Regeneration Studies Research Articles

Enhanced biosorptive incarceration of nitrate from aqueous solutions using novel green adsorbent: Performance optimization and mechanistic enlightenment

Excess nitrate contamination was lucratively addressed using the novel adsorbents prepared from waste seed pods of the Guilandina bonduc (L.) plant. Adsorbents BFP and EBFP (amino-grafted) were synthesized following a green pathway of thermo-chemical transformation. Adsorbents were successfully implemented for nitrate adhesion from natural and wastewater. The morphology of the adsorbents was studied using SEM-EDS, TGA, XRD, FTIR-ATR, and BET, including zeta potential and point of zero charges. The batch mode nitrate removal study was carried out using a colorimeter. The optimum efficiency in nitrate trapping was found to be 173.8 mg/g (EBFP) and 78.74 mg/g (BFP). The adsorption efficiency of the sorbents was further optimized using the RSM-CCD and found to be suitable. The batch sorption study was also supported by the column study with a breakthrough curve at 90% (EBFP) and 60% (BFP) for the regeneration study. The optimum value for EBFP was attained at an initial nitrate concentration of 110 mg/L, pH∼8, and a dosage of 12 g/L at room temperature within 75 minutes of contact. The Freundlich isotherm model and pseudo-second-order kinetics fit satisfactorily with the sorption trends followed by other isotherm and kinetic models. The influence of various competing ions e.g., PO43−, Cl−, HCO3−, SO42−etc., on nitrate adsorption study was investigated. The physicochemical sorption of nitrate was confirmed, and a plausible mechanism has been suggested accordingly. The field sample experiment, including the start-up opportunities with this work, has been highlighted. EBFP could be an excellent sorbent of choice at present that is ready for commercialization.

Remediation of multifarious metal ions and molecular docking assessment for pathogenic microbe disinfection in aqueous solution by waste-derived Ca-MOF.

The present study demonstrates an eco-friendly and cost-effective synthesis of calcium terephthalate metal-organic frameworks (Ca-MOF). The Ca-MOF were composed of metal ions (Ca2+) and organic ligands (terephthalic acid; TPA); the former was obtained from egg shells, and the latter was obtained from processing waste plastic bottles. Detailed characterization using standard techniques confirmed the synthesis of Ca-MOF with an average particle size of 461.9 ± 15nm. The synthesized Ca-MOF was screened for its ability to remove multiple metal ions from an aqueous solution. Based on the maximum sorption capacity, Pb2+, Cd2+, and Cu2+ ions were selected for individual parametric batch studies. The obtained results were interpreted using standard isotherms and kinetic models. The maximum sorption capacity (qm) obtained from the Langmuir model was found to be 644.07 ± 47, 391.4 ± 26, and 260.5 ± 14mgg-1 for Pb2+, Cd2+, and Cu2+, respectively. Moreover, Ca-MOF also showed an excellent ability to remove all three metal ions simultaneously from a mixed solution. The metal nodes and bonded TPA from Ca-MOF were dissociated by the acid dissolution method, which protonated and isolated TPA for reuse. Further, the crystal structure of Ca-MOF was prepared and docked with protein targets of selected pathogenic water-borne microbes, which showed its disinfection potential. Overall, multiple metal sorption capability, regeneration studies, and broad-spectrum antimicrobial activity confirmed the versatility of synthesized Ca-MOF for industrial wastewater treatment.

Crosslinked chitosan–montmorillonite composite and its magnetized counterpart for the removal of basic fuchsin from wastewater: Parametric optimization using Box-Behnken design

Treating wastewater polluted with organic dyestuffs is still a challenge. In that vein, facile synthesis of a structurally simple composite of chitosan with montmorillonite (CS-MMT) using glutaraldehyde as a crosslinker and the magnetized analogue (MAG@CS-MMT) was proposed as versatile adsorbents for the cationic dye, basic Fuchsin (FUS). Statistical modeling of the adsorption process was mediated using Box-Behnken (BB) design and by varying the composite dose, pH, [FUS], and contact time. Characterization of both composites showed an enhancement of surface features upon magnetization, substantiating a better FUS removal of the MAG@CS-MMT (%R = 98.43 %) compared to CS-MMT (%R = 68.02 %). The surface area analysis demonstrates that MAG@CS-MMT possesses a higher surface area, measuring 41.54 m2/g, and the surface analysis of the magnetized nanocomposite, conducted using FT-IR and Raman spectroscopies, proved the presence of FeO peaks. In the same context, adsorption of FUS onto MAG@CS-MMT fitted-well to the Langmuir isotherm model and the maximum adsorption capacities (qm) were 53.11 mg/g for CS-MMT and 88.34 mg/g for MAG@CS-MMT. Kinetics investigation shows that experimental data fitted well to the pseudo-second order (PSO) model. Regeneration study reveals that MAG@CS-MMT can be recovered effectively for repeated use with a high adsorption efficiency for FUS.

Dry reforming of methane over Ni/fibrous Zeolite-Y: optimization and regeneration studies

This study optimized the catalytic performance of Ni/Fibrous Zeolite-Y (Ni/FHY) toward dry reforming of methane (DRM). The optimization study was conducted under three independent variables employing the response surface methodology (RSM), trailed by a regeneration and stability studies. The study focused on the independent parameters of reaction temperature (A) (700 °C–900 °C), gas hourly space velocity (GHSV) (B) (15,000 mL/gcat −1.h−1 – 35,000 mL/gcat −1.h−1), and CH4/CO2 ratio (C) (1.0–3.0). The catalyst exhibited excellent activity (CH4 conversion = 94.5%, CO2 conversion = 88.3%, and H2/CO = 1.05) when all the parameters were under these optimum conditions (A = 833 °C, B = 24,962 mL/gcat −1.h−1, and C = 2.08). The catalytic stability study revealed an excellent performance of Ni/FHY where there was no indication of catalyst deactivation up to 30 h of time-on-stream (TOS). The outcome of the excellent catalytic activity can be explained by Ni-metal inclusion that enabled a substantial increase in the interaction between FHY and Ni, hence, subdued carbon formation. The regeneration study showed a good performance of regeneration owing to the capability of air to regenerate the catalyst completely, thus resulting in an excellent performance with 90 h TOS.

Adsorptive removal of organic pollutants from aqueous solutions using novel GO/bentonite/MgFeAl-LTH nanocomposite

The contamination of water with organic pollutants such as dyes and phenols is a serious environmental problem, requiring effective treatment methods. In the present study, a novel nanocomposite was synthesized by intercalating graphene oxide and bentonite clay into MgFeAl-layered triple hydroxide (GO/BENT/LTH), which was characterized using different techniques. The adsorption efficacy of the GO/BENT/LTH nanocomposite was assessed via the removal of two harmful organic water pollutants, namely methyl orange (MO) and 2-nitrophenol (2NP). The obtained results revealed that the maximum adsorption capacities (qmax) of MO and 2NP reached 3106.3 and 2063.5 mg/g, respectively, demonstrating the excellent adsorption performance of the nanocomposite. Furthermore, this study examined the effects of contact time, initial MO and 2NP concentrations, pH, and temperature of the wastewater samples on the adsorptive removal of MO and 2NP by the GO/BENT/LTH nanocomposite. The pH, zeta potential, and FTIR investigations suggested the presence of more than one adsorption mechanism. Thermodynamic investigations elucidated the exothermic nature of the adsorption of MO and 2NP onto the GO/BENT/LTH nanocomposite, with MO adsorption being more sensitive to temperature change. Additionally, regeneration studies revealed a marginal loss in the MO and 2NP removal with the repetitive use of the GO/BENT/LTH nanocomposite, demonstrating its reusability. Overall, the findings of this study reveal the promise of the GO/BENT/LTH nanocomposite for effective water decontamination.

Reforming of biomass-derived producer gas using toluene as model tar: Deactivation and regeneration studies in Ni and K-Ni catalysts

Within the syngas production from biomass gasification, tar removal constitutes a chief issue to overcome for advanced catalytic systems. This work investigates the performance of Ni and Ni–K catalysts for reforming of derived-biomass producer gas using toluene as model tar. At 750 °C and 60Lg−1h−1, the stability test (70 h) revealed stable performances (CO2, CH4 and C7H8 conversions of 60, 95 and 100%, correspondingly) uniquely for the Ni–K catalyst. Although the efficient protection towards coking let by K was demonstrated, TPO studies over the post-reacted systems still evidenced the presence of carbon deposits for both samples. Conducting three successive reaction/regeneration cycles with different gasifying agents (air, steam and CO2) at 800 °C for 1h, the capability towards regeneration of both catalytic systems was assessed and the spent catalysts were characterized by XRD, SEM and TEM. While none of the regeneration treatments recovered the performance of the unpromoted catalyst, the Ni–K catalysts demonstrated the capability of being fully regenerated by air and CO2 and exhibited analogous catalytic performances after a series of reaction/regeneration cycles. Hence, it is proved that the addition of K into Ni catalysts not only enhances the resistance against deactivation but enables rather facile regenerative procedures under certain atmospheres (air and CO2).

A response surface model to examine the reactive red 239 sorption behaviors on Rhizoclonium hieroglyphicum: isotherms, kinetics, thermodynamics and toxicity analyses.

The present study is an attempt to investigate the potentiality of Rhizoclonium hieroglyphicum in the removal of reactive red 239 (RR239) from aqueous solution and to assess the toxicity of the treated dye solution. Optimisation of the process variables namely dye and biosorbent concentrations, pH, temperature and incubation time for RR239 removal was performed using Response Surface Methodology (RSM) assisted Box Behnken Design (BBD) model. The recycling and regeneration efficiency of the dye adsorbed alga was evaluated using different eluents under optimized conditions. Further to understand the adsorption mechanism, isotherms, kinetics and thermodynamic studies were performed. UV-vis and FT-IR spectroscopy was employed to confirm the interaction between the adsorbate and biosorbent. The nature of the treated dye solution was assessed using phyto, microbial and brine shrimp toxicity studies. On the basis of quadratic polynomial equation and response surfaces given by RSM, 90% decolorization of RR239 was recorded at room temperature under specified optimal conditions (300mg/L of dye, 500mg/L of biosorbent, pH 8 and 72h of contact time). Desorption experiments demonstrated 88% of RR239 recovery using 0.1N acetic acid as an eluent and 81% of dye removal in regeneration studies. The data closely aligned with Freundlich isotherm (R2 - 0.98) and pseudo-second-order kinetic model (R2 - 0.9671). Thermodynamic analysis revealed that the process of adsorption was endothermic, spontaneous, and favorable. UV-Vis and FT-IR analyses provided evidence for adsorbate-biosorbent interaction, substantiating the process of decolorization. In addition, the results of phyto, microbial and brine shrimp toxicity assays consistently confirmed the non-toxic nature of the treated dye. Thus, the study demonstrated that R. hieroglyphicum can act as a potent bioremediation agent in alleviating the environmental repercussions of textile dyeing processes.

Chitosan Biocomposites with Variable Cross-Linking and Copper-Doping for Enhanced Phosphate Removal.

The fabrication of chitosan (CH) biocomposite beads with variable copper (Cu2+) ion doping was achieved with a glutaraldehyde cross-linker (CL) through three distinct methods: (1) formation of CH beads was followed by imbibition of Cu(II) ions (CH-b-Cu) without CL; (2) cross-linking of the CH beads, followed by imbibition of Cu(II) ions (CH-b-CL-Cu); and (3) cross-linking of pristine CH, followed by bead formation with Cu(II) imbibing onto the beads (CH-CL-b-Cu). The biocomposites (CH-b-Cu, CH-b-CL-Cu, and CH-CL-b-Cu) were characterized via spectroscopy (FTIR, 13C solid NMR, XPS), SEM, TGA, equilibrium solvent swelling methods, and phosphate adsorption isotherms. The results reveal variable cross-linking and Cu(II) doping of the CH beads, in accordance with the step-wise design strategy. CH-CL-b-Cu exhibited the greatest pillaring of chitosan fibrils with greater cross-linking, along with low Cu(II) loading, reduced solvent swelling, and attenuated uptake of phosphate dianions. Equilibrium and kinetic uptake results at pH 8.5 and 295 K reveal that the non-CL Cu-imbibed beads (CH-b-Cu) display the highest affinity for phosphate (Qm = 133 ± 45 mg/g), in agreement with the highest loading of Cu(II) and enhanced water swelling. Regeneration studies demonstrated the sustainability and cost-effectiveness of Cu-imbibed chitosan beads for controlled phosphate removal, whilst maintaining over 80% regenerability across several adsorption-desorption cycles. This study offers a facile synthetic approach for controlled Cu2+ ion doping onto chitosan-based beads, enabling tailored phosphate oxyanion uptake from aqueous media by employing a sustainable polysaccharide biocomposite adsorbent for water remediation by mitigation of eutrophication.

Novel high-efficient adsorbent based on modified gelatin/montmorillonite nanocomposite for removal of malachite green dye

Shortage of drinking water has gained potential interest over the last few decades. Discharged industrial effluent, including various toxic pollutants, to water surfaces is one of the most serious environmental issues. The adsorption technique has become a widely studied method for the removal of toxic pollutants, specifically synthetic dyes, from wastewater due to its cost-effectiveness, high selectivity, and ease of operation. In this study, a novel gelatin-crosslinked-poly(acrylamide-co-itaconic acid)/montmorillonite (MMT) nanoclay nanocomposites-based adsorbent has been prepared for removing malachite green (MG) dye from an aqueous solution. Modified gelatin nanocomposites were synthesized using a free-radical polymerization technique in the presence and absence of MMT. Various analytical instrumentation: including FTIR, FESEM, XRD, and TEM techniques were used to elucidate the chemical structure and surface morphology of the prepared samples. Using a batch adsorption experiment, Langmuir isotherm model showed that the prepared modified gelatin nanocomposite had a maximum adsorption capacity of 950.5 mg/g using 350 mg/L of MG dye at pH 9 within 45 min. Furthermore, the regeneration study showed good recyclability for the obtained nanocomposite through four consecutive reusable cycles. Therefore, the fabricated gelatin nanocomposite is an attractive adsorbent for MG dye elimination from aqueous solutions.

Comprehensive Development of a Cellulose Acetate and Soy Protein-Based Scaffold for Nerve Regeneration.

The elaboration of biocompatible nerve guide conduits (NGCs) has been studied in recent years as a treatment for total nerve rupture lesions (axonotmesis). Different natural polymers have been used in these studies, including cellulose associated with soy protein. The purpose of this report was to describe manufacturing NGCs suitable for nerve regeneration using the method of dip coating and evaporation of solvent with cellulose acetate (CA) functionalized with soy protein acid hydrolysate (SPAH). The manufacturing method and bacterial control precautions for the CA/SPAH NGCs were described. The structure of the NGCs was analyzed under a scanning electron microscope (SEM); porosity was analyzed with a degassing method using a porosimeter. Schwann cell (SCL 4.1/F7) biocompatibility of cell-seeded nerve guide conduits was evaluated with the MTT assay. The method employed allowed an easy elaboration and customization of NGCs, free of bacteria, with pores in the internal surface, and the uniform wall thickness allowed manipulation, which showed flexibility; additionally, the sample was suturable. The NGCs showed initial biocompatibility with Schwann cells, revealing cells adhered to the NGC structure after 5 days. The fabricated CA/SPAH NGCs showed adequate features to be used for peripheral nerve regeneration studies. Future reports are necessary to discuss the ideal concentration of CA and SPAH and the mechanical and physicochemical properties of this biomaterial.

Nylon fiber waste as a prominent adsorbent for Congo red dye removal

In this research nylon fibers wastes (NF) were fabricated into porous sheet using a phase inversion technique to be utilized as an adsorbent materials for Congo red dye (CR). The fabricated sheet denoted as NS was characterized using FTIR and XRD. The surface studies of the adsorbent materials using SEM and BET analysis reveals a highly pores structure with an average pore volume 0.61 cc/g and BET surface area of 767 m2/g. The adsorption studies of fabricated NS were employed into CR at different parameters as pH, effect of time and dye concentration. The adsorption isotherm and kinetic studies were more fit to Langmuir and pseudo second order models. The maximum adsorption capacity qmax reached 188 mg/g with removal percentage of 95 for CR concentration of 400 mg/L at pH 6 and 0.025 g NS dose for 10 ml CR solution. The regeneration study reveals a prominent adsorption behavior of NS with removal % of 88.6 for CR (300 mg/L) after four adsorption desorption cycles. Effect of incorporation of NaonFil Clay to NS was studied using Response Surface Methodology (RSM) modeling and reveals that 98.4% removal of CR could be achieved by using 19.35% wt. of fiber with 8.2 g/L dose and zero clay, thus at a predetermined parameters studies of NanoFil clay embedded into NS, there are no significant effect for %R for CR.

Regenerating Place: Highlighting the Role of Ecological Knowledge

As many local places globally suffer from ecological and social decline, sustainability research increasingly recognizes the critical importance of studying organizational efforts toward regenerating local communities and ecosystems. This emerging research, however, overlooks the role of ecological knowledge, that is, place-based understanding of the processes and functions of the ecosystems in which organizations operate. As such, we ask “How do organizations harness ecological knowledge to advance the regeneration of local places?” Through an inductive study of nine certified organic farming organizations on Vancouver Island, Canada, we find that organizations engage in three cyclical and closely interlinked practices of identifying, acquiring, and applying ecological knowledge which together enhance their organizational performance while contributing to regenerating the local social-ecological systems. Our empirically grounded model of leveraging ecological knowledge contributes to research on sustainability and place, and to studies of regeneration, by uncovering the specific practices that enable firms to develop place-based regenerative solutions.

Novel carbohydrate derived nanocomposite materials for efficient arsenic and fluoride elimination

A bottom-up methodology synthesizes the carbohydrate-derived graphene oxide (CGO). Further, the CGO, triiron tetraoxide (TTO) and bentonite (B) synthesizes the carbohydrate- novel composite material (CGO/TTO/B@1:2). The BET surface area of 428.551, 238.645 and 195.814 m2/g, respectively, obtained for the CGO, CGO/TTO and CGO/TTO/B@1:2. The composite material are promising in eliminating of As(III), As(V), and F− under various parametric conditions. The CGO/TTO shows the apparent sorption capacities of 26.59 and 35.97 mg/g for As(III) and As(V), respectively, while the CGO/TTO/B@1:2 exhibits the removal capacity of 17.81 mg/g for F−. Applying an extended Sips equation further elucidated the sorption capacities of 31.88 and 6.57 mg/g for As(V) and F−, respectively, during their simultaneous removal using CGO/TTO. Furthermore, the nanocomposite demonstrated fair stability and exceptional performance in dynamic experiments, including regeneration, repeated operations, natural water, and column studies. The CGO/TTO-Beads show loading capacities of 1.55x102 and 1.15x102 mg/g for As(III) and As(V) removal under the fixed-bed column studies. In contrast, CGO/TTO/B@1:2-Beads shows 1.54 mg/g loading capacity for F− removal.

Novel ZIF-8/CNC Nanohybrid with an Interconnected Structure: Toward a Sustainable Adsorbent for Efficient Removal of Cd(II) Ions.

Water pollution, especially by heavy metals, continues to pose significant challenges, emphasizing the urgency to develop sustainable processes to remove pollutants while developing sustainable materials derived from renewable sources. In the present research, a nanoscale adsorbent was prepared to remove cadmium (Cd(II)) ions from wastewater by hybridizing zeolitic imidazolate framework-8 (ZIF-8) with a cellulose nanocrystal (CNC). The prepared nanohybrid exhibited an interconnected structure in which the ZIF-8 particles were connected to each other via CNC nanoneedles. The hybridization of ZIF-8 with CNC caused a significant enhancement in the adsorption performance of the fabricated nanohybrid compared to pure ZIF-8, increasing its adsorption capacity by nearly 36%. The adsorption of ZIF/CNC followed the Langmuir isotherm model and pseudo-second-order kinetics models, remarking homogeneous adsorption onto the surface of ZIF/CNC, where chemisorption controlled the rate of adsorption. The thermodynamic study uncovered that the adsorption is spontaneous, endothermic, and entropy-governed as the randomness was increased at the solid-liquid interface. Additionally, the influence of operating variables, such as temperature, adsorbent dosage, pH, and ionic strength, was studied to mimic the adsorption capabilities of the adsorbent in real conditions. Accordingly, the optimum conditions were found to be at 45 °C and pH = 7 with a dosage of 0.4 g/L for the adsorbent. Moreover, the adsorption in a multimetal solution showed that the ZIF/CNC nanohybrid can remove various heavy metals, including Cd(II), Fe(III), Cu(II), and Pb(II) ions simultaneously. Finally, the regeneration study confirmed the great potential of the ZIF/CNC nanohybrid, which retained 94% of its initial adsorption capacity after 5 consecutive adsorption/desorption cycles.

Appraisal of the adsorption potential of novel modified gellan gum nanocomposite for the confiscation of methylene blue and malachite green

In the present investigation a novel, environmentally affable and economical, modified gellan gum nanocomposite (MAA-g-GG/Ppy/MMT) was fabricated via free-radical polymerization for the liquid-phase mitigation of Methylene blue (MB) and Malachite green (MG) dyes. The innovation of this work is substantiated by the intentional combination of diverse materials, the strategic incorporation of polypyrrole for enhanced adsorption, and the thoughtful addition of MMT as a nanofiller to address mechanical strength and improve adsorption capacity. The physico-chemical facets of MAA-g-GG/Ppy/MMT and its interaction with the dye molecules were elucidated using FT-IR, SEM-EDX, BET, TEM, and XRD techniques. The optimum conditions for the sorption of MB and MG were deemed to be dosage (1.2 g/L for both dyes), contact time (50 min for both dyes), initial MG/MB concentration (MB = 40 mg/L & MG = 30 mg/L), and pH (MB = 10 & MG = 7). The Freundlich isotherm was identified as the most suitable model, as evidenced by the highest R2 value (∼0.999), indicating multilayer adsorption. The pseudo second-order model appraised the kinetic data. Thermodynamic findings revealed the adsorption process to be spontaneous, viable and exothermic which was ascertained by negative ∆H⸰ values (−22.8 kJ/mol for MB and −18.3 kJ/mol for MG). The substantial Langmuir adsorption capacity (Qm: MG =185.185; MB = 344.827) can be ascribed to the reason for strong interactions between MAA-g-GG/Ppy/MMT and dyes. The high reliability of MAA-g-GG/Ppy/MMT was determined by the regeneration studies that worked up to four cycles for both dyes. The real water (distilled water, tap water, and river water) samples spiked with MG/MB demonstrated a substantial uptake of dyes (>85 %) and the marginal influence of ionic strength on the adsorptive potential of MAA-g-GG/Ppy/MMT validated its efficacy for the decontamination of real effluents. The forces of attraction between the dyes and MAA-g-GG/Ppy/MMT included van der Waals, electrostatic forces of attraction, and π-π interaction. This green, economical, and viable MAA-g-GG/Ppy/MMT will prove to be an efficient adsorbent for the decontamination process of sequestration of dyes to achieve a sustainable environment.

Bentonite/amino-functionalized cellulose composite as effective adsorbent for removal of lead: Kinetic and isotherm studies

In this study, bentonite/amino-functionalized cellulose composite (BAC) adsorbent was synthesized by intercalating the hexadecyl trimethyl ammonium bromide surfactant (HDTMA) into bentonite followed by exfoliating the HDTMA-modified bentonite (MB) into amino-functionalized cellulose (AC). The physicochemical properties of BAC were evaluated by FTIR, XRD, FE-SEM, EDX, TGA, and Zeta potential measurement. A series of batch mode adsorption experiments were carried out to identify the optimal adsorption conditions as a function of experimental variables such as pH of solution, uptake time, initial Pb2+ concentrations, BAC dosage, and assess both percent removal (%) and Pb2+ uptake (mg g−1). The result demonstrated that the synergetic advantage of combining HDTMA-modified bentonite (MB) and amino-functionalized cellulose (AC) in Pb2+ uptake (69 mg g−1) surpassed that of HDTMA-modified bentonite (12.14 mg g−1) and amino-functionalized cellulose (31.33 mg g−1) alone. Further, Pb2+ uptake onto BAC was higher than the HDTMA-modified bentonite/cellulose composite (BC) (42.12 mg g−1) due to the introduction of the amino group to cellulose through grafting with ethylenediamine (EDA). The adsorption of Pb2+ from aqueous solution by BAC fit well with pseudo - 2nd-order kinetic (R2 = 0.998) and Langmuir isotherm (R2 = 0.999) models. The kinetic study indicated that the active sites in the BAC exhibit heterogeneity and possess different activation energies for chemisorption. The monolayer attachment of Pb2+ onto the BAC surface was realized from the isotherm study, and the maximum predicted adsorption capacity was found to be 71.869 mg g−1. Regeneration studies showed that BAC maintained its good Pb2+ uptake capacity for up to four cycles.

Dental Stem Cell-Derived Exosomes: A Review of Their Isolation, Classification, Functions, and Mechanisms.

The scientific field concerned with the study of regeneration has developed rapidly in recent years. Stem cell therapy is a highly promising therapeutic modality for repairing tissue defects; however, several limitations exist, such as cytotoxicity, potential immune rejection, and ethical issues. Exosomes secreted by stem cells are cell-specific secreted vesicles that play a regulatory role in many biological functions in the human body; they not only have a series of functional roles of stem cells and exert the expected therapeutic effects, but they can also overcome the mass limitations of stem cells and are thus considered in the research as an alternative treatment strategy for stem cells. Since dental stem cell-derived exosomes (DSC-Exos) are easy to acquire and present modulating effects in several fields, including neurovascular regeneration and craniofacial soft and hard tissue regeneration processes, they are served as an emerging cell-free therapeutic strategy in various systematic diseases. There is a growing body of research on various types of DSC-Exos; however, they lack systematic elaboration and tabular summarization. Therefore, this review presents the isolation, characterization, and phenotypes of DSC-Exos and focuses on their current status of functions and mechanisms, as well as the multiple challenges prior to clinical applications.

Treatment of heavy metal ions from simulated water using adsorption process via modified iron magnetic nanocomposite

Heavy metals are considered hazardous elements because they are not biodegradable in the environment. Exposure to heavy metals leads to serious problems that affect human health and the aquatic environment. Removal of heavy metal ions from simulated water was employed for chitosan/iron nanocomposites (C-Fe2O3NPs). C-Fe2O3 was prepared from chitosan solution and iron salt. The characterization of C-Fe2O3 was carried out using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), and X-ray diffractometry (XRD). To determine the morphological structure, functional groups, and physicochemical properties. Determination of the optimum operating experimental conditions that result in the highest efficiency for heavy metal ions was investigated, such as contact duration (0–60 min), concentration (0.5, 1, 2, 3, and 5 mg/L), and adsorbent dose (0.1–0.5 g/L). Subsequently, the application of modified C-Fe2O3 in batch system for the elimination of Cu, Cr, Pb, Zn, and Se from simulated water was carried out. The results showed that EDX displayed the existence of iron, indicating the presence of iron nanoparticles. Also, the XRD and XRF showed the presence of iron oxide in the crystalline phase. The optimal conditions of the breakthrough curve, such as column height, flow rate, and contact time, were also examined. The results showed that the optimal conditions in the column system were a height of 10 cm, a flow rate of 5 mL/min, and a concentration of 3 mg/L. The kinetic information obtained was best modeled with the pseudo second-order model, and the experimental results fit the Langmuir model. High removal rates for Cu, Cr, Zn, Se, and Pb reached 99.8%, 93.8%, 98.8%, 99.8%, and 97.8%, respectively were achieved. The regeneration study indicated the good shelf life of iron magnetic NPs, which was 4.2%. In conclusion, C-Fe2O3 NPs are a potential adsorbent for heavy metal decontamination from water.

Defluoridation using pinecone-based activated carbon: Adsorption isotherm, kinetics, regeneration, and co-ions effect investigation

In this work, cheap and locally available pinecones of Pinus kiseya were used as a precursor to prepare activated carbon using single-step KOH activation for the removal of fluoride from water. The prepared activated car-bon?s BET surface area, and total pore volume, were determined as 972.13 m2 g-1 and 0.469 cm3 g-1, respectively. Batch adsorption studies were evaluated at different contact times, solution pH, adsorbent dose and concentration to obtain the optimum conditions for maximum adsorption. The adsorption data were fitted with the the isotherm models (Langmuir, Freundlich ad Temkin isotherm model) and the adsorption kinetic models. The experimental data were found to best fit using the Langmuir isotherm which confirmed the formation of a monolayer coverage with a maximum adsorption capacity of 2.845 m2 g-1. The adsorption kinetics was well described by the pseudo-second-order model. A study on the effects of co-existing ions showed that fluoride adsorption cap-acity was observed to decrease in the order: CO32- > SO42- > NO3- > Cl-. The regeneration studies were investigated to determine the reusability of the spent adsorbent. In summary, these findings demonstrated substantial evidence that the activated carbon can be prepared from P. kiseya cones as an eco-friendly adsorbent for the removal of ions such as fluoride from water.

Experiment investigation of CO2 regeneration properties for JLOX500 and 13X in various ways

This work presented a comparative study of CO2 regeneration for two kinds of X zeolites (JLOX500 and 13X) in different ways, such as vacuum, CH4 purge and heating regeneration. The materials characteristics of samples were determined by EDS and BET. The adsorption capacities of CO2 for original and regenerated samples were identified as the single-point adsorption dosing CO2 at 800 kPa. The results showed that JLOX500 had larger original adsorption capacity (OAC) of CO2 (4.83 mmol/g) than that of 13X (4.10 mmol/g). In vacuum regeneration, the regenerated adsorption capacities (RAC) of CO2 for both samples were almost same at all vacuum pressures (1 ~ 100 kPa); in CH4 purge regeneration, the regeneration degree (RD) for both samples were identical to each other with the flowrates (50 ~ 300 mL/min); in heating regeneration, JLOX500 had larger RACs than 13X at temperatures (50 ~ 300 °C), but had less RDs. The RACs and RDs for JLOX500 and 13X both increased as the regeneration time was prolonged. 13X would be more efficient adsorbent in the vacuum regeneration, whereas JLOX500 performed better in purge and heating regeneration.