Cooperative adsorption on solid surfaces

Kinetics, Thermodynamics, and Mechanistic Studies of Arsenic Removal Utilizing Natural Soil as Adsorbent

The contamination of water sources with the heavy metal contaminant arsenic (As) causes substantial risks to humans, animals, and other living organisms. Therefore, the introduction of methods for the removal of As is important. The present study aimed to investigate the adsorption model and mechanism of As removal utilizing natural soil adsorbents. The batch adsorption technique was used to analyze the impacts of various parameters such as contact time, initial As concentration, pH, and temperature. Adsorption mechanisms were studied through adsorption kinetic, isotherm, and thermodynamic models. The batch adsorption study findings indicate that the optimal conditions for maximum As removal were achieved by application of 2.2 g of adsorbents in 50 μg/L of As solution for 60 min of contact time at a pH of 5.5 ± 0.5 and a temperature of 40 °C. The highest removal efficiency was achieved when red soil was employed as the adsorbent. The kinetic, isotherm, and thermodynamic models revealed that As adsorption was a chemisorptive, nonspontaneous, and endothermic process.

Cation Dependence of Enniatin B/Membrane-Interactions Assessed Using Surface-Enhanced Infrared Absorption (SEIRA) Spectroscopy

Enniatins are mycotoxins with well-known antibacterial, antifungal, antihelmintic and antiviral activity, which have recently come to attention as potential mitochondriotoxic anticancer agents. The cytotoxicity of enniatins is traced back to ionophoric properties, in which the cyclodepsipeptidic structure results in enniatin:cation-complexes of various stoichiometries proposed as membrane-active species. In this work, we employed a combination of surface-enhanced infrared absorption (SEIRA) spectroscopy, tethered bilayer lipid membranes (tBLMs) and density functional theory (DFT)-based computational spectroscopy to monitor the cation-dependence (Mz+=Na+, K+, Cs+, Li+, Mg2+, Ca2+) on the mechanism of enniatin B (EB) incorporation into membranes and identify the functionally relevant EBn : Mz+ complexes formed. We find that Na+ promotes a cooperative incorporation, modelled via an autocatalytic mechanism and mediated by a distorted 2 : 1-EB2 : Na+ complex. K+ (and Cs+) leads to a direct but less efficient insertion into membranes due to the adoption of "ideal" EB2 : K+ sandwich complexes. In contrast, the presence of Li+, Mg2+, and Ca2+ causes a (partial) extraction of EB from the membrane via the formation of "belted" 1 : 1-EB : Mz+ complexes, which screen the cationic charge less efficiently. Our results point to a relevance of the cation dependence for the transport into the malignant cells where the mitochondriotoxic anticancer activity is exerted.

Large-area grown ultrathin molybdenum oxides for label-free sensitive biomarker detection

The rise of two-dimensional (2D) materials has provided a confined geometry and yielded methods for guiding electrons at the nanoscale level. 2D material-enabled electronic devices can interact and transduce the subtle charge perturbation and permit significant advancement in molecule discrimination technology with high accuracy, sensitivity, and specificity, leaving a significant impact on disease diagnosis and health monitoring. However, high-performance biosensors with scalable fabrication ability and simple protocols have yet to be fully realized due to the challenges in wafer-scale 2D film synthesis and integration with electronics. Here, we propose a molybdenum oxide (MoOx)-interdigitated electrode (IDE)-based label-free biosensing chip, which stands out for its wafer-scale dimension, tunability, ease of integration and compatibility with the complementary metal-oxide-semiconductor (CMOS) fabrication. The device surface is biofunctionalized with monoclonal anti-carcinoembryonic antigen antibodies (anti-CEA) via the linkage agent (3-aminopropyl)triethoxysilane (APTES) for carcinoembryonic antigen (CEA) detection and is characterized step-by-step to reveal the working mechanism. A wide range and real-time response of the CEA concentration from 0.1 to 100 ng mL-1 and a low limit of detection (LOD) of 0.015 ng mL-1 were achieved, meeting the clinical requirements for cancer diagnosis and prognosis in serum. The MoOx-IDE biosensor also demonstrates strong surface affinity towards molecules and high selectivity using L-cysteine (L-Cys), glycine (Gly), glucose (Glu), bovine serum albumin (BSA), and immunoglobulin G (IgG). This study showcases a simple, scalable, and low-cost strategy to create a nanoelectronic biosensing platform to achieve high-performance cancer biomarker discrimination capabilities.

Carbon Dot-Stabilized Hydrogel Composite: A New Adsorbent for Efficient and Sustainable Pb(II) Removal

In this paper, a carbon dot hydrogel composite (CDs-Hy) capable of efficiently removing Pb(II) was prepared by hydrogen bonding self-assembly in combination with carbon dots and a hydrogel. CDs-Hy was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and the effect of the adsorption conditions on the adsorption efficiency of CDs-Hy was studied. The results of the study showed that the incorporation of carbon dots, on the one hand, significantly increased the adsorption capacity of the material. On the other hand, it can increase the stability of hydrogels in aqueous solution. The possible adsorption mechanisms were further verified as ion exchange and coordination. CDs-Hy is a novel adsorbent material capable of removing Pb2+ efficiently, which can be reused several times with high stability.

On the origin of cooperativity effects in the formation of self-assembled molecular networks at the liquid/solid interface

In this work we investigate the behaviour of molecules at the nanoscale using scanning tunnelling microscopy in order to explore the origin of the cooperativity in the formation of self-assembled molecular networks (SAMNs) at the liquid/solid interface. By studying concentration dependence of alkoxylated dimethylbenzene, a molecular analogue to 5-alkoxylated isophthalic derivatives, but without hydrogen bonding moieties, we show that the cooperativity effect can be experimentally evaluated even for low-interacting systems and that the cooperativity in SAMN formation is its fundamental trait. We conclude that cooperativity must be a local effect and use the nearest-neighbor Ising model to reproduce the coverage vs. concentration curves. The Ising model offers a direct link between statistical thermodynamics and experimental parameters, making it a valuable tool for assessing the thermodynamics of SAMN formation.

Revealing the Origin of Cooperative Adsorption of Chains on Nanoparticle Surfaces through Coarse-Grained Simulations

This work aims to deepen our understanding of the molecular origin of the recently observed phenomenon of polymer cooperative adsorption onto faceted nanoparticle (NP) surfaces. By exploring a large parameter space for polymer/NP interactions through coarse-grained (CG) molecular dynamics (MD) simulations, it is found that consistent with experiments the presence or absence of cooperativity is related to solvent quality and relative interaction strengths between the polymer and the adsorbent. Specifically, positive cooperativity is associated with stronger polymer-polymer interaction than polymer-surface interactions and vice versa for negative cooperativity. This contrast in interaction energies manifests in positive cooperativity (i.e., increased affinity) and negative cooperativity (i.e., decreased affinity) as concentration increases. It is also found that increasing chain length strengthens cooperativity effects and that the nanoscale confinement of polymer chains to the adsorbing facet (due to weaker affinity to corners and edges) enhances positive cooperativity but weakens negative cooperativity. Moreover, adsorption onto a spherical NP shows stronger positive cooperativity but weaker negative cooperativity compared with adsorption onto a cubic NP of equal surface area. It was further found that as polymer bulk concentration increases, the free energy of adsorption decreases in positive cooperativity, increases in negative cooperativity, and is independent of concentration in noncooperative systems consistent with the phenomenological explanation of cooperativity. We further found that positive cooperativity is associated with growing fluctuations in the adsorption density at critical bulk polymer concentrations. This behavior can be attributed to the competition between enthalpic gains and entropic losses upon adsorption. Overall, our results shed light on the microscopic origin of cooperative adsorption and the role of solvent quality, which can be leveraged in, for example, controlling NP growth into target shapes and designing NP catalysts with improved performance.

Preparation of ionic liquid modified graphene composites and their adsorption mechanism of arsenic (V) in aqueous solution

Graphene (GR) is a new type of carbon-based material that combines many excellent properties. In order to give full play to the excellent properties of graphene and expand its application scope, this study used ionic liquid SbF6 to modify it and successfully prepared ionic liquid modified graphene composites (H/GR), and studied its adsorption mechanism of arsenic in aqueous solution. By investigating the effects of reaction temperature, reaction time, pH, adsorbent (H/GR) dosage, and humic acid concentration on the removal rate of arsenic in aqueous solution, the experimental results showed that when the reaction temperature was 30 °C, reaction time was 1 h, pH was 6, H/GR dosage was 0.1g·L-1, and humic acid (HA) concentration was 10 mg·L-1, the best arsenic removal effect was achieved with a maximum. The removal rate was 99.4%. The equilibrium adsorption capacity was well modeled by the Langmuir, Freundlich, and Tenkin models at 30 °C. The Langmuir adsorption isotherm was the most consistent, with a calculated maximum value of 137.95 mg·g-1, which is higher than most adsorbents in the field. In addition, it was determined that the graphene surface was indeed immobilized with the ionic liquid [Hmim]SbF6 by SEM mapping and EDS energy spectroscopy observation, and the adsorption isotherms and pore size distribution maps of graphene before and after the loading of the ionic liquid were analyzed by BET, which further confirmed a significant increase in the microporosity and porosity of the modified H/GR, and furthermore, it was demonstrated that the arsenic ions are chemically bonded with and indeed adsorbed on the surface of the H/GR by FT-IR and XPS characterization analyses. The results of all experimental data studies indicate that the main mechanism of As(V) removal from water by H/GR is due to electrostatic adsorption, ion exchange, and complexation between the modified graphene itself and the ionic liquid [Hmim]SbF6 itself.

A novel ZIF-8@IL-MXene/poly (N-isopropylacrylamide) nanocomposite hydrogel toward multifunctional adsorption

Phenols, dyes, and metal ions present in industrial wastewater can adversely affect the environment and leach biological carcinogens. Given that the current research focuses only on the removal of one or two of those categories. Herein, this work reports a novel ZIF-8@IL-MXene/Poly(N-isopropylacrylamide) (NIPAM) nanocomposite hydrogel that can efficiently and conveniently absorb and separate multiple pollutants from industrial wastewater. Ionic liquid (IL) was grafted onto MXene surfaces using a one-step method, and then incorporated into NIPAM monomer solutions to obtain the IL-MXene/PNIPAM composite hydrogel via in-situ polymerization. ZIF-8@IL-MXene/PNIPAM nanocomposite hydrogels were obtained by in-situ growth of ZIF-8 on the pore walls of composite hydrogels. As-prepared nanocomposite hydrogel showed excellent mechanical properties and can withstand ten repeated compressions without any damage, the specific surface area increased by 100 times, and the maximum adsorption capacities for p-nitrophenol (4-NP), crystal violet (CV), and copper ion (Cu2+) were 198.40, 325.03, and 285.65 mg g-1, respectively, at room temperature. The VPTTs of all hydrogels ranged from 33 to 35 °C, so the desorption process can be achieved in deionized water at 35-40 °C, and its adsorption capacities after five adsorption-desorption cycles decreased to 79%, 91%, and 29% for 4-NP, CV, and Cu2+, respectively. The adsorption data fitting results follow pseudo-second-order kinetics and Freundlich models, which is based on multiple interactions between the functional groups contained in hydrogels and adsorbent molecules. The hydrogel is the first to realize the high-efficiency adsorption of phenols, dyes and metal ions in industrial wastewater simultaneously, and the preparation process of hydrogels is environmentally friendly. Also, giving hydrogel multifunctional adsorption is beneficial to promote the development of multifunctional adsorption materials.

Adsorptive removal of heavy metals from wastewater using Cobalt-diphenylamine (Co-DPA) complex

Heavy metals like Cadmium, Lead, and Chromium are the pollutants emitted into the environment through industrial development. In this work, a new diphenylamine coordinated cobalt complex (Co-DPA) has been synthesized and tested for its efficiency in removing heavy metals from wastewater, and its adsorption capacity was investigated. The effectiveness of heavy metals removal by Co-DPA was evaluated by adjusting the adsorption parameters, such as adsorbent dose, pH, initial metals concentration, and adsorption period. Heavy metal concentrations in real sample were 0.267, 0.075, and 0.125 mg/L for Cd2+, Pb2+, and Cr3+ before using as-synthesized Co-DPA to treat wastewater. After being treated with synthesized Co-DPA the concentration of heavy metals was reduced to 0.0129, 0.00028, 0.00054 mg/L for Cd2+, Pb2+, and Cr3+, respectively, in 80 min. The removal efficiency was 95.6%, 99.5%, and 99.5% for the respective metals. The adsorption process fitted satisfactorily with Freundlich isotherm with R2(0.999, 0.997, 0.995) for Cd2+, Pb2+, and Cr3+, respectively. The kinetic data obeyed the pseudo-second order for Cd2+ and Cr2+ and the pseudo-first order for Pb2+. Based on the results obtained within the framework of this study, it is concluded that the as-synthesized Co-DPA is a good adsorbent to eliminate heavy metal ions like Cd2+, Pb2+, and Cr3+from wastewater solution. In general, Co-DPA is a promising new material for the removal of heavy metal ions from water.

Thermodynamic and Kinetic Equilibrium for Adsorption of Cellulosic Xylose of Commercial Cation-Exchange Resins

The development of low-cost purification technology is an indispensable need for industrial biorefinery. Xylose is easily obtained from hydrothermal pretreatment of lignocellulosic biomass. This current study emphasizes the chromatographic monosaccharide separation process using commercial cation-exchange resins (CER) including Amberlite 120 and Indion 225 to separate xylose from a mixture of hydrolysates. To understand the performance of the two CER, the studies of equilibrium, thermodynamics, and kinetics were evaluated. In this study, with different xylose concentrations, the adsorption equilibrium was found to follow the Freundlich isotherm model well (R2 > 0.90 for both CER). The results indicated that a pseudo-second-order model represented the xylose adsorption kinetics. In addition, the activation energy of xylose adsorption onto both CER, i.e., Amberlite 120 and Indion 225 was 34.9 and 87.1 kJ/mol, respectively. The present adsorption studies revealed the potential of these commercial CER to be employed as effective adsorbents for monosaccharide separation technology.

Adsorption Affinities of Small Volatile Organic Molecules on Graphene Surfaces for Novel Nanofiller Design: A DFT Study

The adsorption of organic molecules on graphene surfaces is a crucial process in many different research areas. Nano-sized carbon allotropes, such as graphene and carbon nanotubes, have shown promise as fillers due to their exceptional properties, including their large surface area, thermal and electrical conductivity, and potential for weight reduction. Surface modification methods, such as the "pyrrole methodology", have been explored to tailor the properties of carbon allotropes. In this theoretical work, an ab initio study based on Density Functional Theory is performed to investigate the adsorption process of small volatile organic molecules (such as pyrrole derivatives) on graphene surface. The effects of substituents, and different molecular species are examined to determine the influence of the aromatic ring or the substituent of pyrrole's aromatic ring on the adsorption energy. The number of atoms and presence of π electrons significantly influence the corresponding adsorption energy. Interestingly, pyrroles and cyclopentadienes are 10 kJ mol-1 more stable than the corresponding unsaturated ones. Pyrrole oxidized derivatives display more favorable supramolecular interactions with graphene surface. Intermolecular interactions affect the first step of the adsorption process and are important to better understand possible surface modifications for carbon allotropes and to design novel nanofillers in polymer composites.

Synthesis & fabrication of O-linked polymeric hybrids for recovery of textile dyes: Closed loop economy

Dyes are an important resource employed for the production systems in textile, paper, paint and leather industry. An estimate of 200,000 tons of dyes are discharged as textile effluent each year worldwide. It becomes imperative to recover these dyes by treating the effluents using economically viable routes. The present research was undertaken with the objective to attain zero emission and zero waste through development of novel polymeric hybrids as adsorbents. For this purpose, metal moieties (Al3+, Si4+, Ti4+ and Zr4+) were hybridized with polyacrylic acid, and cellulose acetate for the uptake of selected dyes under optimized parameters. The structural elucidation of four synthesized hybrids (MP-Al, MP-Si, MP-Ti and MP-Zr) by FTIR, EDX and TGA confirmed O-linked grafting of metal moieties with polymers and thermally stable porous materials. SEM micrographic images displayed void spaces providing channels for effective adsorption. The batch experiments demonstrated removal of malachite green (77-96%) and congo red (70-82%) upon contact of initial 45 min on polymeric hybrids On the other hand, pristine polyacrylic acid and cellulose acetate showed remarkably low removal of dyes. The adsorption mechanism is proposed as physical in nature following type II isotherm. Further, Langmuir and Ho's pseudo second order fitness was evaluated. In order to determine the economic viability of the present research, the real textile dyes were recovered in three consecutive cycles of adsorption and chemical treatment of hybrids. The results propose a system with positive impact on economy by maximum utilization of hybrids as adsorbents and recovery of textile dyes for reuse in textile processing.

Prewetting Electron Beam Irradiated and Native Sheep Wool Can Affect Their Sorptivity

In this work, the effect of prewetting native and electron beam-modified wool on the resulting sorption of Cu(II) from wool solutions was studied. The following conditions and combinations were applied: 6 mM and 50 mM solutions, prewetting time 0-24 h, contact time 1-24 h. The sorption results showed that wetting the wool before sorption from the low concentrated solution can fundamentally improve the efficiency of the separation process. The opposite result was achieved when applying a more concentrated solution; that is, prewetting slightly reduced the sorptivity. The reasons for such results are discussed. The application of these findings can be used to optimize the separation process in technological practice, however, will require solute specification.

Bifunctional collagen fiber/carbon quantum dot fluorescent adsorbent for efficient adsorption and detection of Pb2

In this work, fluorescent adsorbents that can efficiently detect and remove Pb²⁺ were developed by integrating the designed amino-modified carbon quantum dots and carboxyl-modified collagen. The adsorption properties of the fluorescent adsorbent were further optimized and analyzed using a series of response surface experiments. The maximum adsorption concentration for Pb²⁺ was 183 mg.g^-1. The adsorption isotherms fit well with the Langmuir model, and the adsorption kinetics fit with the pseudo-second-order model. The emission intensity of the fluorescent adsorbent gradually decreased with the increase of the concentration of Pb²⁺, and had a good linear correlation. In addition, the mechanism of detection and removal of Pb²⁺ by fluorescent adsorbents was further demonstrated. The novel three-dimensional structured fluorescent aerogel can be used as a promising adsorbent with good adsorption concentration and sensing ability for Pb²⁺, which shows great prospects in wastewater.

Competitive Cation Adsorption on Electron-Irradiated Sheep Wool Changes the Fitting of Adsorption Isotherms for Single-Component Solutions

This work analyses 10 adsorption isotherm models applied to adsorption of Cr(III) and Cu(II) from binary solutions on electron-irradiated sheep wool (0-24-100) kGy. The results are compared with fitting the same adsorbates from corresponding single solutions. The competing cation significantly changes the fitting of the selected isotherms to the extent that even simultaneous fitting of the same cation in the single and binary solution is rare. In the case of Cr(III), 4 favourable matches were found out of 30 compared cases, while in the case of Cu(II), only 2 conformities were found. Having the Cr(III) coordination number exclusively of 6, but Cu(II) up to 4, 5, 6, the last coordinates more easily with the ligands provided by keratin, resulting in preferential chemisorption. If there is still a lack of cysteic acid in the wool to interact with Cr(III) also, this is adsorbed on the wool physically, too. The amount of cysteic acid increasing in the wool with the absorbed dose of energy improves the chemisorption of Cr(III), as well. It can be summarized that during competitive adsorption, Cu(II) binds by chemisorption and Cr(III) by both physisorption and chemisorption, depending on the dose of energy absorbed by the wool.

Adsorption and immobilization performance of pine-cone pristine and engineered biochars for antimony in aqueous solution and military shooting range soil: An integrated novel approach

Antimony (Sb-V), a carcinogenic metalloid, is becoming prevalent in water and soil due to anthropogenic activities. Biochar could be an effective remedy for Sb(V)-contaminated water and soil. In this study, we used pristine and engineered pinecone-derived biochar as an innovative approach for treating Sb(V)-contaminated water and shooting range soil. Biochar was produced from pine-cone waste (pristine biochar) and enriched with Fe and Al salts via saturation (engineered biochar). Adsorption tests in water revealed that iron-modified biochar showed higher adsorption capacity (8.68 mg g^-1) than that of the pristine biochar (2.49 mg g^-1) and aluminum-modified biochar (3.40 mg g^-1). Isotherm and kinetic modeling of the adsorption data suggested that the adsorption process varied from monolayer to multilayer, with chemisorption as the dominant interaction mechanism between Sb(V) and the biochars. The post-adsorption study of iron-modified biochar by Fourier Transform Infrared (FTIR) and X-ray diffraction (XRD) further supported the chemical bonding and outer-sphere complexation of Sb(V) with Fe, N-H, O-H, C-O and CC components. The pristine and iron-modified biochars also successfully immobilized Sb(V) in a shooting range soil, more so in the latter. Subsequent sequential extractions and post-analysis by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and elemental dot mapping revealed that Sb in the treated soil transformed to a more stable form. It was concluded that iron-modified biochar could act as an efficient material for the adsorption and immobilization of Sb(V) in water and soil, respectively.

Synthesis, Characterization and Investigation of Cross-Linked Chitosan/(MnFe2O4) Nanocomposite Adsorption Potential to Extract U(VI) and Th(IV)

A cross-linked chitosan/(MnFe2O4) CCsMFO nanocomposite was prepared using co-precipitation methods and used as a nanomaterial to extract U(VI) and Th(IV) from an aqueous solution based on adsorption phenomena. The contact time of experiments shows a rapid extraction process within 30 min by the CCsMFO nanocomposite. The solution pH acts a critical role in determining qm value, where pH 3.0 was the best pH value to extract both ions. The pseudo-second-order equilibrium model illustrated the kinetics equilibrium modal extraction process. Adsorption isotherm of U(VI) at pH 3.0 by CCsMFO nanocomposite is an endothermic process. In contrast, the adsorption isotherm of Th(IV) at pH 3.0 by CCsMFO nanocomposite is an exothermic process. The reusability of CCsMFO nanocomposite was tested using basic eluents as suitable conditions for the chemical stability of CCsMFO nanocomposite; the reusability results show promising results for the removal of U(VI) adsorbed onto CCsMFO nanocomposite with 77.27%, after 12 h by Na2CO3 as eluent. At the same time, the reusability results show good reusability for removal of U(VI) adsorbed onto CCsMFO nanocomposite with 21.82%, after 8 h by EDTA as eluent.

Ionic liquid decorated MXene/Poly (N-isopropylacrylamide) composite hydrogel with high strength, chemical stability and strong adsorption

Organic phenolic pollutants in industrial wastewater cause severe environmental pollution and physiological damage. Poly (N-isopropylacrylamide) (PNIPAM) hydrogels generally have poor mechanical strength and are also intrinsically frangible, limiting their widespread applications in wastewater treatment. Combining them with 2-dimensional materials can also only improve the mechanical properties of hydrogels. Here, we report a high-strength, chemical stability and strong adsorption MXene/poly (N-isopropylacrylamide) (PNIPAM) thermosensitive composite hydrogel for efficient removal of phenolic pollutants from industrial wastewater. Ionic liquids (ILs) were grafted onto the surface of MXenes and introduced into NIPAM monomer solution to obtain composite hydrogels by in-situ polymerization for improved mechanical strength and adsorption capacity of the composite hydrogel. Compared with the MXene/PNIPAM composite hydrogel, the introduction of ILs simultaneously improves the mechanical and adsorption properties of the composite hydrogel. The ILs bind to the surface of MXene flakes through electrostatic interactions, which improved the thermal stability and oxidation resistance of MXenes while maintaining its good dispersion. Using 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified MXene (MXene-EMIMBF4) did not change significantly were observed after aging for 45 days. As-prepared composite hydrogels demonstrated excellent mechanical properties, reusability, and high adsorption capacity for p-Nitrophenol (4-NP). The MXene-EMIMBF4/PNIPAM hydrogel could recover after ten 95% strain compression cycles under the synergistic effect of chemical bonding and electrostatic attraction. Its maximum adsorption capacity for 4-NP was 200.29 mg g^-1 at room temperature, and the adsorption capacity maintained at ∼90% of its initial value after five adsorption cycles, which was related to the introduction of EMIMBF4 to form a denser network structure. The adsorption data followed the pseudo-second-order kinetics and Freundlich models.

Effectiveness of the engineered pinecone-derived biochar for the removal of fluoride from water

Drinking fluoride (F^-)-contaminated water (>1.5 mg L^-1) causes severe dental and skeletal disorders. In the central province of Pakistan, ∼20 times higher levels of F^- in the drinking groundwater (compared with the 1.5 mg L^-1 permissible limit of the World Health Organization) are triggering bone abnormalities in teenagers. In this study, we demonstrated the potential of pinecone-derived biochar (pristine) impregnated with Fe- and Al-salts (engineered) to defluoridate water. Batch mode adsorption experiments were carried out under variable conditions of solution pH, F^- initial concentration, adsorbent dose, and contact time. The engineered biochars resulted in greater adsorption than that of pristine biochar. Specifically, the AlCl₃-modified biochar exhibited a maximum adsorption capacity of 14.07 mg g^-1 in spiked water and 13.07 mg g^-1 in in-situ groundwater. The equilibrium isothermal and kinetic models predicted monolayer, cooperative, and chemisorption types of the adsorption process. The chemical interaction and outer-sphere complexation of F^- with Al, Na, and H elements were further confirmed by the post-adsorption analysis of the AlCl₃-modified biochar by FTIR and XRD. The AlCl₃-modified biochar resulted in 87.13% removal of F^- from the in-situ F^--contaminated groundwater, even in the presence of naturally occurring competing ions (such as Cl^-, HCO₃^-, SO₄^2-, and NO₃^-). We conclude that the AlCl₃-modified biochar derived from pinecone could be a promising cost-effective adsorbent for the defluoridation of water.

Genetically modified metallothionein/cellulose composite material as an efficient and environmentally friendly biosorbent for Cd2+ removal

Metallothioneins (MTs) are a class of cysteine-rich metal-binding proteins. Cadmium (Cd) is one of the toxic heavy metal pollutants. In our previous research, the full-length cDNA of MT (Cd specificity) from freshwater crab (Sinopotamon henanense) (ShMT) was cloned and genetically modified to ShMT3 by site-directed mutagenesis to enhance the tolerance for Cd²⁺, however, it was limited in actual Cd²⁺ adsorption due to instability. Here, ShMT3-CBM, a novel recombinant fusion protein, was prepared. CBM is a carbohydrate binding module that can specifically bind cellulose while ShMT3 can effectively chelate Cd²⁺. The biosorbent Cellulose1-ShMT3-CBM was obtained by screening suitable cellulose materials. The selective adsorption experiments showed that Cellulose1-ShMT3-CBM had a preference for Cd²⁺. In low-concentration Cd²⁺ solutions, the removal efficiency was >99 %, and the adsorption equilibrium was reached within 15 min. The saturated adsorption capacity of Cellulose1-ShMT3-CBM for Cd²⁺ is 180.35 ± 4.67 mg/g (Dry Weight). Regeneration experiments showed that adsorption efficiency was maintained after six cycles. The MTT experiment showed that Cellulose1-ShMT3-CBM had low cytotoxicity. Meanwhile, Cellulose1-ShMT3-CBM can preferentially remove Cd²⁺ in actual water samples and boiler sewage. In this study, an environmentally friendly biosorbent which can adsorb Cd²⁺ efficiently and quickly was prepared for actual water treatment.

Trace element adsorption from acid mine drainage and mine residues on nanometric hydroxyapatite

Mining Ag, Cu, Pb, and Zn sulfides by flotation produces great volume of residues, which oxidized through time and release acid solutions. Leachates from tailing heaps are a concern due to the risk of surface water pollution. Hydroxyapatite nanoparticles may remove trace elements from acid leachate collected from an oxidized tailing heap (pH ranged 1.69 ± 0.3 to 2.23 ± 0.16; [SO₄^2-] = 58 ± 0.67 to 60.69 ± 0.39 mmol). Based on the batch experiments under standard conditions, the average removal efficiency was 96%, 92%, 86%, and 67% for Cd, Pb, Zn, and Cu, respectively. The Zn adsorption was modeled by the Freundlich equation, but Cd, Cu, and Pb isotherms do not fit to Freundlich nor Lagmuir equations. Adsorption and other mechanisms occur during trace elements removal by hydroxyapatite. In the polymetallic system, trace elements saturate the specific surface of hydroxyapatite in the following order Zn, Cd, Cu, and Pb. The pH values must be higher than 7.5 to adsorb trace elements. The dose of 3.8% of hydroxyapatite to acid mine drainage removed efficiently > 80% of the soluble Fe, Cu, Mn, Zn, Cd, Ni, and Pb: 4020.0, 37.3, 34.8, 432.0, 4.4, 0.7, and 0.11 mg L^-1 from leachate A and 3357.1, 46.6, 27.8, 569.0, 4.7, 0.6, and 1.7 from leachate B, respectively. The application of 0.7% of hydroxyapatite decreased the extractable Pb in unoxidized tailing heaps from 272 to 100 mg kg^-1. It is likely to use hydroxyapatite to control trace element mobility from mine residues to surrounding soils and surface water.

Use of a new zwitterionic cellulose derivative for removal of crystal violet and orange II from aqueous solutions

This study describes the synthesis of a new bioadsorbent with zwitterionic characteristics and its successful application for removal of a cationic dye (crystal violet, CV) and an anionic dye (orange II, OII) from single component aqueous systems. The new bi-functionalized cellulose derivative (MC3) was produced by chemical modification of cellulose with succinic anhydride and choline chloride to introduce carboxylic and quaternary ammonium functional groups on the cellulose surface. MC3 was characterized by several wet chemical and spectroscopic methods. The effects of solution pH, contact time, and initial solute concentration on removal of CV and OII by MC3 were investigated. Studies of the desorption and re-adsorption of the dyes were also carried out. The isotherms for adsorption of CV and OII on MC3 were satisfactorily fitted using the Konda and Langmuir models. MC3 showed experimental maximum adsorption capacities of 2403 mg g^-1 for CV and 201 mg g^-1 for OII. The desorption and re-adsorption results showed that MC3 could be reused in successive adsorption cycles, which is essential for minimizing process costs and waste generation. The findings showed that MC3 is a versatile biosorbent capable of efficiently removing both cationic and anionic dyes.

Interactions of Anti-Inflammatory and Antibiotic Drugs at Mineral Surfaces Can Control Environmental Fate and Transport

Various pharmaceutical compounds often coexist in contaminated soils, yet little is known about how their interactions impact their mobility. We here show that two typical antibiotic and anti-inflammatory agents (nalidixic acid (NA) and niflumic acid (NFA)) commonly form dimers at several representative soil- and sediment-building minerals of contrasting composition and structure. Cobinding occurs in the form of a NFA-NA dimer stabilized by hydrogen bonding and van der Waals interactions. Using dynamic column experiments containing goethite-coated sand, we then demonstrated that presorbed NA effectively captured the otherwise weakly binding NFA from solution. Simultaneously injecting NA and NFA to presorbed NA enhanced even further both NA and NFA loadings, thereby altering their transport under flow-through conditions. We also showed that environmental level amounts of natural organic matter can reduce the overall retention in column experiments, yet it does not suppress dimer formation. These environmentally relevant scenarios can be predicted using a new transport model that accounts for kinetics and cobinding reactions of NFA onto NA bound to goethite through metal-bonded, hydrogen-bonded, and outer-sphere complexes. These findings have important implications on assessing the fate of coexisting pharmaceutical compounds under dynamic flow conditions in contaminated soils.

Multi-component adsorption study by using bone char: modelling and removal mechanisms

Highly efficient simultaneous removal of paracetamol and Cu²⁺ ions from aqueous solutions was accomplished by using bovine bone char (BC). The adsorption behaviour was determined by kinetic and equilibrium studies of both single and binary system solutions. BC is a predominantly mesoporous material with a surface area of 103 m² g^-1. The influence of the initial pH on Cu²⁺ removal was tested, suggesting that the optimal pH was 3.0. The removal of paracetamol from single and binary systems was 9.45 and 12.7%, respectively. On the other hand, the Cu²⁺ removal was 36.2% for a single system, suggesting a higher affinity for BC. Moreover, in the case of binary mixtures, the presence of paracetamol led to an enhanced affinity of Cu²⁺ due to a synergistic/cooperative mechanism, which led to a copper removal of 97.3%. The cooperative model was successfully adjusted to the equilibrium data of the binary systems. The modelling results indicated the formation of a first adsorption layer where paracetamol and copper are retained, and a second layer with a great affinity for copper ions after the formation of a Cu-paracetamol complex, leading to higher removal of Cu²⁺.

Removal and recovery of phosphate using a novel calcium silicate hydrate composite starch cryogel

Phosphate is a major pollutant that deteriorates water quality and causes eutrophication, a novel calcium silicate hydrate composite cryogel (Cry-CSH) was thus successfully prepared for phosphate removal and recovery in this work. Calcium silicate hydrate (C-S-H) was mixed with the gel precursor (7.5% w/w) prepared from native starch and limewater (saturated calcium hydroxide solution as the cross-linker). The mixture was frozen and thawed for 3 cycles giving an interconnected macroporous composite. This had C-S-H nanoparticles (75 mg) immobilized on a monolithic floatable cryogel network (2.5 cm diameter × 1.0 cm height) enabling an easier recovery and without the losses that occur when using C-S-H nanoparticles. The phosphate adsorption reaches equilibrium at 120 min with adsorption capacity of 2.50 mgPO₄^3-/g_Cry-CSH (65.42 mgPO₄^3-/g_C-S-H) under optimum conditions. Adsorption equilibrium data were well fit by the Freundlich isotherm model, while kinetic results were well fit by the pseudo second-order model. The calculated activation energy (E_a) of 43.9 kJ/mol indicates chemical adsorption, while a positive change in enthalpy (ΔH⁰, 19.3 kJ/mol) indicates the endothermic nature of phosphate adsorption. Cry-CSH can remove phosphate from wastewater and effluent samples with excellent removal efficiency (>98%). It can float on water surface for at least 105 days without damage, while its phosphate adsorbed form can be biodegraded within 10 days under soil buried conditions. Thus, this work demonstrated the significant potential of Cry-CSH for practical and environmentally friendly phosphate removal and recovery.

The Dependency of Kinetic Parameters as a Function of Initial Solute Concentration: New Insight from Adsorption of Dye and Heavy Metals onto Humic-Like Modified Adsorbents

Kinetics parameters are the essential issue in the design of water treatment systems for pollutants uptake. Though numerous studies have identified the boundary conditions that exert influence on the kinetics parameters, the influence of the dynamic initial solute concentration (C0) to the kinetic parameters generated from fitting kinetics model to experimental data has not been investigated thoroughly. This study revealed a change in the kinetics parameter value due to changes in the adsorption mechanism as an effect of dynamic C0. It was observed that at higher C0 the adsorbed solute at equilibrium (qe) increases and it takes longer time to reach equilibrium. As a result, the kinetics rate constant (k) calculated from adsorption reaction model (Lagergren, Ho, Santosa, and RBS) was decreased. In general, Ho model exhibit higher correlation coefficient value (R2) among the other model at low C0. At high C0, Ho’s R2 tend to decrease while the Lagergren and RBS’s R2 was increased. The amendment mechanism from external mass transport to intra-particle diffusion as a rate limiting step was evidenced by Boyd and Weber-Morris kinetics model. Further, the physicochemical properties of the adsorbent used in this work: chitin and Fe3O4 modified horse dung humic acid (HDHA-Fe3O4 and HDHA-Ch, respectively) with the solute: Pb(II), Methylene Blue (MB), and Ni(II) was deeply discussed in this paper. The outcomes of this work are of prime significance for effective and optimum design for pollutant uptake by adsorption equipment. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Adsorption of benzene and toluene from aqueous solution using a composite hydrogel of alginate-grafted with mesoporous silica

Hydrogels are often claimed as optimal adsorbents for water treatment; however, their efficiency towards the removal of hydrophobic pollutants is still limited. As an alternative, hydrogels prepared from polymers functionalized with siliceous materials can overcome this issue. Here, a composite hydrogel (denoted as GEL-SBA15) was prepared using alginate grafted with mesoporous silica (SBA15) and poly(vinyl alcohol) for benzene and toluene adsorption from aqueous solutions. Adsorption studies demonstrated that a low dosage of GEL-SBA15 (10 mg) has a high adsorption capacity for benzene (1482.8 mg/g) and toluene (596.6 mg/g) under mild experimental conditions (pH 7.0, at 25 °C). Besides, the adsorption capacities of GEL-SBA15 for both pollutants were enhanced compared to the conventional hydrogel. Kinetic analysis showed that the adsorption of benzene and toluene follows a pseudo-second order model, while the experimental adsorption data were well-fitted by the Freundlich isotherm. According to this isotherm, the adsorption occurs via a collaborative process, and weak physical forces (π-π interactions, van der Waals and hydrophobic) are involved. Hence, the post-utilized GEL-SBA15 can be recycled and reused up to 6 times without losing adsorption performance. Although hydrogels are not common adsorbents for aromatic hydrocarbons, the results reported here rank GEL-SBA15 as a promising adsorbent for the removal of these pollutants from water.

Application of enzyme-mediated cellulose nanofibers from lemongrass waste for the controlled release of anticancer drugs

In the present study, an application of cellulose nanofibers has been established for the controlled release of an anticancer drug, i.e., camptothecin. The camptothecin is known for its antitumor activity. However, it has certain limitations like instability, low solubility in aqueous solution, and biological fluids. Firstly, the camptothecin was encapsulated into the cellulose nanofiber complex by adjusting the composition ratio of cellulose nanofibers-camptothecin, i.e., 10:3, 10:5, and 10:7. In the 10:3 composition ratio of cellulose nanofibers, camptothecin showed the highest encapsulation efficiency, i.e., 65.28%. The binding of camptothecin with cellulose nanofibers was confirmed by FT-IR analysis. Also, the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm studies demonstrate physical adsorption of camptothecin onto the homogeneous as well as the heterogeneous surface of cellulose nanofibers. Further, the controlled and extended-release profile was observed at different physiological pH, and different kinetics models were used to understand the drug release mechanism. The highest correlation in all pH conditions was obtained in Korsmeyer-Peppas with R² value = 0.93 (pH 1.2), 0.89 (pH 6.8), and 0.97 (pH 7.4), whereas in Higuchi model, R² value = 0.89 (pH 1.2), 0.91 (pH 6.8), and 0.98 (pH 7.4), suggesting the release of a drug via a diffusion mechanism. Hence, the results established that enzyme-mediated cellulose nanofibers may also be an optimal carrier for the controlled drug release formulation without any chemical excipients.

Functionalizing non-smectic clay via methoxy-modification for enhanced removal and recovery of oxytetracycline from aqueous media

Kaolinite and methoxy-modified kaolinite were used as novel adsorbents for oxytetracycline (OTC) removal and recovery from aqueous media. Batch adsorption experiments were performed to study the effect of pH, ionic strengths, initial concentration, and contact time on OTC adsorption. The adsorbents were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after adsorption. Adsorption of OTC reached its maximum when solution pH increased up to 6 for 0.001 M ionic strength, above which adsorption decreased further when solution pH increased. Freundlich and Langmuir's models best fit the equilibrium data with a strong dependency on OTC adsorption capacity giving its maximum at 36 mg g^-1. Binding is postulated for OTC adsorption on pristine kaolinite as a special case of Hill model with independent binding interaction of OTC adsorption onto the clay that affects the adjacent sites on the pristine kaolinite, in contrast with the adsorption of OTC on methoxy-modified kaolinite. Nitrogen peaks of the XPS spectra indicated changes in the oxidation states of C-N bonds in the N1s peaks by forming tertiary amide C-N and methoxy O-CH₃ bonds which corroborated with the results from FTIR spectra. Removal efficiencies and spectroscopic results indicate that performance on methoxy-modified kaolinite is a promising modification on the clay for recovering antibiotics from wastewater.

Sorption Properties of Specific Polymeric Microspheres towards Desethyl-Terbuthylazine and 2-Hydroxy-Terbuthylazine: Batch and Column Studies

This work investigates the sorption properties of poly(divinylbenzene) modified in the Diels-Alder reaction towards persistent and mobile metabolites of terbuthylazine. The batch experiments were carried out to examine the efficiency of desethyl-terbuthylazine and 2-hydroxy-terbuthylazine adsorption on the specific adsorbent and the impact of different factors on the adsorption process. Results fit well to a pseudo-second order kinetic model. It was confirmed that hydrogen bonds play an important role in the studied systems. Five times greater sorption of 2-hydroxy-terbuthylazine than desethyl-terbuthylazine was observed. The molecular structures of both metabolites exhibit complementarity to the arrangement of functional groups in the polymer but the differences in the physicochemical properties of the desethyl derivative make it a highly mobile compound with higher affinity to the aqueous phase. The equilibrium data in the batch study fit the Freundlich isotherm for 2-hydroxy-terbuthylazine, and for desethyl-terbuthylazine the Temkin and Dubinin-Radushkevich models were better. The adsorption capacities obtained under dynamic conditions were comparable with batch results. For column adsorption modeling the Bohart-Adams, Wolborska, Thomas and Yoon-Nelson models were used. The proposed microspheres can be reused easily with no significant decrease in adsorption capacity by using ethanol as eluent in the desorption.

Hierarchical mesoporous zinc-imidazole dicarboxylic acid MOFs: Surfactant-directed synthesis, pH-responsive degradation, and drug delivery

The surfactant template-directed solvothermal method was applied in the synthesis of hierarchical mesoporous zinc-imidazolate derivative metal-organic framework (mesoMOF), which was then utilized for active loading of cisplatin (cis-Pt). To fabricate mesoMOF, various amounts of the surfactant (cetyltrimethylammonium bromide: 0.1-0.3 g) and linker (citric acid: 0.05-0.15 g) were added to the reaction mixture, which resulted in different particle sizes and morphologies. MesoMOF quality attributes such as Specific surface area (SSA), total porous volume, and Barrett-Joyner-Halenda (BJH) pore diameter were also determined. At the optimum reaction condition, mesoMOF with a high surface area (1859 m²/g), pore diameter (14.13 nm) and total pore volume (0.314 cm³/g) was attained. In the next step, cis-Pt was actively loaded in the mesoMOF with a high loading capacity (28% w/w), which was remarkably superior to the microporous MOF. Interestingly, in mildly acidic pH (5.5), mesoMOF underwent degradation, resulting in a rapid release of cis-Pt. Cell viability and apoptosis induction assays confirmed the superiority of the cis-Pt loaded mesoMOF over free drug in a resistant ovarian tumor cell line (A2780cp). Altogether, due to their tunable size and morphology, pH-responsiveness, and acceptable tolerability in mice, the mesoMOFs can be regarded as an anti-cancer drug delivery system.

Comparison of adsorption behaviors of selected endocrine-disrupting compounds in soil

Bisphenol-A (BPA), 17α-ethinylestradiol (EE2), and 4-nonylphenol (4NP) are endocrine-disrupting chemicals (EDCs) that are useful models for studying the potential fate and transport of EDCs in soil and water environments. Two alluvial soils with contrasting physicochemical properties were used as adsorbents for this study. The Zook soil material had more organic matter and clay than the sandy loam Hanlon soil material. Batch equilibrium experiments were performed to generate adsorption isotherms, to determine the adsorption parameters, and to assess desorption hysteresis. Adsorption of BPA to both soils followed an L-type isotherm, and 4NP adsorbed to both Hanlon and Zook soils exhibited S-shape isotherms. EE2 adsorbed to the Zook soil also followed an S-shaped isotherm, but EE2 adsorbed to the Hanlon soil showed an H-type isotherm. Overall, the Sips model fit the data well, with standard errors of prediction generally ≤6%. The adsorption affinity (K_LF ) values were highest for 4NP, and BPA had the lowest hysteresis indices. The data suggest that BPA was most likely adsorbed by soil organic matter via hydrogen bonding involving its two phenolic groups. In contrast, isotherm shape, model affinity indices, lack of desorption, and molecular-scale characteristics led us to infer that 4NP was adsorbed largely by the retention of molecular clusters, perhaps in clay nanopores. Finally, the adsorption of EE2 exhibited different isotherm shapes for the two soils as well as intermediate affinity and desorption indices, suggesting that EE2 molecules could be retained both by soil organic matter and by clay.

Adsorptive Performance of Polypyrrole-Based KOH-Activated Carbon for the Cationic Dye Crystal Violet: Kinetic and Equilibrium Studies

The aim of this work was to investigate the adsorptive performance of the polypyrrole-based KOH-activated carbon (PACK) in the removal of the basic dye crystal violet (CV) using a batch adsorption system. The equilibrium data, obtained at different initial CV concentrations ( $C_0=50–500\text{mg}/\text{L}$ ) and temperatures (25–45°C), were interpreted using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms, with the Langmuir model providing a better fit ( $R^2\ge 0.9997$ ) and a maximum adsorption capacity of 497.51 mg/g at 45°C. Under the examined conditions, the values of the thermodynamic parameters free energy, enthalpy, and entropy indicate a spontaneous, endothermic, and physisorption adsorption process. The kinetic data of the adsorption process were very well described by a pseudo-second-order model ( $R^2\ge 0.9996$ ). However, surface diffusion seems to be the main rate-controlling step. Thus, we concluded that PACK shows commercial potential for the removal of cationic dyes such as CV from industrial effluent.

Trypan blue removal from water with zein sorbents and laccase

Abstract

Zein-based materials were used to remove Trypan blue from water under flow conditions and in batch tests. In flow tests, zein dissolved at pH = 13 was injected in sand columns and subsequently coagulated with CaCl₂, to create an adsorbent filter which removed over 99% of Trypan blue. Batch tests were conducted using zein powder, zein dissolved at pH = 13 and coagulated with CaCl₂, Fe₂Cl₃ or citric acid, and zein dissolved in ethanol and then coagulated with water. The highest Trypan blue removal was achieved with zein powder (4000 mg Trypan blue/kg sorbent, as determined through spectrophotometry), followed by zein coagulated with Fe₂Cl₃ (500 mg Trypan blue/kg sorbent) and with other salts (140 mg Trypan blue/kg sorbent). Differences in the sorption efficiency are attributed to differences in the surface area. The sorption isotherm of Trypan blue onto zein-based sorbents was a Type II isotherm, suggesting physisorption. Desorption of Trypan blue was limited when zein-based coagulated sorbents were immersed in pure water. Trypan blue could be degraded by free laccase in water, as determined through spectrophotometry and electrospray ionization mass spectroscopy (ESI-MS). Trypan blue could also be degraded by laccase when zein-based laccase-containing sorbents were prepared at pH = 10, using Fe₂Cl₃ as coagulant.

Graphic abstract

Supplementary information

The online version contains supplementary material available at 10.1007/s42452-020-04107-w.

Waste Cleaning Waste: Combining Alginate with Biowaste-Derived Substances in Hydrogels and Films for Water Cleanup

Biowaste-derived substances isolated from green compost (BBS-GC) are environmentally friendly reactants similar to humic substances, which contain multiple functionalities, that are suitable for adsorbing different kinds of pollutants in wastewater. Herein, sodium alginate (derived from brown algae) cross-linked with both Ca2+ ions and BBS-GC in the form of hydrogels and dried films are proposed as green, easy-to-form, and handleable materials for tertiary water treatments. The results show that both hydrogels and films are mechanically stable and can effectively remove differently charged dyes through an adsorption mechanism that can be described by the Freundlich model. BBS-GC-containing gels always performed better than samples prepared without BBS-GC, revealing that such unconventional materials can integrate waste valorization and water decontamination, potentially providing social and environmental benefits.

Enzyme-Functionalized Cellulose Beads as a Promising Antimicrobial Material

The extensive use of antibiotics over the last decades is responsible for the emergence of multidrug-resistant (MDR) microorganisms that are challenging health care systems worldwide. The use of alternative antimicrobial materials could mitigate the selection of new MDR strains by reducing antibiotic overuse. This paper describes the design of enzyme-based antimicrobial cellulose beads containing a covalently coupled glucose oxidase from Aspergillus niger (GOx) able to release antimicrobial concentrations of hydrogen peroxide (H₂O₂) (≈ 1.8 mM). The material preparation was optimized to obtain the best performance in terms of mechanical resistance, shelf life, and H₂O₂ production. As a proof of concept, agar inhibition halo assays (Kirby-Bauer test) against model pathogens were performed. The two most relevant factors affecting the bead functionalization process were the degree of oxidation and the pH used for the enzyme binding process. Slightly acidic conditions during the functionalization process (pH 6) showed the best results for the GOx/cellulose system. The functionalized beads inhibited the growth of all the microorganisms assayed, confirming the release of sufficient antimicrobial levels of H₂O₂. The maximum inhibition efficiency was exhibited toward Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli), although significant inhibitory effects toward methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus were also observed. These enzyme-functionalized cellulose beads represent an inexpensive, sustainable, and biocompatible antimicrobial material with potential use in many applications, including the manufacturing of biomedical products and additives for food preservation.

Development of an electrochemical sensor based on a cobalt oxide/tin oxide composite for determination of antibiotic drug ornidazole

A schematic illustration of the electrochemical performance towards sensing of ODZ at the Co₃O₄/SnO₂/GCE.