide, zinc oxide, cadmium oxide, and copper oxide nano quantum dots for subtraction of anionic Actas Pink dye (AAPD)

ABSTRACT Adsorption is a highly effective method for wastewater quality adjustment, offering advantages such as low cost and availability of adsorbents. This study investigates the efficient removal of Anionic Actas Pink dye (AAPD), a major contributor to environmental pollution. Green adsorbents including lead oxide (PbO), zinc oxide (ZnO), cadmium oxide (CdO), and copper oxide (CuO) were synthesized via eco-friendly routes for AAPD removal. Maximum adsorption capacities (qe) were observed at pH 7 (PbO, ZnO, CdO) and pH 2 (CuO and native) with values of 83.83 mg/g at 100 ppm, 75.65 mg/g at 100 ppm, 70.50 mg/g 75 ppm, 61.21 mg/g at 150 ppm, and 52.69 mg/g at 150 ppm, respectively, using an adsorbent dose of 0.05 g/50 mL at temperature of 37°C, and 90 min contact time. Adsorption followed Langmuir isotherm for all adsorbents except native, with PbO also fitting Freundlich and Dubinin–Radushkevich isotherms. Kinetics adsorption data supported pseudo-second-order, while thermodynamic analysis indicated spontaneous and exothermic nature. Effects of electrolytes, surfactants, and desorption were also evaluated. Characterization through FTIR, SEM, and XRD confirmed the morphology and functional groups of these nano-quantum dots. Citrus limon peel-based biosynthesis offers sustainable, eco-friendly, and cost-effective alternatives, highlighting their potential for dye adsorption.

The resistance mechanism of humic acids and proteins in soluble microbial products from activated sludge against silver nanoparticles

In the process of activated sludge against silver nanoparticles (AgNPs) present in wastewater, soluble microbial products (SMP) produced by microbial secretion or macromolecular cell lysis formed a reactive barrier against AgNPs. Proteins (PN) and humic acids (HA), the primary constituents of SMP, were extracted from activated sludge in this study. The adsorption mechanism of HA, which had excellent adsorption properties, on AgNPs was first analyzed. Then, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were further used to explore the bonding mechanisms of AgNPs by HA and PN, respectively. The results showed that the surface structure of HA was cracked after resisting AgNPs, and the adsorption process on AgNPs was monomolecular layer adsorption, with the maximum adsorption capacity of 12.9 mg/g at 35 °C. Thus, HA was an adsorbent with medium adsorption capacity. The FTIR and XPS analyses demonstrated that HA chelated and chemisorbed with AgNPs through chemical bonds such as -OH, C-H, CC, C-N, CO, and C-O-C, thereby reducing the microbial cytotoxicity of AgNPs. The chemical reaction between PN and AgNPs occurred via -OH and C-H dependent hydrogen bonding, and N-H was oxidized to -NO3, which ultimately resulted in the destruction of the PN peptide chain structure and the change of PN conformation. The present study investigated the resistance mechanism of HA and PN, the main components of SMP in activated sludge system, under the stress of AgNPs, which can provide theoretical support for the in-situ bioremediation of AgNPs in wastewater and the potential application of SMP.

Organo magadiites for diclofenac adsorption: influence of the surfactant chain.

The presence of drugs in aquatic environments has been considered a global challenge and several remediation technologies have been proposed, including adsorption. In this study, new diclofenac adsorbents were obtained from the reaction of sodium magadiite (Na-Mag) with surfactants dodecylpyridinium chloride hydrate (C12pyCl) and hexadecylpyridinium chloride monohydrate (C16pyCl)), 1-hexadecyltrimethylammonium bromide (C16Br), and dodecyltrimethylammonium bromide (C12Br). The synthesis was carried out in the microwave at 50°C for 5min using surfactant amounts of 100% and 200% in relation to the cation exchange capacity of Na-Mag. The elemental analysis indicated that surfactants with a longer organic chain were more incorporated into Na-Mag, whose values were 1.42 and 1.32mmolg-1 for C16pyMag200% and C16Mag200%, respectively. X-ray diffraction results suggested formation of intercalated products with basal space in the range of 2.81-4.00nm. Diclofenac was quickly adsorbed on all organophilic magadiites, at an equilibrium time of 1min. Drug capacity adsorption was influenced by the arrangement and packing density of organic cations, the basal distance, and the organic contents of the samples at high drug concentrations. Alkylpyridinium magadiites exhibited maximum adsorption capacities higher than alkylammonium magadiites, of 96.4, 100.7, 131.7, and 166.1mgg-1 for C12pyMag100%, C12pyMag200%, C16pyMag100%, and C16pyMag200%, respectively, at pH 6.0 and 30°C. Diclofenac removal by samples was not affected by the presence of ibuprofen, which was also removed from binary system by organophilic magadiites reaching removal of 76.5% and 86.9% by C16pyMag100% and C16pyMag200%, respectively. Regeneration studies demonstrated a drug removal percentage of 83-92% for C16pyMag and C16Mag after three cycles of adsorption.

Production of Low-Cost Adsorbents within a Circular Economy Approach: Use of Spruce Sawdust Pretreated with Desalination Brine to Adsorb Methylene Blue.

A sustainable low-cost activated carbon substitute was produced based on pretreated lignocellulosic biomass, especially spruce sawdust. A harmful liquid waste, desalination brine, was used for the treatment of a solid wood industry waste, spruce sawdust. This approach is in the circular economy theory and aims at the decarbonization of the economy. Pretreated sawdust was tested as an adsorbent appropriate for the removal of a commonly used pollutant, methylene blue, from industrial wastewater. The adsorption capacity of the pretreated material was found to have increased four times compared to the untreated one in the case that the Freundlich equation was fitted to the isotherms' data, i.e., the one with the best fit to the isotherm's experimental data of the three isotherm models used herein. The treatment experimental conditions with desalination brine that gave maximum adsorption capacity correspond to a 1.97 combined severity factor in logarithmic form value. Moreover, a kinetic experiment was carried out with regard to the methylene blue adsorption process. The desalination brine-pretreated sawdust adsorption capacity increased approximately two times compared to the untreated one, in the case when the second-order kinetic equation was used, which had the best fit of the kinetic data of the three kinetic models used herein. In this case, the pretreatment experimental conditions that gave maximum adsorption capacity correspond to -1.049 combined severity factor in logarithmic form. Industrial scale applications can be based on the kinetic data findings, i.e., spruce sawdust optimal pretreatment conditions at 200 °C, for 25 min, with brine solution containing 98.12 g L-1 NaCl, as they are related to a much shorter adsorption period compared to the isotherm data.

Amino-functionalized magnetic humic acid nanoparticles for enhanced Pb(II) adsorption: Mechanism analysis and machine learning prediction

It is an effective removal method to adsorb heavy metals by adsorption materials, so as to realize their separation from environmental media. Optimizing the structure of the materials and adsorption conditions are essential for improving the adsorption performance. Amino-functionalized magnetic humic acid nanoparticles (AF-MHA) was synthesized using a co-precipitation method. And the adsorbing material showed remarkable lead (Pb(II)) adsorption capacity under neutral pH conditions and a maximum adsorption capacity of 119 mg/g. The adsorption process was attributed to complexation with functional groups like amine, carboxyl, and phenol hydroxyl. In order to enhance the optimization of adsorption parameters, machine learning (ML) models including Artificial Neural Network (ANN), Random Forest (RF), Support Vector Regression (SVR), and CatBoost were employed. After comparative study we find the CatBoost model was found to be the most accurate predictor with a correlation coefficient of R2=0.95. ML also facilitated the identification of key factors influencing adsorption capability by assessing the importance of input features. With ML-assisted optimization parameters offering a strategic advantage in optimizing adsorption conditions and enhancing performance, AF-MHA is a promising adsorbent for treating divalent metal-contaminated water.

Post-synthetic modification of zirconium-based metal-organic frameworks for enhanced simultaneous adsorption of heavy metal ions and organic dyes

Heavy metal and dye pollution pose a serious threat to human health and ecology, and there is an urgent need to develop novel adsorbent materials for wastewater treatment. In this study, a novel functionalized zirconium-based MOF UiO-66-Gd was prepared by a post-synthetic modification strategy and used for the simultaneous removal of Pb2+, Cu2+ and methylene blue (MB) from wastewater. UiO-66-Gd retained the crystalline structure and morphological features before modification. The specific surface area reached 574.94 m2/g, which can provide abundant active sites for adsorption. The effects of several factors on the adsorptive performance of UiO-66-Gd were investigated by batch adsorption experiments. The adsorption of Pb2+ by UiO-66-Gd reached the adsorption equilibrium in only 5 min. The theoretical maximum adsorption capacities for Pb2+, Cu2+ and MB were 833.33, 354.61 and 564.91 mg/g, respectively. In addition, UiO-66-Gd has excellent anti-interference and regeneration properties with potential for practical applications. Competition adsorption experiments showed that UiO-66-Gd had the greatest affinity for Pb2+. The adsorption of UiO-66-Gd on Pb2+ and Cu2+ was mainly through electrostatic interactions and chelation, and on MB mainly through electrostatic interactions, π-π interactions and hydrogen bonding. Overall, UiO-66-Gd has great potential for application in the removal of Pb2+, Cu2+ and MB.

Removal of antibiotics from aqueous solutions: insights of competitive adsorption onto Ni-impregnated biochar of spent coffee grounds

Antibiotics are among the most widely used pharmaceutically active compounds. Possessing the capability to adversely impact the ecological system, existence of antibiotics in the environment is an escalating concern. With the purpose of removing two widely used antibiotics efficiently from aqueous solutions, the competency of two biochar (BC)-based sorbents derived from spent coffee (SC) grounds was investigated. Both pristine (SCBC) and nickel (II) oxide-impregnated (Ni-SCBC) biochars were utilized as sustainable and cost-effective sorbents to remove daunorubicin (DAYN) and tigecycline (TIGY) from single synthetic aqueous solutions and binary combinations. Batch adsorption experiments were controlled implementing Box–Behnken design. The removal efficiency of Ni-SCBC was superior compared to SCBC (TIGY: 67.06%, DAYN: 94.30%). Results of characterizations showed that impregnation with NiO changed the degree of crystallization with a remarkable increase in the surface area from 49.23 m2/g in SCBC to 86.06 m2/g in Ni-SCBC. Adsorption of DAYN and TIGY (single solutions) conformed well to Freundlich, and Langmuir isotherms, respectively. A maximum adsorption capacity (qmax) of 136.62 mg/g (DAYN) and 73.15 mg/g (TIGY) was reported in single solutions, compared to 23.50 mg/g (DAYN) and 58.42 mg/g (TIGY) in binary mixture. Adsorption kinetics onto Ni-SCBC fitted well with the pseudo-second-order (PSO) and Elovich models. Acquired results demonstrated that SCBC and Ni-SCBC are promising adsorbents for remedying antibiotics.

A two-dimensional cobalt-based metal–organic framework efficiently adsorbs Cr(VI) from wastewater

Metal-organic frameworks (MOFs) display multi-level pores and abundant adsorption sites, which can effectively adsorb Cr(VI) from wastewater. In this paper, x-ray single crystal diffraction analysis showed that both the N atom and two carboxyl groups in L2− of [Co(L)(H2O)2]n (1) (H2L = 3, 5-pyridinedicarboxylic acid) underwent coordination reactions with Co(II) in μ3-η1:η1:η1 fashion, giving rise to the formation of a two-dimensional structure. The nano adsorbent of 1 (2D-Co-MOF-N) with a particle diameter about 100 nm was successfully prepared by cell disruption method. The optimal conditions for 2D-Co-MOF-N to adsorb Cr(VI) from wastewater were observed at pH 6.5, T = 30 °C, and a dosage of 0.10 g/L, achieving a maximum adsorption capacity of 207.93 mg/g which was better than most MOFs adsorbents. The present of Cl−, NO3–, SO42−, and PO43− in wastewater inhibited the adsorption of Cr(VI) by 2D-Co-MOF-N due to competitive adsorption. Cycling experiments showed that 2D-Co-MOF-N exhibited admirable structural and performance stability, which could be deemed as a potential candidate for the removal toxic ions from actual wastewater.

Activated Iron-Porous Carbon Nanomaterials as Adsorbents for Methylene Blue and Congo Red.

The adsorption properties of microporous carbon materials modified with iron citrate were investigated. The carbon materials were produced based on resorcinol-formaldehyde resin, treated in a microwave assisted solvothermal reactor, and next carbonized in the tube furnace at a temperature of 700 °C under argon atmosphere. Iron citrate was applied as a modifier, added to the material precursor before the synthesis in the reactor, in the quantity enabling to obtain the nanocomposites with C:Fe mass ratio equal to 10:1. Some samples were additionally activated using potassium oxalate or potassium hydroxide. The phase composition of the produced nanocomposites was determined using the X-ray diffraction method. Scanning and transmission electron microscopy was applied to characterize the changes in samples' morphology resulting from the activation process and/or the introduction of iron into the carbon matrix. The adsorption of nitrogen from gas phase and dyes (methylene blue and congo red) from water solution on the obtained materials was investigated. In the case of methylene blue, the adsorption equilibrium isotherms followed the Langmuir isotherm model. However, in the case of congo red, a linear dependency of adsorption and concentration in a broad equilibrium concentration range was found and well-described using the Henry equation. The most efficient adsorption of methylene blue was noticed for the sample activated with potassium hydroxide and modified with iron citrate, and a maximum adsorption capacity of 696 mg/g was achieved. The highest congo red adsorption was noticed for the non-activated sample modified with iron citrate, and the partition coefficient for this material equaled 171 dm3/g.

Engineering the cell wall reactive groups of Plant Growth Promoting Rhizobacteria by culture strategy for heavy metal removal

This research delved into the effects of nutrient limitation on the level of sporulation and the cadmium adsorption capacity of the bacterium Bacillus sp. isolated from the rhizosphere of endemic soils in the Region of Valparaiso, Chile. The bacteria were subjected to nitrogen limitation in fed-batch mode and were compared to bacteria grown in batch culture without nutrient limitation. The cultures were carried out in a 3 L bioreactor with an external nitrogen supply of ammonium at a flow of 0.123 L h−1. The specific maximum growth rate was 0.42 h−1 in batch and 0.45 h−1 in the exponential phase of the fed-batch.The analysis of sporulation did not show any significant difference between the biomass coming from the fed-batch and batch cultures.It was found that maximum cadmium adsorption capacity varied with culture strategy. The dry biomass grown without nutrient limitation exhibited a maximum adsorption capacity for cadmium of 65.0 mgCd g−1biomass. Conversely, the limited biomass achieved a lower cadmium adsorption capacity of approximately 36.0 mgCd g−1biomass. FTIR analysis showed that nitrogen limitation induced changes in the composition of the outer cell wall, specifically an increase of deacetlylated polysaccharides, reducing the relative amount of secondary amines and proteins from the peptidoglycan matrix. Amino groups from acetylated polysaccharides and proteins have been associated elsewhere with greater cadmium affinity, which could explain the poor results obtained with the nitrogen-restricted biomass. This study shows that new physiological states displaying different adsorption capabilities were effectively obtained by engineering the cell coverage of the bacteria using varying culture strategies. The fed-batch culture proved to be a valuable tool for studying PGPR strains for biosorption and other applications. Exploring diverse nutrient limitations and other pollutants in this bacterium and other members of the PGPR family offer great opportunities to tailor biosorption strategies based on specific conditions, ultimately contributing to sustainable environmental solutions.

Functionalization strategy of carboxymethyl cotton gauze fabrics with zeolitic imidazolate framework-67 (ZIF-67) as a recyclable material for biomedical applications

The accumulation of uremic toxins in the human body poses a deadly risk because it causes chronic kidney disease. To increase the effectiveness of hemodialysis and raise the survival rate, these toxins must be effectively removed from the bloodstream. Developing effective materials for removing these dangerous substances requires a thorough understanding of the interactions between an adsorbent and the uremic toxins. Thankfully, metal-organic frameworks (MOFs) have shown considerable promise for the identification and treatment of kidney disorders. Herein, cotton gauze fabrics (CGF) were carboxylated using monochloroacetic acid to produce carboxymethylated cotton gauze fabrics (CM-CGF). CM-CGF was subsequently decorated in situ with zeolitic imidazolate framework-67, resulting in carboxymethylated cotton gauze fabrics-zeolitic imidazolate framework-67 (CM-CGF-ZIF). The CGF, CM-CGF, and CM-CGF-ZIF were evaluated for potential kidney applications by removing uric acid and creatinine from mimic blood. The results showed that CM-CGF-ZIF had the highest adsorption of uric acid and creatinine. The maximum adsorption capacity of uric acid and creatinine was 164 and 222 mg/g for CM-CGF-ZIF, respectively, compared to 45 and 67 mg/g for CGF. CM-CGF-ZIF showed excellent antibacterial activity, good antifungal activity, low cytotoxicity, and a satisfactory level of blood compatibility.