A systematic review on carbohydrate biopolymers for adsorptive remediation of copper ions from aqueous environments-part A: Classification and modification strategies

Characterization of polyphenols and carbohydrates exuded by Phaeodactylum tricornutum diatom grown under Cu stress

This study is focused on analysing polyphenols and carbohydrates released by Phaeodactylum tricornutum (P. tricornutum) diatoms cultured in natural seawater enriched with sublethal and lethal Cu doses. Cu concentrations of 0.31, 0.79 and 1.57 µM reduced cell densities by 37, 82 and 91%, respectively, compared to the control. The total sum of all identified polyphenols and total carbohydrates released by cells grown under lethal Cu levels increased up to 18.8 and 107.4 times, respectively, compared to data from a control experiment. Four different in vitro assays were used to estimate the antioxidant activities of the extracellular compounds: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition, cupric ion reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power and Cu complexing ability (CCA). The highest antioxidant activities were observed in the Cu lethal treatments, where the CCA assay exhibited a greater increase (up to 32.2 times higher than that found in the control experiment) to reduce the concentration of free Cu in the medium and its toxicity. The presence of Cu stimulated the release of polyphenols and carbohydrates to the medium as a detoxification mechanism to survive under lethal levels of Cu regulating its speciation.

Improved solar-driven water purification using an eco-friendly and cost-effective aerogel-based interfacial evaporator with exceptional photocatalytic capabilities

As a promising solution to address the global challenge of freshwater scarcity, solar-powered interfacial steam generation has undergone notable advancements. This study introduces a novel solar-driven interfacial evaporation membrane (ZnIn2S4@SiO2/ACSA, ZSAS) comprising a ZnIn2S4@SiO2 composite and a black sodium alginate aerogel infused with activated carbon. The ZSAS membrane demonstrates exceptional light absorption and thermal insulation, leading to elevated surface temperatures and reduced heat dissipation into the bulk water. Furthermore, the incorporation of AC reinforces the mechanical properties of the ZSAS membrane and enhances the water purification performance. These collective features result in an impressive evaporation rate of 1.485 kg m-2 h-1 and a high photothermal conversion efficiency of 91.2% under 1 sun irradiation for the optimal ZSAS membrane. Moreover, the optimal ZSAS membrane can effectively remove salts, heavy metal ions, and organic pollutants, benefitting from its superior evaporation separation effect and the photocatalytic properties of the ZnIn2S4@SiO2 composite.

Biopolymeric Nanocomposites for Wastewater Remediation: An Overview on Recent Progress and Challenges

Essential for human development, water is increasingly polluted by diverse anthropogenic activities, containing contaminants like organic dyes, acids, antibiotics, inorganic salts, and heavy metals. Conventional methods fall short, prompting the exploration of advanced, cost-effective remediation. Recent research focuses on sustainable adsorption, with nano-modifications enhancing adsorbent efficacy against persistent waterborne pollutants. This review delves into recent advancements (2020-2023) in sustainable biopolymeric nanocomposites, spotlighting the applications of biopolymers like chitosan in wastewater remediation, particularly as adsorbents and filtration membranes along with their mechanism. The advantages and drawbacks of various biopolymers have also been discussed along with their modification in synthesizing biopolymeric nanocomposites by combining the benefits of biodegradable polymers and nanomaterials for enhanced physiochemical and mechanical properties for their application in wastewater treatment. The important functions of biopolymeric nanocomposites by adsorbing, removing, and selectively targeting contaminants, contributing to the purification and sustainable management of water resources, have also been elaborated on. Furthermore, it outlines the reusability and current challenges for the further exploration of biopolymers in this burgeoning field for environmental applications.

Rapid and effective removal of copper, nitrate and trichloromethane from aqueous media by aluminium alloys

Zero-valent iron (ZVI) has been extensively studied for its efficacy in removing heavy metals, nitrate, and chlorinated organic compounds from contaminated water. However, its limited effectiveness due to rapid passivation and poor selectivity is prompting for alternative solutions, such as the use of aluminium alloys. In this study, the efficacy of five distinct aluminium alloys, namely Al-Mg, Al-Fe, Al-Cu, and Al-Ni, each comprising 50 % Al by mass at a concentration of 10 g/L, was assessed using copper, nitrate and trichloromethane (TCM) as model contaminants. Results show that chemical pollutants reacted immediately with Al-Mg. On the contrary, the remaining three alloys exhibited a delay of 24 h before demonstrating significant reactivity. Remarkably, Al-Mg alloy reduced nitrate exclusively to ammonium, indicating minimal preference for nitrate reduction to N2. In contrast, the Al-Cu, Al-Ni, and Al-Fe alloys exhibited N2 selectivity of 3 %, 5 %, and 19 %, respectively. The removal efficiency of copper, nitrate and TCM reached 99 % within 24 h, 95 % within 48h and 48 % within 48h, respectively. Noteworthy findings included the correlation between Fe concentration within the Al-Fe alloy and an increased N2 selectivity from 9.3 % to 24.1 %. This resulted in an increase of Fe concentration from 10 % to 58 % albeit with a concurrent reduction in reactivity. Cu2+ removal by Al-Fe alloy occurred via direct electron transfer, while the removal of nitrate and TCM was facilitated by atomic hydrogen generated by the alloy's hydrolysis. Intriguingly, nitrate and TCM suppressed Cu2+ reduction, whereas Cu2+ improved nitrate reduction and TCM degradation. These findings demonstrate the great potential of Al-Mg and Al-Fe alloys as highly efficient agents for water remediation.

Application of Cu isotopes to identify Cu sources in soils impacted by multiple anthropogenic activities

Copper (Cu) is an important micronutrient for animals and plants, but it is toxic at high concentrations in soil. Soils adjacent to industrial areas would be subjected to severe Cu pollution. Identifying Cu sources in the surface environment is crucial for understanding their pollution level and fate. This study investigated Cu content, isotope composition of topsoils, and two soil profiles with varying levels of Cu contamination and related potential Cu sources in southwest China. The difference in Cu isotope compositions of tailing (1.29 ± 0.08 ‰), smelting fly ash (0.04 ± 0.03 ‰), coal (2.44 ± 0.09 ‰), coal-burning fly ash (0.34 ± 0.03 ‰), and geogenic soil (0.10 ± 0.03 ‰) enabled us to distinguish anthropogenic Cu from geogenic Cu. The plot of δ65Cu and 1/Cu demonstrates that Cu of the polluted soils was from three end-members: the smelting fly ash, the vehicle exhaust, and the background soils. Based on the mass balance model, we calculated that the fly ash from smelting was the major anthropogenic source, contributing approximately 29 % of Cu contamination in soils, and the diesel exhaust was another important source, with a contribution rate of approximately 25 %. Additionally, soil profile results suggest that anthropogenic Cu could transport through soil profiles and influence Cu content and isotope signatures of subsurface soils, at least to a depth of ∼60 cm. Finally, our research indicates that Cu isotopes could be a promising tool for tracing industrial pollution, as significant Cu isotope fractionation would occur during the smelting process. Our research highlights the contribution of smelting and diesel exhaust to Cu contamination in the soils in a representative mining area. These findings serve as a scientific foundation for the development of policy for pollution control in industrial-affected regions.

Gelatin/poly(vinyl alcohol)-based dual functional composite films integrated with metal-organic frameworks and anthocyanin for active and intelligent food packaging

Innovative active and pH-colorimetric composite films were fabricated from gelatin/poly(vinyl alcohol) (Gel/PVA) integrated with copper-based metal-organic frameworks (Cu-MOFs) and red cabbage anthocyanin (RCA). The incorporation of Cu-MOFs improved the tensile strength, water resistance, and UV shielding properties of the developed composite films. The addition of anthocyanins and 3 wt% Cu-MOFs endowed the polymer matrix with excellent antioxidant (100 % against ABTS and DPPH radicals) and antibacterial (against Gram-positive and Gram-negative foodborne pathogenic bacteria) functions. The fabricated composite films exhibited significant color change at alkaline conditions of pH 7-12 and a marked color change upon exposure to ammonia. The designed indicator films used for shrimp freshness tracking and a visual color change from pink (for fresh shrimp) to green (for spoiled shrimp) was observed during storage at 28 °C for 24 h. The potential applications of the engineered composite films were studied by shrimp packaging, and the quality parameters of packaged samples were monitored during storage. The synergistic effects of adding anthocyanins and MOF nanostructures works for better product freshness preservation and responds well to shrimp spoilage level, introducing novel active and intelligent packaging options for practical smart packaging applications.

State-of-the-art advances in nanocomposite and bio-nanocomposite polymeric materials: A comprehensive review

The modern eco-friendly materials used in research and innovation today consist of nanocomposites and bio-nanocomposite polymers. Their unique composite properties make them suitable for various industrial, medicinal, and energy applications. Bio-nanocomposite polymers are made of biopolymer matrices that have nanofillers dispersed throughout them. There are several types of fillers that can be added to polymers to enhance their quality, such as cellulose-based fillers, clay nanomaterials, carbon black, talc, carbon quantum dots, and many others. Biopolymer-based nanocomposites are considered a superior alternative to traditional materials as they reduce reliance on fossil fuels and promote the use of renewable resources. This review covers the current state-of-the-art in nanocomposite and bio-nanocomposite materials, focusing on ways to improve their features and the various applications they can be used for. The review article also investigates the utilization of diverse nanocomposites as a viable approach for developing bio-nanocomposites. It delves into the underlying principles that govern the synthesis of these materials and explores their prospective applications in the biomedical field, food packaging, sensing (Immunosensors), and energy storage devices. Lastly, the review discusses the future outlook and current challenges of these materials, with a focus on sustainability.

Efficiency and mechanism in preparation and heavy metal cation/anion adsorption of amphoteric adsorbents modified from various plant straws

Cellulose can be modified for the loading of functional groups such as amino groups, sulfydryl groups, and carboxyl groups. Cellulose-modified adsorbents generally have specific adsorption capacities for either heavy metal anions or cations, and possess the advantages of wide raw material source, high modification efficiency, high adsorbent recyclability, and great convenience in recovery of the adsorbed heavy metals. At present, preparation of amphoteric heavy metal adsorbents from lignocellulose has attracted great attention. However, the difference in efficiency of preparing heavy metal adsorbents by modification of various plant straw materials and mechanism for the difference remain to be further explored. In this study, three plant straws, including Eichhornia crassipes (EC), sugarcane bagasse (SB) and metasequoia sawdust (MS), were sequentially modified by tetraethylene-pentamine (TEPA) and biscarboxymethyl trithiocarbonate (BCTTC) to obtain amphoteric cellulosic adsorbents (EC-TB, SB-TB and MS-TB, respectively), which can simultaneously adsorb heavy metal cations or anions. The heavy metal adsorption properties and mechanism before and after modification were compared. Pb(II) and Cr(VI) removal rates by the three adsorbents were 2.2-4.3 folds and 3.0-13.0 folds of those before modification, respectively, following the order of MS-TB > EC-TB > SB-TB. In the five-cycle adsorption-regeneration test, the Pb(II) and Cr(VI) removal rate by MS-TB decreased by 58.1 % and 21.5 %, respectively. Among the three plant straws, MS possessed the most abundant hydroxyl groups and the largest specific surface area (SSA), and accordingly MS-TB had the highest load of adsorption functional groups [(C)NH, (S)CS and (HO)CO] and also the largest SSA among the three adsorbents, which contribute to its highest modification and adsorption efficiency. This study is of great significance for screening suitable raw plant materials to prepare amphoteric heavy metal adsorbents with superior adsorption performance.

Research Progress and Trends on Utilization of Lignocellulosic Residues as Supports for Enzyme Immobilization via Advanced Bibliometric Analysis

Lignocellulosic biomasses are used in several applications, such as energy production, materials, and biofuels. These applications result in increased consumption and waste generation of these materials. However, alternative uses are being developed to solve the problem of waste generated in the industry. Thus, research is carried out to ensure the use of these biomasses as enzymatic support. These surveys can be accompanied using the advanced bibliometric analysis tool that can help determine the biomasses used and other perspectives on the subject. With this, the present work aims to carry out an advanced bibliometric analysis approaching the main studies related to the use of lignocellulosic biomass as an enzymatic support. This study will be carried out by highlighting the main countries/regions that carry out productions, research areas that involve the theme, and future trends in these areas. It was observed that there is a cooperation between China, USA, and India, where China holds 28.07% of publications in this area, being the country with the greatest impact in the area. Finally, it is possible to define that the use of these new supports is a trend in the field of biotechnology.

Preparation of cellulose-based porous adsorption materials derived from corn straw for wastewater purification

Various methods have been used to cope with heavy metal ion contamination in wastewater, which caused serious hazards to ecological and human health. Adsorption is one of the most frequent, economical and effective methods for removing these contaminants. Herein, a porous and amino-rich cellulose-based composite adsorbent (PEI-PCS) with anisotropic property was successfully prepared by covalently cross-linking polyethyleneimine on delignified corn straw. Combined with the porosity of straw substrate and the chelating ability of amino group to metal ions, the as-prepared PEI-PCS exhibited universality (various metal ions), rapid adsorption behavior (within 180 min achieve adsorption equilibrium), high adsorption capacity (85.47 mg g^-1 for Cu(II)), and good durability (70 % of adsorption efficiency after 5 cycles). In addition, the adsorption process was conformed to pseudo-second-order dynamics and the Langmuir isotherm models. Lastly, the adsorption mechanism was also elucidated. This study provides a sustainable pathway for the manufacture of efficient biomass-based adsorbents and confirms that functionalized corn straw is a promising material for the treatment of heavy metal ions.

Inhibition of humic acid on copper pollution caused by chalcopyrite biooxidation

Humic acid has the advantages of wide source, easy availability and environmental friendliness, which may be a good choice for inhibiting chalcopyrite biooxidation and alleviating copper pollution. However, there are few researches on the inhibitory effect and mechanism of humic acid on the biooxidation of chalcopyrite. In order to fill this knowledge gap, this study proposed and validated a novel method for inhibiting chalcopyrite biooxidation by means of humic acid. The results showed that the biooxidation of chalcopyrite could be effectively inhibited by humic acid, which consequently decreased the release of copper ions. Humic acid with a concentration of 120 ppm had the best inhibitory effect, which reduced the biooxidation efficiency of chalcopyrite from 40.7 ± 0.5 % to 29.3 ± 0.8 %. This in turn suggested that humic acid could effectively suppress the pollution of copper under these conditions. The analysis results of solution parameters, mineral surface morphology, mineral phases and element composition showed that humic acid inhibited the growth of Acidithiobacillus ferrooxidans, promoted the formation of jarosite and intensified the passivation of chalcopyrite, which effectively hindered the biooxidation of chalcopyrite, and would help to alleviate the pollution of copper.

Review on biopolymers and composites - Evolving material as adsorbents in removal of environmental pollutants

The presence of pollutants and toxic contaminants in water sources makes it unfit to run through. Though various conventional techniques are on deck, development of new technologies are vital for wastewater treatment and recycling. Polymers have been intensively utilized recently in many industries owing to their unique characteristics. Biopolymers resembles natural alternative to synthetic polymers that can be prepared by linking the monomeric units covalently. Despite the obvious advantages of biopolymers, few reviews have been conducted. This review focuses on biopolymers and composites as suitable adsorbent material for removing pollutants present in environment. The classification of biopolymers and their composites based on the sources, methods of preparation and their potential applications are discussed in detail. Biopolymers have the potentiality of substituting conventional adsorbents due to its unique characteristics. Biopolymer based membranes and effective methods of utilization of biopolymers as suitable adsorbent materials are also briefly elaborated. The mechanism of biopolymers and their membrane-based adsorption has been briefly reviewed. In addition, the methods of regeneration and reuse of used biopolymer based adsorbents are highlighted. The comprehensive content on fate of biopolymer after adsorption is given in brief. Finally, this review concludes the future investigations in recent trends in application of biopolymer in various fields in view of eco-friendly and economic perspectives.

Enhanced adsorption of copper ions from aqueous solution by two-step DTPA-modified magnetic cellulose hydrogel beads

Copper contamination of water is one of the most pressing environmental problems which has attracted extensive concern in recent decades. In this study, a series of magnetic adsorbents were synthesized by two-step modified cellulose with N-[3-(trimethoxysilyl)propyl]ethylenediamine (KH-792) and diethylenetriaminepentaacetic acid (DTPA) using for removal of Cu(II) from aqueous solutions. Adsorption performance of Cu(II) was systematically investigated under various treatment conditions as the effect of solution pH, contact time, initial concentration and temperature. The adsorption process was found to match better with the pseudo-second-order kinetics model, and the equilibrium adsorption data were well described by Langmuir model, which meant predominant governance of monolayer chemical adsorption. The analysis of FTIR and XPS confirmed the possible adsorption mechanism between Cu(II) and the synthesized adsorbents was electrostatic attraction and the chemical coordination. Compared with MCCs and APMC, DPMC showed higher adsorption capacity of Cu(II), reaching maximum adsorption capacity of 298.62 mg·g^-1 at pH 6. Given this, ease of preparation, low cost and excellent reusability, DPMC will be promising adsorbent for application in Cu(II) removal from wastewater.

Chemical Modification of Chitosan for Developing Cancer Nanotheranostics

Cancer is a worldwide public health issue that has not been conquered. Theranostics, the combination of a therapeutic drug and imaging agent in one formulation using nanomaterials, has been developed to better cure cancer in recent years. Although diverse biomaterials have been applied in cancer theranostics, chitosan (CS), a natural polysaccharide bearing easy modification sites with excellent biocompatibility and biodegradability, shows great potential for developing cancer nanotheranostics. In this review, we seek to describe the chemical functionalities of CS used in cancer theranostics and their synthesis methods. We also present recent discoveries and research progresses on how the CS functionalization could improve the delivery efficiency of CS-based nanotheranostics. Finally, we report several case studies about the application of CS-based nanotheranostics. This paper focuses on the strategies to construct CS-based theranostics systems via chemical routes and highlights their applications in cancer treatment, which can provide useful references for further studies.

Influence of Surface Pretreatments on the Anticorrosion of Polypyrrole Electro-Polymerized Coatings for Copper in Artificial Seawater

Plasma discharging treatment (hydroxylation) was conducted on copper surfaces for the subsequent electro-polymerization procedure of polypyrrole (PPy) coating (d-PPy). The hydroxylated surface could solve the criticized adhesion strength and protection efficiency of electropolymerized coatings for metal substrate in corrosive media. Compared with the counterpart obtained via passivation pretreatment (p-PPy), a well-adhered d-PPy layer was acquired on the hydroxylated copper surface, which earned a satisfactory adhesion grade, compactness and conductivity. Appreciable protection of d-PPy was measured for copper in the artificial seawater (ASW) at 298 K via electrochemical and surface analyses. Results of electrochemical measurements indicated that d-PPy coating effectively retarded copper corrosion in ASW with a lowered corrosion current density and improved charge transfer resistance. Surface analysis revealed that the typical morphology of PPy was retained after 240 h immersion in ASW. A favorable physical barrier and anodic protection efficacy might account for the superior protection of d-PPy coating for the underlying copper. Molecular dynamics simulations for the deposition of PPy chains on pristine and hydroxylated copper planes provided a definite correlation between the theoretical calculations and experimental observations. Theoretical modelling also disclosed in-depth the anchoring nature and anticorrosive mechanism for PPy toward the hydroxylated copper in ASW.

Preparation and characterization of graphitic carbon nitrides/polyvinylidene fluoride adsorptive membrane modified with chitosan for Rhodamine B dye removal from water: Adsorption isotherms, kinetics and thermodynamics

In the present study, a PVDF/g-C₃N₄/chitosan (PCC) membrane was used for the removal of Rhodamine B from aqueous solutions. Water flux for PCC membrane decreased from 49.87% to 14.76% by the addition of chitosan from 2% to 4%. Afterward, batch adsorption conditions were optimized for a PVDF/g-C₃N₄/chitosan membrane applying Box-Behnken design algorithm. The maximum RB removal efficiency was 72.74% at 2 mg/L of initial RB concentration, pH = 3, 2 g of g-C₃N₄ and 3% of chitosan at the optimum conditions. The Freundlich isotherm and pseudo-second order models were satisfactorily describing the equilibrium and kinetic of adsorption, respectively. Thermodynamic parameters were disclosed that the adsorption of RB onto PCC was exothermic (ΔH° = -21.35 kJ mol^-1) and spontaneous (ΔG° < 0) with the generation of energy (ΔS° = +92.42 kJ mol^-1) at the interface of solid/liquid. Thus, this novel membrane could be employed as an effective adsorbent to remove of RB dye from aqueous solutions.

Chitosan films and scaffolds for regenerative medicine applications: A review

Over the last years, chitosan has demonstrated unparalleled characteristics for regenerative medicine applications. Beside excellent antimicrobial and wound healing properties, this polysaccharide biopolymer offers favorable characteristics such as biocompatibility, biodegradability, and film and fiber-forming capabilities. Having plentiful active amine groups, chitosan can be also readily modified to provide auxiliary features for growing demands in regenerative medicine, which is constantly confronted with new problems, necessitating the creation of biocompatible, immunogenic and biodegradable film/scaffold composites. A new look at the chitosan composites structure/activity/application tradeoff is the primary focus of the current review, which can help researchers to detect the bottlenecks and overcome the shortcomings that arose from this intersection. In the current review, the most recent advances in chitosan films and scaffolds in terms of preparation techniques and modifying methods for improving their functional properties, in three major biomedical fields i.e., tissue engineering, wound healing, and drug delivery are surveyed and discussed.

Computational study of the interaction of heavy metal ions, Cd(II), Hg(II), and Pb(II) on lignin matrices

Contamination by heavy metal ions, particularly in water resources, is a severe environmental problem. In this study, the interaction of metal ions, namely, Cadmium Cd(II), Mercury Hg(II), and Lead Pb(II), on lignin matrices was investigated based on theoretical calculations. Binding energy (ΔE_Bind) values proved that the Pb(II) interacted better with lignin matrices than Cd(II) or Hg(II), having energy values between -8.4 kcal mol^-1 to -20.2 kcal mol^-1. The Gibbs energy (ΔG) and enthalpy (ΔH) values for Pb(II) were <0, indicating that the process was spontaneous and released heat. However, the lignin matrices studied in this work did not interact efficiently with Cd(II) and Hg(II) ions because almost all ΔE_Bind, ΔG, and ΔH values were positive. The bond length of the interaction proved that the Pb ions yielded the smallest values, ratifying the values for the interaction energy. Analyses based on the quantum theory of atoms in molecules showed that the interactions between Pb(II) and the matrices were partially covalent, whereas the interactions of Cd(II) and Hg(II) were predominantly electrostatic, justifying the positive values of ΔE_Bind, ΔG, and ΔH. The natural bond orbital results showed that the ligand orbitals of the matrix interacted with the lone pair antibonding orbital (LP*) of the metal ions. The theoretical results of the study show the possibility of applying lignin to remove heavy metal ions, especially Pb, and providing information for research related to wastewater treatment.

Current Status and Future Perspectives of Supports and Protocols for Enzyme Immobilization

The market for industrial enzymes has witnessed constant growth, which is currently around 7% a year, projected to reach $10.5 billion in 2024. Lipases are hydrolase enzymes naturally responsible for triglyceride hydrolysis. They are the most expansively used industrial biocatalysts, with wide application in a broad range of industries. However, these biocatalytic processes are usually limited by the low stability of the enzyme, the half-life time, and the processes required to solve these problems are complex and lack application feasibility at the industrial scale. Emerging technologies create new materials for enzyme carriers and sophisticate the well-known immobilization principles to produce more robust, eco-friendlier, and cheaper biocatalysts. Therefore, this review discusses the trending studies and industrial applications of the materials and protocols for lipase immobilization, analyzing their advantages and disadvantages. Finally, it summarizes the current challenges and potential alternatives for lipases at the industrial level.

A Simple One-Step Modification of Shrimp Shell for the Efficient Adsorption and Desorption of Copper Ions

Removing toxic heavy metal species from aqueous solutions is a point of concern in our society. In this paper, a promising biomass adsorbent, the modified waste shrimp shell (MS), for Cu (II) removal was successfully prepared using a facile and simple one-step modification, making it possible to achieve high-efficiency recycling of the waste NaOH solution as the modification agent. The outcome shows that with the continuous increase in pH, temperature and ion concentration, the adsorption effect of MS on Cu (II) can also be continuously improved. Adsorption isotherm and adsorption kinetics were fitted with the Langmuir isotherm model and the pseudo-second-order model, respectively, and the maximum adsorption capacity of Cu (II) as obtained from the Langmuir isotherm model fitting reached 1.04 mmol/g. The systematic desorption results indicated that the desorption rate of Cu (II) in the MS could reach 100% within 6 min, where HNO3 is used as the desorption agent. Moreover, experiments have proven that after five successive recycles of NaOH as a modifier, the adsorption capacity of MS on Cu (II) was efficient and stable, maintaining tendency in 0.83-0.85 mmol/g, which shows that waste NaOH solution can be used as a modification agent in the preparation of waste shrimp shell adsorbent, such as waste NaOH solution produced in industrial production, thereby making it possible to turn waste into renewable resources and providing a new way to recycle resources.

A State-of-the-Art Review on Biowaste Derived Chitosan Biomaterials for Biosorption of Organic Dyes: Parameter Studies, Kinetics, Isotherms and Thermodynamics

Chitosan is a second-most abundant biopolymer on earth after cellulose. Its unique properties have recently received particular attention from researchers to be used as a potential biosorbent for the removal of organic dyes. However, pure chitosan has some limitations that exhibit lower biosorption capacity, surface area and thermal stability than chitosan composites. The reinforcement materials used for the synthesis of chitosan composites were carbon-based materials, metal oxides and other biopolymers. This paper reviews the effects of several factors such as pH, biosorbent dosage, initial dye concentration, contact time and temperature when utilizing chitosan-based materials as biosorbent for removing of organic dyes from contaminated water. The behaviour of the biosorption process for various chitosan composites was compared and analysed through the kinetic models, isotherm models and thermodynamic parameters. The findings revealed that pseudo-second-order (PSO) and Langmuir isotherm models were best suited for describing most of the biosorption processes or organic dyes. This indicated that monolayer chemisorption of organic dyes occurred on the surface of chitosan composites. Most of the biosorption processes were endothermic, feasible and spontaneous at the low temperature range between 288 K and 320 K. Therefore, chitosan composites were proven to be a promising biosorbent for the removal of organic dyes.

Recent advances in the polyurethane-based adsorbents for the decontamination of hazardous wastewater pollutants

The pollution of aquatic systems with noxious organic and inorganic contaminants is a challenging problem faced by most countries. Water bodies are contaminated with diverse inorganic and organic pollutants originating from various diffuse and point sources, including industrial sectors, agricultural practices, and domestic wastes. Such hazardous water pollutants tend to accumulate in the environmental media including living organisms, thereby posing significant environmental health risks. Therefore, the remediation of wastewater pollutants is a priority. Adsorption is considered as the most efficient technique for the removal of pollutants in aqueous systems, and the deployment of suitable adsorbents plays a vital role for the sustainable application of the technique. The present review gives an overview of polyurethane foam (PUF) as an adsorbent, the synthesis approaches of polyurethane, and characterization aspects. Further emphasis is on the preparation of the various forms of polyurethane adsorbents, and their potential application in the removal of various challenging water pollutants. The removal mechanisms, including adsorption kinetics, isotherms, thermodynamics, and electrostatic and hydrophobic interactions between polyurethane adsorbents and pollutants are discussed. In addition, regeneration, recycling and disposal of spent polyurethane adsorbents are reported. Finally, key knowledge gaps on synthesis, characterization, industrial applications, life cycle analysis, and potential health risks of polyurethane adsorbents are discussed.

Kinetic, Thermodynamic, Physicochemical, and Economical Characterization of Pectin from Mangifera indica L. cv. Haden Residues

The effect of temperature (60, 70, 80, and 90 °C) and time (30, 45, 60, 75, and 90 min) on citric acid extraction of Haden mango (Mangifera indica L. cv. Haden) peel pectin was evaluated in the present study. In order to obtain a better understanding of both the extraction process and the characteristics of the pectin (obtained from an agro-industrial waste) for a future scaling process, the following characterizations were performed: (1) Kinetic, with the maximum extraction times and yields at all evaluated temperatures; (2) thermodynamic, obtaining activation energies, enthalpies, entropies, and Gibbs free energies for each stage of the process; (3) physicochemical (chemical analysis, monosaccharide composition, degree of esterification, galacturonic acid content, free acidity, Fourier-transform infrared spectroscopy, thermogravimetric and derivative thermogravimetric analyses); and (4) economical, of the pectin with the highest yield. The Haden mango peel pectin was found to be characterized by a high-esterified degree (81.81 ± 0.00%), regular galacturonic acid content (71.57 ± 1.26%), low protein (0.83 ± 0.05%) and high ash (3.53 ± 0.02%) content, low mean viscometric molecular weight (55.91 kDa), and high equivalent weight (3657.55 ± 8.41), which makes it potentially useful for food applications.

Interaction of glyphosate in matrices of cellulose and diethylaminoethyl cellulose biopolymers: theoretical viewpoint of the adsorption process

Glyphosate is an herbicide widely used in agricultural activities causing contamination of soils and bodies of water and damage to the biodiversity of ecosystems. In this context, the present study aimed to theoretically study the adsorption potential of the biopolymer cellulose (CE) and its diethylaminoethyl cellulose derivative (DEAEC) with the herbicide glyphosate (GLY). Theoretical calculations were performed using the density functional theory. Molecular electrostatic potential and frontier molecular orbital analyses were performed, which allowed identifying the possible sites of interaction of biopolymers that were in the functional groups -OH and O- of cellulose and in the groups -O- and -NH+(CH2CH3)2 of the DEAEC. Reactivity indices chemical softness and hardness showed that both adsorbents could interact with adsorbate. Simulated IR indicated that the interactions could be evinced in experimental measurements by changes in the bands of glyphosate (ν(P = O), δ(P-O-H), δ(C-N-H)) or in the bands of CE and DEAEC (ν(C-O), ν(C-H), ν(N-H)). The binding energies showed that the GLY interacts more effectively with CE than DEAEC. The ΔH prove that all processes are exothermic and the CE-GLY1 interaction showed value of ΔG < 0. The topological results showed a greater number of interactions with electrostatic nature. The results found in the study show that the theoretical data provides useful information to support the use of biopolymers as matrices for glyphosate adsorption or other contaminants.

The Characterization of Scaffolds Based on Dialdehyde Chitosan/Hyaluronic Acid

In this work, two-component dialdehyde chitosan/hyaluronic acid scaffolds were developed and characterized. Dialdehyde chitosan was obtained by one-step synthesis with chitosan and sodium periodate. Three-dimensional scaffolds were prepared by the lyophilization method. Fourier transform infrared spectroscopy (FTIR) was used to observe the chemical structure of scaffolds and scanning electron microscopy (SEM) imaging was done to assess the microstructure of resultant materials. Thermal analysis, mechanical properties measurements, density, porosity and water content measurements were used to characterize physicochemical properties of dialdehyde chitosan/hyaluronic acid 3D materials. Additionally, human epidermal keratinocytes (NHEK), dermal fibroblasts (NHDF) and human melanoma cells (A375 and G-361) were used to evaluate cell viability in the presence of subjected scaffolds. It was found that scaffolds were characterized by a porous structure with interconnected pores. The scaffold composition has an influence on physicochemical properties, such as mechanical strength, thermal resistance, porosity and water content. There were no significant differences between cell viability proliferation of all scaffolds, and this observation was visible for all subjected cell lines.

Novel Adsorbent Based on Banana Peel Waste for Removal of Heavy Metal Ions from Synthetic Solutions

Due to its valuable compounds, food waste has been gaining attention in different applications, such as life quality and environment. Combined with circular economy requirements, a valorization method for waste, especially banana waste, was to convert them into adsorbents with advanced properties. The banana waste, after thermal treatment, was used with high removal performances (100%) for the removal of heavy metals, such as Cr, Cu, Pb, and Zn, but their small particle size makes them very hard to recover and reuse. For this reason, a biopolymeric matrix was used to incorporate the banana waste. The matrix was chosen for its remarkable properties, such as low cost, biodegradability, low carbon footprint, and reduced environmental impact. In this research, different types of materials (simple banana peel ash BPA and combined with biopolymeric matrix, ALG–BPA, CS–BPA) were prepared, characterized, and tested. The materials were characterized by means of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), optical microscopy (OM), scanning electron microscopy (SEM), and tested for the removal of metal ions from synthetic solutions using atomic absorption spectroscopy (AAS). The ALG–BPA material proved to be the most efficient in the removal of heavy metal ions from synthetic solution, reaching even 100% metal removal for Cr, Fe, Pb, and Zn, while the CS-based materials were the least efficient, presenting the best values for Cr and Fe ions with a removal efficiency of 34.14% and 28.38%, respectively. By adding BPA to CS, the adsorption properties of the material were slightly improved, but also only for Cr and Fe ions, to 37.09% and 57.78%.

Quantum mechanical study on physisorption of dissolved metal ions in seawater using cellulose, chitosan and chitin

Density Functional Theory (DFT) calculations were performed to investigate the adsorption of alkali and alkaline earth metal ions, Na⁺, K⁺, Mg²⁺, and Ca²⁺ present in seawater by biopolymers, cellulose, chitosan, and chitin. Analysis of the optimized geometries of the complexes formed by physisorption of metal ions on biopolymers reveals that monomer of chitin is the best biopolymer for adsorption of Mg²⁺ ion. Water as a solvent reduces the reactivity of complexes formed, playing a significant role in complex stability, which further proved the effective use of cellulose, chitosan and chitin for real-time applications. Natural Bond Orbital (NBO) analysis and quantum reactivity descriptors of the optimized geometries indicate that the electronic charge transfer between the biopolymer and metal ions acts as a driving force for the complex formation. This study also highlights the significant role of water in physisorption of metal ions on biopolymer.

Glycogen nanoparticles as a potential corrosion inhibitor

Biological macromolecules are proven to be potential green corrosion inhibitors because of their outstanding structural features and eco-friendliness. This study is aimed at enhancing their corrosion mitigation capabilities by converting them into nanoparticles. This is the first work where nanoparticles of biological macromolecules are exploited for corrosion mitigation studies. Glycogen nanoparticles (GLY-Np) were synthesized by microwave-mediated nanoprecipitation method and characterized by ATR-FTIR, XRD, UV-Visible Spectroscopy, FESEM analysis, EDX, TEM, and Zeta potential measurements. They are used as an eco-friendly inhibitor for corrosion control of zinc in sulfamic acid (NH₂SO₃H). The electrochemical study was a primary experimental tool employed for corrosion rate measurement. Conditions were optimized to obtain maximum inhibition efficiency by varying concentrations of inhibitor and temperature. Activation and thermodynamic parameters were evaluated and discussed in detail. A suitable adsorption isotherm was proposed to fit the experimental results. Adsorption of the inhibitor was confirmed by SEM, EDX, and AFM techniques. The inhibition efficiency of 92% was obtained for 0.02 gL^-1 GLY-Np. Thus, GLY-Np turned out to be an effective green inhibition with economic benefits.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Multivariate data-based optimization of membrane adsorption process for wastewater treatment: Multi-layer perceptron adaptive neural network versus adaptive neural fuzzy inference system

Application of machine-learning methods to assess the batch adsorption of malachite green (MG) dye on chitosan/polyvinyl alcohol/zeolite imidazolate frameworks membrane adsorbents (CPZ) was investigated in this study. Our previous research results proved the suitability of the CPZ membranes for wastewater decoloring. In the current work, the residence time was combined with the other operational variables i.e., pH, initial dye concentration, and adsorbent dose (AD), to obtain the possible interactions involved in nonequilibrium adsorption. Two well-known soft-computing approaches, multi-layer perceptron adaptive neural network (MLP-ANN) and adaptive neural fuzzy inference system (ANFIS), were selected among different machine learning alternatives and then, comprehensively compared with each other considering reliability and accuracy for a 60 number of runs. The ANFIS structure with nine centers of clusters could predict the adsorption performance better than the ANN approach. Root mean square error (RMSE) and R-square were obtained 0.01822 and 0.9958 for the test data, respectively. The interpretability test resulted a linear trend predicted by the model and disclosed that the maximum value of the removal efficiency (99.5%) could be obtained when the amount of the inputs set to the upper limit. Lastly, the sensitivity analysis uncovered that the residence time has a decisive effect (relevancy factor > 80%) on the removal efficiency. According to the results, ANFIS is an effective and reliable tool to optimize and intensify the membrane adsorption process.

A systematic review on carbohydrate biopolymers for adsorptive remediation of copper ions from aqueous environments-Part B: Isotherms, thermokinetics and reusability

The presence of copper in aquatic environment is a serious threat for human health and ecosystem conservation. Adsorption is a powerful, operable and economic method for remediation of copper ions from aqueous phase. Carbohydrate biopolymers have emerged as promising, effective and environmental-friendly adsorbents for copper remediation. In part A of this review, different types of carbohydrate biopolymer adsorbents were surveyed focusing on prevalent and novel synthesis and modification methods. In current work (part B of the review), isothermal, thermodynamic and kinetic aspects of the copper adsorption by carbohydrate-based adsorbents as well as the regeneration and reusability of the biopolymer adsorbents are overviewed. Adsorption capacity, time required for equilibrium (adsorption rate), thermal-sensitivity of the adsorption, favorability extent, and sustainability of the adsorbents and adsorption processes are valuable and useful outcomes, resulted from the thermokinetic and reusability investigations. Such considerations are critical for the process design and scale up regarding technical, economical and sustainability of the adsorption process.