Facile synthesis of crosslinked chitosan-tripolyphosphate/kaolin clay composite for decolourization and COD reduction of remazol brilliant blue R dye: Optimization by using response surface methodology

Cellulose-citric acid-chitosan@metal sulfide nanocomposites: Methyl orange dye removal and antibacterial activity

In this study, to develop efficient adsorbents in removing water pollution, new cellulose-citric acid-chitosan@metal sulfide nanocomposites (CL-CA-CS@NiS and CL-CA-CS@CuS) were synthesized by one-pot reaction at mild conditions and characterized using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), Energy Dispersive X-ray (EDX) and Brunauer-Emmett-Teller (BET) isotherm. The results of characterization techniques confirm that the desired compounds have been successfully synthesized. The as-prepared composites were applied for the removal of methyl orange (MO) dye from aqueous solutions using a batch technique, and the effect of key factors such as initial pH, shaking time, MO concentration, temperature and adsorbent dose were investigated and discussed. Adsorption results exhibited positive impact of temperature, shaking time and adsorbent dose on the MO removal percent. The MO removal percent has been increased over a wide range of pH from 2 (27.6 %) to 6 (98.8 %). Also, almost being constant over a wide range of MO concentration (10-70 mg/L). The results demonstrated that the maximum removal percentage of MO dye (98.9 % and 93.4 % using CL-CA-CS@NiS and CL-CA-CS@CuS, respectively) was achieved under the conditions of pH 6, shaking time of 120 min, adsorbent dose of 0.02 g, MO concentration of 70 mg/L and temperature of 35 °C. The pseudo-second-order (PSO) and Langmuir models demonstrated the best fit to the kinetic and equilibrium data. Also, the thermodynamic results showed that the MO removal process is endothermic and spontaneous in nature. The MO adsorption can be happened by different electrostatic attraction, n-π and π-π stacking and also hydrogen bonding interaction. In addition, antibacterial activity of CL-CA-CS@NiS and CL-CA-CS@CuS nanocomposites exhibited a superior efficiency against S. aureus.

Investigation of adsorption potential of acid violet 90 dye with chitosan/halloysite/boron nitride composite materials

In this study, composite adsorbents consisting of a mixture of chitosan (CTS), boron nitride (h-BN) and halloysite (HNT) were used for the adsorption of Acid Violet 90 (AV90) dye in a batch system. Adsorbents CTS, CTS/HNT, CTS/h-BN and CTS/h-BN/HNT beads were prepared by simple dropping method and dried in a freeze dryer. The beads were characterized by FT-IR, SEM and zeta potential analysis. The effects of pH (2-8) and dye concentration (50-250 mg/L) on AV90 adsorption properties of beads were investigated. In addition, Langmuir, Freunlich, Temkin and Henry adsorption isotherm models were used to examine the dye adsorption mechanism. It was observed that the Langmuir and Freundlich adsorption isotherm models were in good agreement with the experimental data. In the dye concentration range studied, the qm values of CTS, CTS/h-BN1, CTS/h-BN3, CTS/HNT/h-BN1, CTS/HNT/h-BN3, CTS/HNT obtained from the Langmuir isotherm model was 27.62, 17.80, 10.11, 8.71, 32.57, 19.96 mg/g, respectively. Pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models were used to examine the adsorption kinetics of adsorbents. As a result, it is thought that the use of this study in the field of dye adsorption can be an innovative and important study.

A biohybrid nanomaterial of biosynthesized TiO2 NPs from Mangrove leaf and shrimp shell-based Chitosan: ultrasonic-assisted synthesis and its application for methylene blue removal and COD reduction of real industrial wastewater

In the present study, TiO2 NPs (particle size: 25-35 nm) were biosynthesized from the Mangrove leaf extract. These nanoparticles were used to modify chitosan, and Chitosan@TiO2 biohybrid nanomaterial was synthesized and characterized using FTIR, XRD, BET, and, EDX-FE-SEM analyses. The adsorption ability of Chitosan@TiO2 nanomaterial has been investigated for Methylene blue (MB) removal from aqueous solution. The results indicated that the amount of MB removal is high in alkaline pH (optimum pH = 9). The pseudo-second-order model was able to describe the effect of contact time on the adsorption ability. The Langmuir model well described the equilibrium manner, and one gram of Chitosan@TiO2 could attract 416.66 mg of MB. Kinetic data, values of parameters of activation energy (+57.283 kJ/mol), enthalpy (-86.8148 kJ/mol), and Gibbs free energy (-27.999 to -22.8987 kJ/mol) indicate the dominance of chemical adsorption over physical adsorption. The breakthrough curves of 3 adsorption/desorption cycles showed the acceptable ability and reusability of prepared nanomaterial. Synthesized biohybrid nanomaterial can reduce 75% COD and 79% nitrate of the effluent from industrial city no.3 of Yasouj. The results of this research show the high ability of chitosan@TiO2 biohybrid to remove dyes from wastewater and reduce the pollution load of industrial wastewater.

Chitosan anchored nZVI bionanocomposites for treatment of textile wastewater: Optimization, mechanism, and phytotoxic assessment

In recent years, there has been a growing focus on treating textile wastewater due to its escalating threat to aquatic ecosystems and exposed communities. The present study investigates the adsorption efficacy of biopolymer functionalized nanoscale zero-valent iron (CS@nZVI) composite for the treatment of textile wastewater using the RSM-CCD model. The structure and morphology of CS@nZVI were characterized using XRD, FTIR, FESEM, and EDX. CS@nZVI was then evaluated for its adsorption potential in removing COD, color, and other physico-chemical parameters from textile wastewater. The results showed the high efficacy of CS@nZVI for COD and color removal from textile wastewater. Under optimal conditions (pH 6, contact time 60 min, and 1.84 g CS@nZVI), COD removal reached a maximum of 85.53%, and decolorization efficiency was found to be 89.73%. The coefficient of determination R2 (0.98) and AIC (269.75) values suggested quadratic model as the best-fitted model for optimizing the process parameters for COD removal. Additionally, the physico-chemical parameters were found to be within permissible limits after treatment with CS@nZVI. The influence of coexisting ions on COD removal followed the order PO43- > SO42- > Cl- >Na+ > Ca2+. The kinetics data fitted well with the pseudo-first-order reaction, indicating physisorption as the primary mechanism. The thermodynamic study revealed the endothermic nature of the removal process. Reusability tests demonstrated that great regeneration capacity of spent CS@nZVIafter five consecutive cycles. Furthermore, toxicological studies showed reduced toxicity in treated samples, leading to improved growth of Vigna radiata L. These findings suggest that CS@nZVI bionanocomposites could serve as an efficient, cost-effective, and eco-friendly remediation agent for the treatment of textile effluents, presenting significant prospects for commercial applications.

Advances in the greener synthesis of chromopyrimidine derivatives by a multicomponent tandem oxidation process

A hydrophilic cobalt/copper heterogeneous bimetallic catalyst named mTEG-CS-Co/Cu-Schiff-base/IL was successfully synthesized from chitosan polysaccharide. The new catalyst was investigated and confirmed using various techniques including FT-IR, FE-SEM, EDX-EDS, XRD, TEM, TGA, AFM, NMR and ICP. The catalyst exhibited powerful catalyst activity for the tandem one pot oxidative chromopyrimidine reaction from benzyl alcohols under mild conditions, utilizing air as a clean source in a green protocol. The catalyst was compatible with a wide range of benzyl alcohols, and aldehydes formed in situ, and bis-aldehydes synthesized were condensed with urea/4‑hydroxycumarin to provide favorable products in good yields for all derivatives (14 new derivatives). The presence of tri-ethylene glycol and imidazolium moieties with hydrophilic properties on the mTEG-CS-Co/Cu-Schiff-base/IL nanohybrid provides dispersion of the nanohybrid particles in water, leading to higher catalytic performance. Furthermore, the reaction exhibited several other notable features, including low catalyst loading, the ability to be recycled for up to 6 stages, high atom economy, a simple work procedure, short reaction time, utilization of an environmentally friendly nanohybrid, and the replacement of volatile and organic solvents with water solvent.

"Adsorptive removal of Congo Red dye from its aqueous solution by Ag-Cu-CeO2 nanocomposites: Adsorption kinetics, isotherms, and thermodynamics"

Eliminating synthetic dyes and organic contaminants from water is crucial for safeguarding human health and preserving the environment. In this study, we explored the effectiveness of Ag-Cu-CeO2 nanocomposites as adsorbents to remove Congo Red dye from water. Three compositions of Ag-Cu-CeO2 nanocomposites (10:20:70, 15:15:70, and 20:10:70) have been synthesized by the aqueous coprecipitation method. A comprehensive analysis was performed by different techniques including X-ray diffraction, Fourier transform infrared spectroscopy, BET surface area determination, Thermogravimetric analysis, Scanning electron microscopy, and TEM. The synthesized nanocomposites have a dimension of 5 ± 1 nm and a high surface area (51.832-78.361 m2g-1). Among these, the nanocomposite with composition 15:15:70 showed the highest adsorption capacity of 4.71 mg/g adsorption (96.83 % removal) from the 0.8 × 10-4 M (55.6 mg/l) Congo Red solution at pH values of 2 at 20 °C with contact time of 3h. The adsorption data is best fitted in the Freundlich adsorption isotherm and pseudo-second-order kinetic model. The negative values of enthalpy variation (-27.57, -26.43, and -16.73 kJ/mol) demonstrated that the adsorption was spontaneous and exothermic. The cycling run showed a mere 12 % deactivation after five cycles of use thus indicating that Ag-Cu-CeO2 nanocomposites hold great potential as effective and eco-friendly adsorbents to remove Congo Red from water.

Olive mill wastewater treatment using natural adsorbents: phytotoxicity on durum wheat (Triticum turgidum L. var. durum) and white bean (Phaseolus vulgaris L.) seed germination

This research was undertaken to optimize the phenolic compound removal from Olive Mill Wastewater (OMW) by sawdust and red clay as natural adsorbents. Fractional factorial experimental design at 25-1 was used in order to optimize the experimental conditions for high removal efficiency. Statistics ANOVA analysis, Fisher's test, and Student's test suggested that the adsorbent dose has the most significant influence on polyphenol removal for both adsorbents. The maximum removal of polyphenols by sawdust reached 49.6% at 60 °C by using 60 g/L of adsorbent dose, pH 2, reaction time of 24 h, and agitation speed of 80 rpm. Whereas, for red clay, 48.08% of polyphenols removal was observed under the same conditions for sawdust except the temperature of 25 °C instead of 60 °C. In addition, the thermodynamic parameters suggested spontaneous process for both adsorbents, endothermic for the sawdust and exothermic for red clay. Furthermore, the phytotoxicity effect of OMW on durum wheat (Triticum turgidum L. var. durum) and white bean (Phaseolus vulgaris L.) seed germination was investigated. The obtained results showed that the untreated OMW inhibited the seed germination of T. turgidum and P. vulgaris seeds. OMW treatment with red clay followed by dilution (95% water) resulted in 87 and 30% germination of P. vulgaris and T. turgidum, respectively. While, the treatment of OMW with sawdust and dilution at 95% resulted in 51 and 26% germination of P. vulgaris and T. turgidum, respectively.

Cross-linked chitosan-epichlorohydrin/bentonite composite for reactive orange 16 dye removal: Experimental study and molecular dynamic simulation

Chitosan/bentonite beads (CsB) composites were prepared from chitosan (Cs) and bentonite (B) and cross-linked with epichlorohydrin for removal of reactive orange 16 (RO16) and methylene blue (MB). The adsorption results have shown that the (Cs20B80), 20 % wt of (Cs) and 80 % (B), was selected as the best adsorbent for (MB) and (RO16) dyes. SEM, EDX, FTIR, BET, and pHpzc were implemented to investigate the features of Cs, B, and Cs20B80 samples. The influence of contact time (0-72 h), initial RO16 concentration (15-300 mg/L), temperature (30, 40, and 50 °C), the quantity of adsorbent (1-4 g/L), ion strength (0.1-1 M), and solution pH (3-10) on RO16 adsorption onto Cs20B80 were explored. The pseudo-second-order and the Langmuir models fit adequately the adsorption kinetic results and the isotherms ones respectively. Also, the maximal monolayer capacities calculated using the non-linear form of the Langmuir isotherm are 55.27, 55.29, and 70.80 mg/g, at 30, 40 and 50 °C. Based to the statistical physics model, the RO16 could be retained on the surface of Cs20B80 through a non-parallel orientation. The RO16 adsorption process is endothermic and natural, as demonstrated by thermodynamic studies. After three regeneration cycles, the Cs20B80 composite has shown an adsorption capacity of around 20 % compared to the initial one. The adsorption energy of RO16 onto Cs, B, and Cs20B80 examined using the Monte Carlo simulation method (MC) ranged from -164.8 to -303.7 (kcal/mol), showing the potential of the three adsorbants for RO16 dye. Also, the process of adsorption of RO16 dye on the surface of Cs20B80 composite indicates several kinds of physical interactions, involving electrostatic interaction, hydrogen bonding, and π-π interactions, this finding was proved theoretically via molecular dynamic simulations.

Performance of hybrid biofilter based on rice husks/sawdust treating grey wastewater

An innovative nature-based technology for wastewater treatment is the hybrid biofiltration, which combines complex symbiotic relationships between plants, earthworms and microorganisms with adequate support components. This latter could be optimized using organic supports. The aim of this research was to evaluate the performance of hybrid biofilters based on rice husks/sawdust treating grey wastewater from mining camps. Four biofilters using an active layer (rice husks/sawdust: 50/50%, v/v) at 60(B₆₀) and 45(B₄₅) cm height and operating for 64 days at a hydraulic loading rate between 1 and 5 m³/m²d were monitored. Eisenia foetida Savigny and Cyperus papyrus L. were used as a biotic component. COD, N-NH₄⁺, NO₃^-, NO₂^-, PO₄^3- and fecal coliforms were weekly monitored. Results showed that the most efficient HB was using 60 cm as an active layer and operating at 3 m³/m²d, which reported average removal efficiencies for COD, NH₄⁺, NO₃^-, PO₄^3- and fecal coliforms up to 85, 89, 47, 49 and 99.9%, respectively. Organic support improved the rate growth for Cyperus papirus L. and E. foetida Savigny up to 50%. Hybrid biofiltration using organic residues is low-cost, providing all-encompassing operational and performance features, improving the wastewater reclamation opportunities.

A kaolin/calcium incorporated shape memory and antimicrobial chitosan-dextran based cryogel as an efficient haemostatic dressing for uncontrolled hemorrhagic wounds

Increased mortalities associated with uncontrolled and excessive bleeding is still of paramount concern in the clinics, caregivers and military medics. Herein, we designed a shape memory cryogel based on chitosan (C) and functionalized-dextran (D), incorporated with Kaolin (K) and calcium (Ca²⁺) as haemostatic agents. The developed cryogel (CDKCa) exhibits a uniform interconnected porous architecture with profound fluid absorption ability, rapid blood clotting, stable clot formation and good antibacterial activity. The CDKCa elucidates significantly less clotting time (~30 s; in-vitro) and increased aggregation and activation of platelets/red blood cells in comparison to the control groups and commercial dressings (Axiostat and QuikClot). The developed CDKCa also significantly reduced the aPTT and PT values by ~58 % and 31 % respectively, leading to the activation of intrinsic and extrinsic coagulation cascades. The CDKCa cryogel displays enhanced mechanical stability, flexibility and a good shape memory, a property quintessential to cease uncontrolled bleeding in irregular and non-compressible wounds. Further, the Kaolin and Ca²⁺ incorporated shape memory CDKCa cryogel demonstrates a rapid blood coagulation and stable clot formation in different compressible and non-compressible rat liver and femur hemorrhagic models. In summary, the endorsed results of CDKCa suggest that the design, fabrication and excellent clotting ability may attribute to high haemostatic efficiency of CDKCa dressing and have a great potential to prevent uncontrollable hemorrhages.

Effective adsorption of Orange G dye using chitosan cross-linked by glutaraldehyde and reinforced with quartz sand

In this study, quartz sand (QS) incorporated into a crosslinked chitosan-glutaraldehyde matrix (QS@Ch-Glu) was prepared and employed as an efficient adsorbent for the elimination of Orange G (OG) dye from water. The sorption process is adequately described by the pseudo-second order kinetic model and the Langmuir isotherm model with maximum adsorption capacities of 172.65, 188.18, and 206.65mg/g at 25, 35, and 45 °C, respectively. A statistical physics model was adopted to elucidate the adsorption mechanism of OG on QS@Ch-Glu. Calculated thermodynamic factors revealed that the adsorption of OG is endothermic, spontaneous, and occurs via physical interactions. Overall, the proposed adsorption mechanism was based on electrostatic attractions, n-π stacking interaction, hydrogen bonding interaction, and Yoshida hydrogen bonding. The adsorption rate of QS@Ch-Glu was still above 95 % even after 6 cycles of adsorption and desorption. Furthermore, QS@Ch-Glu demonstrated high efficiency in real water samples. All these findings demonstrate that QS@Ch-Glu is qualified for practical applications.

A review on remediation of dye adulterated system by ecologically innocuous "biopolymers/natural gums-based composites"

The mitigation of wastewater exploiting biopolymers/natural gums-based composites is an appealing research theme in today's scenario. The following review presents a comprehensive description of the polysaccharides derived from biopolymers (chitosan, collagen, cellulose, starch, pectin, lignin, and alginate) and natural gums (guar, gellan, carrageenan, karaya, moringa oliefera, tragacanth, and xanthan gum). These biopolymers/natural gums-based composites depicted excellent surface functionality, non-toxicity, economic and environmental viability, which corroborated them as potential candidates in the decontamination process. The presence of -OH, -COOH, and -NH functional groups in their backbone rendered them tailorable for modification/functionalization, and anchor an array of pollutants via electrostatic interaction, hydrogen bonding, and Van der Waals forces. Further, due to these functional moieties, these bio-based composites revealed an excellent adsorption capacity than conventional adsorbents. This review provides an overview of the classification of biopolymers/natural gums based on their origin, different ways of their modification, and the remediation of dye-contaminated aqueous environments employing diverse bio-based adsorbents. The isotherm, kinetic modelling along with thermodynamics of the adsorption process is discussed. Additionally, the reusable efficacy of these bio-adsorbents is reviewed.

The evolution of the global COVID-19 epidemic in Morocco and understanding the different therapeutic approaches of chitosan in the control of the pandemic

In 2020, Coronavirus disease (COVID-19), a new viral respiratory disease caused by a virus that belongs to Coronaviridae family, has been identified. It is a very severe flu that negatively affects the functions of the lung and other respiratory organs. COVID-19 virus can be transmitted between people either by touching an infected person or by direct contact with their respiratory droplets. Therefore, the COVID-19 virus has become a global concern due to its rapid spread and severity. Based on the World Health Organization report from 2 March 2020 to 24 October 2022, the total infected cases and deaths in Morocco are around 1,265,389 (3.46%) and 16,280 (0.04%), respectively. Recently, some scientists have found that chitosan, a polymer existed in nature, can inhibit COVID-19 infection and repair damaged tissue. Therefore, understanding chitosan mechanisms in controlling COVID-19, might lead to innovative strategies in the medical field, such as developing drugs against SARS-CoV-2, and replacing vaccines, which have negative side effects. This review aims to show the evolution of the COVID-19 pandemic worldwide, specifically in Morocco, its pathophysiology, and its ability to silence the immune system. This review also provides an overview of the treatments and measures applied to protect human beings and how chitosan acts and controls COVID-19.

Strengthening the surface and adsorption properties of diatomite for removal of Cr(VI) and methylene blue dye

The main purpose of this work was to boost the surface and adsorption characteristics of diatomite (D) through chemical modifications with chitosan (DC), chitosan/titanium isopropoxide (DCTi), or chitosan/ graphene oxide (DCGr), respectively. Physicochemical characteristics of the prepared samples were investigated using SEM, TEM, XRD, FTIR, TGA, and porosity measurements. The impact of such modifiers into the D surface on the removal efficiency of chromium (VI) ions and methylene blue dye was studied in an equilibrium mode. Langmuir and Freundlich isotherms were used to analyze the adsorption data. Modifiers considerably enhanced the surface and textural properties of D through insertion of the main surface functional groups of chitosan and graphene oxide together compared to chitosan and titanium isopropoxide together or chitosan alone. In addition, the total surface area and total pore volume parameters of the unmodified D sample were improved greatly from 16.5 m2/g, 0.036 cm3/g to 39.8 m2/g and 0.174 cm3/g for DCGr, while they were 17.7 m2/g and 0.132 cm3/g for DC. The best adsorption results were well-defined with the Langmuir isotherm equilibrium model. Accordingly, the DCGr sample exhibited the highest uptake of Cr(VI) (about 167 mg/g) and methylene blue (66.7 mg/g). Hence, the chemical modification strategy of diatomite performed by using chitosan and graphene oxide significantly boosted the surface active sites and porosity properties and thus gave rise to the high adsorption capacity of Cr(VI) and methylene blue dye from wastewater. Hence, these findings affirmed the validity of the current strategy for surface modification of diatomite with chitosan and graphene oxide.

Arsenic in drinking water: overview of removal strategies and role of chitosan biosorbent for its remediation

Accessibility to clean drinking water often remains a crucial task at times. Among other water pollutants, arsenic is considered a more lethal contaminant and has become a serious threat to human life globally. This review discussed the sources, chemistry, distribution, and toxicity of arsenic and various conventional technologies that are in option for its removal from the water system. Nowadays, biosorbents are considered the best option for arsenic-contaminated water treatment. We have mainly focused on the need and potential of biosorbents especially the role of chitosan-based composites for arsenic removal. The chitosan-based sorbents are economically more efficient in terms of their, low toxicity, cost-effectiveness, biodegradability, eco-friendly nature, and reusability. The role of various modification techniques, such as physical and chemical, has also been evaluated to improve the physicochemical properties of biosorbent. The importance of adsorption kinetic and isotherm models and the role of solution pH and pHPZC for arsenic uptake from the polluted water have also been investigated. Some other potential applications of chitosan-based biosorbents have also been discussed along with its sustainability aspect. Finally, some suggestions have been highlighted for further improvements in this field.

Ionic liquid treated leaves of Juglans regia as an adsorbent for the removal of methyl orange dye: experimental, computational, and statistical approach

The novel biosorbents prepared by surface modification from leaves of Juglans regia plant were exploited for removal of methyl orange dye from aqueous solution. The leaves in the form of dust and charcoal were separately impregnated with 1-butyl-3-methyl imidazolium bromide (I) to obtain adsorbents namely J. regia dust/charcoal impregnated with I (JRDI/JRCI) which were characterized using advanced analytical approaches. The impregnation of ionic liquid was confirmed by the appearance of new bands. Langmuir isotherm fitted well; the calculated adsorption capacity being 59.37 (JRDI) and 102.72 mg g^-1 (JRCI). The kinetic study revealed that sorption obeyed the pseudo-first order model; the experimental adsorption capacity being 53.53 (JRDI) and 86.82 mg g^-1 (JRCI) at selected conditions of pH 3, initial dye concentration 100 ppm, dosage of adsorbent 0.3 g and contact time 70 min. The mathematical models which predicted adsorption capacity as 51.5 (JRDI) and 82.1 mg g^-1 (JRCI) were found at par with experimental values. Fukui condensed functions revealed that adsorbents had electron deficient electrophilic reaction sites while dye had electron-rich nucleophilic reaction sites. The structural properties and good adsorption capability of adsorbents indicate that they could be used as potential, eco-friendly adsorbents for the treatment of negatively charged dye pollutants.

Reusable kaolin impregnated aminated chitosan composite beads for efficient removal of Congo red dye: isotherms, kinetics and thermodynamics studies

In this investigation, Kaolin (K) impregnated aminated chitosan (AM-CTS) composite beads were fabricated with multi-features including low-cost, high performance, renewable and ease of separation for adsorption of anionic Congo red (CR) dye. Characterization tools such as FTIR, XRD, SEM, TGA, BET, XPS and Zeta potential were thoroughly employed to confirm the successful formulation process. The results revealed that K@ AM-CTS composite beads displayed higher specific surface area (128.52 m²/g), while the thermal stability was prominently improved compared to pure AM-CTS. In addition, the adsorption equilibrium of CR dye was accomplished rapidly and closely gotten within 45 min. The removal efficiency was significantly enriched and reached 90.7% with increasing kaolin content up to 0.75%, compared to 20.3 and 58% for pristine kaolin and AM-CTS, respectively. Moreover, the adsorption process obeyed the pseudo-first order kinetic model, while data were agreed with the Freundlich isotherm model with a maximum adsorption capacity reached 104 mg/g at pH 6. Furthermore, D–R isotherm model demonstrated the physical adsorption process of CR dye, which includes the electrostatic interactions, ion exchange and H-bonding. Thermodynamics evidenced the spontaneous and endothermic nature of the adsorption process. Interestingly, the developed K@AM-CTS composites beads showed better reusability for eight consecutive cycles, suggesting their feasible applicability for adsorptive removal anionic dyes from polluted aquatic bodies.

Preparation of chitosan/tannin and montmorillonite films as adsorbents for Methyl Orange dye removal

A series of novel chitosan/tannin/montmorillonite (Cs/Tn/MMT) films were synthesised by loading different (from 0.2 to 0.5 wt%) and MMT (from 0.5 to 1.5 wt%) ratios, to be used as promising low-cost biosorbents for methyl orange (MO) removal from aqueous media. The prepared films were characterised using different techniques such as x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), water contact angle, optical properties, colourimetric measurement, porosity, swelling and thickness. The effects of various parameters, i.e. initial MO concentration, adsorbent dose, pH and temperature, were studied. The Cs/Tn0.2/MMT1 film showed a high removal efficiency of 95.62% and maximum adsorption capacity of 57.37 mg/g under the optimum adsorption conditions (initial methyl orange concentration 60 mg/L, pH 7 and 25 °C). The adsorption kinetic followed the pseudo second order kinetic model and the experimental data were a good fit for the Langmuir isotherm indicating a homogeneous and monolayer adsorption process. The thermodynamic parameters suggested physical adsorption and exothermic behaviour. Consequently, Cs/Tn/MMT films showed effective potential for the uptake of anionic dyes.

Effect of calcination temperature on morphology and phase transformation of MnO2 nanoparticles: A step towards green synthesis for reactive dye adsorption

Green synthesis of manganese oxide nanoparticles (NPs) was carried out by sol-gel method using Acacia Concinna fruit extract for removal of reactive dye. The effect of calcination temperature on its morphology was investigated. α-MnO₂ and Mn₃O₄ NPs were synthesized at 400 °C and 900 °C respectively and were characterized by PXRD, SEM, TEM, FTIR, BET, Raman and TGA. As-synthesized MnO₂ NPs were investigated for the adsorption of Reactive Blue 21 (RB-21) dye. The effect of pH, adsorbent dose, agitation speed, initial dye concentration and temperature on dye removal was explored. pH_pzc was calculated from zeta potential study showing positive surface charge below pH 3.18 resulting in electrostatic force of attraction between adsorbate and adsorbent. Both linear and non-linear regression approaches were utilised for the fitting of kinetic models and adsorption isotherms. Adsorption data follows a pseudo second order kinetics and fits well with the Freundlich isotherm model. Thermodynamic parameters such as ΔH^o, ΔS^o and ΔG^o were determined. The dye removal efficiency, in case of MnO₂ NPs at pH 3.0 was obtained to be 98% whereas for Mn₃O₄, no such dye adsorption was observed. The mechanism of adsorption was studied theoretically confirming π-π interaction and H-bonding between the MnO₂ and RB dye molecules.

Active and synchronous control of nitrogen and organic matter release from sediments induced with calcium peroxide

In order to realize the active and synchronous control of nitrogen (N) and organic matter (OM) release from sediments, this study compared the spatiotemporal changes in the physical, chemical, and biological indicators in the water system under different CaO₂ dosing modes. Results from 90-day incubation experiment showed that CaO₂ formed a dense barrier layer near its dosing position, improved the anoxic condition of water system, increased the physical adsorption of pollutants by sediments, and reduced the nutrients in overlying water, interstitial water, and sediments. Comprehensive comparison, the improvement effect of shallow injection group (I1) was the most obvious. Meanwhile, the activities of ammonia oxidizing bacteria and nitrite oxidizing bacteria near dosing position and those of denitrifiers and anammox bacteria adjacent to dosing site were significantly increased in all test groups (p < 0.01), thereby realizing the biological removal of N and OM in sediments. In addition, DO and ORP were steadily higher than 5 mg L^-1 and 100 mV in I1, where the NH₄⁺-N concentration in overlying water was stable below 1 mg L^-1, and the easily released N content in the upper (0-3 cm) and middle (4-6 cm) sediments decreased by 41.64% and 43.56%, respectively. Compared with the large pollutant flux in control (14.31 TN mg m^-2 d^-1 and 194.05 mg TCOD m^-2 d^-1), I1 completely inhibited the pollutant release and reduced the original nutrients in overlying water. In general, CaO₂ efficiently and synchronously controlled the endogenous release of N and OM under the combined actions of physical interception, physical adsorption, chemical oxidation, and biological transformation. Therefore, this study may provide valuable reference and guidance for the active and synchronous removal of N and OM in sediments and inhibition of endogenous pollutant release under anoxic condition.

Remazol Brilliant Blue R (RBBR) dye and phosphate adsorption by calcium alginate beads modified with polyethyleneimine

This study concerns the preparation of novel adsorbent prepared from calcium alginate bead modified with polyethyleneimine (PEI-CaAlg). The adsorption capacity of the PEI-CaAlg was examined by Remazol Brilliant Blue R (RBBR) and phosphate adsorption. PEI-CaAlg showed high removal efficiencies for RBBR (90.48%) and phosphate (88.10%). The removal of both RBBR and phosphate onto the PEI-CaAlg followed the Freundlich isotherm and the second-order model. The adsorption was studied in terms of thermodynamic and found to be feasible and spontaneous in nature. The reusability of the modified alginate beads was also examined up to five cycles. The removal efficiency was 90.48% at the first cycle and decreased to 75.15% at the end of the fourth cycle. The adsorption of color and phosphate from real textile wastewater was also instigated. The removal efficiencies for color and phosphate ions reached 80.24% and 90.00%, respectively. Therefore, the prepared PEI-CaAlg can be considered as a novel, eco-friendly, and cost-effective adsorbent for simultaneous dye and phosphate adsorption. PRACTITIONER POINTS: This study aims to modify the surface of calcium alginate beads with polyethyleneimine (PEI). The adsorption of RBBR and phosphate by the modified alginate beads (PEI-CaAlg) was investigated. PEI is an organic polymer with a linear/branch shape, which can increase the active sites on the adsorbent surface. PEI has one nitrogen atom in every three atoms provides a positive charge that can complex with the negatively charged molecules. The adsorption of RBBR and phosphate were carried out onto PEI-CaAlg.

Methylene blue removal with ZnO coated montmorillonite: thermodynamic, kinetic, isotherm and artificial intelligence studies

In this study, montmorillonite clay was coated with zinc oxide (ZnO) nanoparticles. The study's primary aim is to investigate the adsorption properties of zinc oxide coated montmorillonite adsorbent against methylene blue (MB), and determine ZnO's effectiveness in adsorption. First, the surface properties of the ZnO-coated montmorillonite (ZnO/MMT) adsorbent were determined by FTIR Spectroscopy, XRD, and SEM/EDS. In the adsorption studies, the effects of different parameters such as contact time (5-150 min), adsorbent dosage (0.05-0.5 g), initial concentration (50-200 mg/L), temperature (298-318 K), and initial pH (4-12) were investigated. In addition, a fuzzy model was developed by using adsorption parameters so that the removal rates could be calculated more quickly. Adsorption kinetics and equilibrium results were explained by the pseudo-second-order model and the Langmuir isotherm model, respectively. The highest adsorption capacity was calculated as 384.62 mg/g at 318 K. The enthalpy value was calculated as 2.16 kJ/mol. The entropy value was calculated as 0.04 kJ/mol K. The negative entropy value in the thermodynamic parameters calculated at all temperatures shows that the adsorption was spontaneous. According to the data we obtained, ZnO/MMT nanoparticles can be successfully applied for MB removal from aqueous solutions.

Application of chitosan-alginate bio composite for adsorption of malathion from wastewater: Characterization and response surface methodology

Agricultural effluents in aqueous media have caused serious threats due to adversely affect human health and the ecosystem. In this study, the low-cost easily accessible chitosan-alginate adsorbent was prepared for the removal of malathion from agricultural effluents using microemulsion method. The adsorbent was characterized using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The optimum experimental conditions, including adsorbent dosage (0.05-0.25 g), contact time (5-25 min), and concentration of malathion (5-25 mg L^-1) at five levels were studied using the composite central design (CCD) based on the response surface methodology (RSM). The highest removal percentage was obtained 82.35 with an adsorbent dosage of 0.18 g, contact time of 20 min, and initial concentration of 10 mg L^-1. The analysis of variance (ANOVA) was applied to assess the significance and adequacy of the model. The results revealed that quadratic model was proper for the prediction removal of malathion. The adsorption kinetics and isotherms were examined under optimal conditions. The Langmuir with a coefficient of determination (R²) = 0.99 and pseudo-second-order with R² = 0.99 were achieved as the best isotherm and kinetic models, respectively. The results showed that the chitosan-alginate biopolymer can be effective and affordable adsorbent for the removal of malathion from aqueous solution.

Organic carbon bioavailability: Is it a good driver to choose the best biological nitrogen removal process?

Organic carbon can affect the biological nitrogen removal process since the Anammox, heterotrophic and denitrifying bacteria have different affinities and feedback in relation to carbon/nitrogen ratio. Therefore, we reviewed the wastewater carbon concentration, its biodegradability and bioavailability to choose the appropriate nitrogen removal process between conventional (nitrification-denitrification) and Anammox-based process (i.e. integrated with the partial nitritation, nitritation, simultaneous partial nitrification and denitrification or partial-denitrification). This review will cover: (i) strategies to choose the best nitrogen removal route according to the wastewater characteristics in relation to the organic matter bioavailability and biodegradability; (ii) strategies to efficiently remove nitrogen and the remaining carbon from effluent in anammox-based process and its operating cost; (iii) an economic analysis to determine the operational costs of two-units Anammox-based process when compared with the commonly applied one-unit Anammox system (partial-nitritation-Anammox). On this review, a list of alternatives are summarized and explained for different nitrogen and biodegradable organic carbon concentrations, which are the main factors to determine the best treatment process, based on operational and economic terms. In summary, it depends on the wastewater carbon biodegradability, which implies in the wastewater treatment cost. Thus, to apply the conventional nitrification/denitrification process a COD_b/N ratio higher than 3.5 is required to achieve full nitrogen removal efficiency. For an economic point of view, according to the analysis the minimum COD_b/gN for successful nitrogen removal by nitrification/denitrification is 5.8 g. If ratios lower than 3.5 are applied, for successfully higher nitrogen removal rates and the economic feasibility of the treatment, Anammox-based routes can be applied to the wastewater treatment plant.

Influence of oil droplet behavior in electrochemical micromembrane cells on treating oil/water emulsions with low-salt concentrations

Although flow-through electrode has demonstrated its potential in treating oily wastewater, few studies noted influence of oil droplet behavior on treating oil/water emulsions. In order to explore the influence of oil droplet behavior in a flow-through electrode cell on treating oil/water emulsions with low-salt concentrations, an electrochemical micromembrane cell was applied to treat oil/water emulsions with 0-0.8 g/L NaCl. High chemical oxygen demand (COD) reduction (80-90%) was obtained in treating Sodium dodecylbenzene sulfonate (SDBS) or Tween 80 emulsion by flow-through electrode, while the later had the higher permeate flux (900 mL/min around). The low salt concentration (0.5 g/L NaCl) achieved high COD reduction (87%) and good permeate flux (600 mL/min). Observations using optical microscopy revealed severe deformation of the shape of the charged oil droplet at the flow-through electrode interface. The wetting of oil droplets at the electrode interface occurred when the membrane acted as an anode, which resulted in flow-through electrode fouling, and subsequently, the reduction in permeate flux and treatment efficiency. The results of this study offer an attractive option when using flow-through electrode to treat oil-in-water emulsions under low-salinity conditions.

Optimization of diosgenin extraction from Dioscorea deltoidea tubers using response surface methodology and artificial neural network modelling

INTRODUCTION

Dioscorea deltoidea var. deltoidea (Dioscoreaceae) is a valuable endangered plant of great medicinal and economic importance due to the presence of the bioactive compound diosgenin. In the present study, response surface methodology (RSM) and artificial neural network (ANN) modelling have been implemented to evaluate the diosgenin content from D. deltoidea. In addition, different extraction parameters have been also optimized and developed.

MATERIALS AND METHODS

Firstly, Plackett-Burman design (PBD) was applied for screening the significant variables among the selected extraction parameters i.e. solvent composition, solid: solvent ratio, particle size, time, temperature, pH and extraction cycles on diosgenin yield. Among seven tested parameters only four parameters (particle size, solid: solvent ratio, time and temperature) were found to exert significant effect on the diosgenin extraction. Moreover, Box-Behnken design (BBD) was employed to optimize the significant extraction parameters for maximum diosgenin yield.

RESULTS

The most suitable condition for diosgenin extraction was found to be solid: solvent ratio (1:45), particle size (1.25 mm), time (45 min) and temperature (45°C). The maximum experimental yield of diosgenin (1.204% dry weight) was observed close to the predicted value (1.202% dry weight) on the basis of the chosen optimal extraction factors. The developed mathematical model fitted well with experimental data for diosgenin extraction.

CONCLUSIONS

Experimental validation revealed that a well trained ANN model has superior performance compared to a RSM model.

Simvastatin nanoparticles loaded polymeric film as a potential strategy for diabetic wound healing: in vitro and in vivo evaluation

INTRODUCTION

The pleiotropic effects of statins are recently explored for wound healing through angiogenesis and lymph-angiogenesis that could be of great importance in diabetic wounds.

AIM

Aim of the present study is to fabricate nanofilm embedded with simvastatin loaded chitosan nanoparticles (CS-SIM-NPs) has been reported herein to explore the efficacy of SIM in diabetic wound healing.

METHODS

The NPs, prepared via ionic gelation, were 173nm ± 2.645 in size with a zeta potential -0.299 ± 0.009 and PDI 0.051 ± 0.088 with excellent encapsulation efficiency (99.97%). The optimized formulation (CS: TPP, 1:1) that exhibited the highest drug release (91.64%) was incorporated into polymeric nanofilm (HPMC, Sodium alginate, PVA), followed by in vitro characterization. The optimized nanofilm was applied to the wound created on the back of diabetes-induced (with alloxan injection 120 mg/kg) albino rats.

RESULTS

The results showed significant (p < 0.05) improvement in the wound healing process compared to the diabetes-induced non-treated group. The results highlighted the importance of nanofilms loaded with SIM-NPs in diabetic wound healing through angiogenesis promotion at the wound site.

CONCLUSION

Thus, CS-SIM-NPs loaded polymeric nanofilms could be an emerging diabetic wound healing agent in the industry of nanomedicines.

Fabrication of Fe3O4/ZIF-8 nanocomposite for simultaneous removal of copper and arsenic from water/soil/swine urine

In this study, a magnetic nanocomposite (denoted as FZ) was fabricated using Fe₃O₄and zeolitic imidazolate framework-8 (ZIF-8), based on a coprecipitation method. FZ could efficiently remove Cu²⁺(Cu(II)) and AsO₂^- (As(III)) ions simultaneously from water, soil, and swine urine samples through hydrogen bonding and electrostatic interactions. The Cu(II) and As(III) removal efficiencies of the optimal FZ sample increased gradually with time and reached 99.1% and 98.4%, respectively, in 180 min. The maximum adsorption capacities of FZ4 for Cu(II) and As(III) were determined to be 33.48 mg/g and 21.12 mg/g, respectively. Additionally, the FZ with a high saturation magnetization (49.8 emu/g) was easily recovered from aqueous solutions and soil samples. Furthermore, zebrafish experiments indicated that FZ possessed a high biosafety. Thus, this study introduces a promising method for treating water, soil, and swine urine samples contaminated with Cu(II) and As(III), and verifies that FZ is suitable for practical application.

Removal of Disperse Orange and Disperse Blue dyes present in textile mill effluent using zeolite synthesized from cenospheres

In this research, an efficient, ecofriendly method of using coal fly ash in the form of zeolite to treat wastewater containing dyes was studied. Response surface methodology involving Box-Behnken design was applied to a batch process to evaluate the effect of process parameters such as contact time, dye concentration, agitation speed, pH, and adsorbent dosage onto zeolite. Disperse Orange 25 (DO) dye showed a maximum of 96% removal under optimal conditions of contact time of 119 min, dye concentration of 38.00 mg/L, agitation speed of 158 rpm, pH of 6.10, and adsorbent dosage of 0.67 g/L, whereas 95.23% of Disperse Blue 79:1 (DB) dye removal was observed at adsorbent dose of 1.05 g/L, dye concentration of 26.72 mg/L, agitation speed of 145 rpm, pH of 5.68, and contact time of 122 min. It was concluded that cenosphere-derivatized zeolite adsorbent is efficient, ecofriendly, and economical and has high potential for the removal of DO and DB dyes from aqueous solutions.

Meso-microporous activated carbon derived from Raffia palm shells: optimization of synthesis conditions using response surface methodology

This study investigated the optimal synthesis conditions for the production of Raffia Palm Shell Activated Carbon (RPSAC) using phosphoric acid as activation agent. The optimization of the synthesis conditions was achieved using the Central Composite Design (CDD) in Response Surface Methodology (RSM). The influences of impregnation ratio, temperature, time and concentration on the specific surface area and yield of RPSAC were evaluated. Based on the CDD, 2FI and quadratic models were developed for the two responses. Analysis of Variance (ANOVA) was utilized to determine the significant factors and factor interactions for each response. All process variables except impregnation ratio were observed to significantly influence the quality of RPSAC. The optimal synthesis conditions for RPSAC were; 523.68 °C, 76.91%, and 103.83 min for temperature, concentration, and time respectively which provided a specific surface area and yield of 1762.92 m²/g and 77.98 % respectively. The Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX) analyses proved that RPSAC had a meso-micro-porous morphology with high carbon and oxygen contents. Fourier-transform infrared spectroscopy (FTIR) revealed the abundance of hydroxyl, carbonyl and carboxylic groups on RPSAC. X-ray Powder Diffraction (XRD) analysis showed that RPSAC composed mainly of amorphous and disordered microcrystalline phases ascribed to the high quartz content of the precursor. The Brunauer–Emmett–Teller (BET) surface area, average pore diameter, total pore volume, and pH_pzc of RPSAC were obtained as 456.10 m²/g, 0.25 cm³/g, 2.13 nm and 2.10 correspondingly. Thus, RSM was found to be an excellent and desirable tool for optimal synthesis of RPSAC that possess high surface area and porosity suitable for application in the adsorption of both large and small molecular sized pollutants such as dyes and fluoride in real and aqueous solution.

Chitosan-based hybrid materials for adsorptive removal of dyes and underlying interaction mechanisms

Environmental pollution by dyes molecules has become a subject of intensive research in recent years due to their hazardous effects on human health, organisms, and animals. Effective treatment and removal of dye molecules from the environmental matrices and water sources are of supreme concern. The deployment of cheap, safe, green, sustainable, and eco-friendly materials to remove these pollutants from water is the main challenge during the last decades. Chitosan and its derivatives/composites, as a cheap, easily available, and environmentally friendly sorbent, have attracted increasing attention for the removal of dye molecules. This review article focuses on the application of chitosan and chitosan-based smart adsorbents for the removal of dyes. Recent methods for the preparation of chitosan-based composites and their application in the removal of dyes are discussed. Moreover, the possible mechanisms for the interaction of chitosan and chitosan-based adsorbents with dyes molecules were evaluated. Finally, future prospects of using chitosan as an adsorbent for the removal of dye molecules are directed.

Removal of Uranyl Ion from Wastewater by Magnetic Adsorption Material of Polyaniline Combined with CuFe2O4

The magnetic adsorption material of polyaniline (PANI) with amino functional group combined with CuFe2O4 (CuFe2O4/PANI nanocomposite) has been described in this work. It has been characterized by TEM, XRD, XPS, BET, FTIR, and VSM, respectively. Significantly, it exhibits extremely high maximum adsorption capacity (322.6 mg/g) for removal of uranyl ions from wastewater at a pH of 4. The adsorption process is consistent with the quasisecond-order kinetic equation, and the isotherm and kinetic data are accurately described by the Langmuir isothermal adsorption model. Furthermore, the magnetic CuFe2O4/PANI displays stable adsorption performance for uranyl ions after five cycles of recovery in acid medium, which indicates it possesses good recovery due to its magnetism and excellent regeneration ability for reusability.

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.