Microwave-assisted Hydrothermal Process Research Articles

The effect of microwave-assisted hydrothermal treatment on physicochemical and functional properties of wheat, barley, and rye flours

The aim of this study was to investigate the effect of microwave-assisted hydrothermal process on color, solvent holding capacity, damaged starch content, resistant starch content, gelation and textural properties of wheat, barley, and rye flours. The hydrothermal treatment was conducted by adjusting the moisture content of the flours to 20, 25, 30, 35% following drying of the hydrated flours using a modified microwave oven until the moisture content fell below 8%. As a result, a general increase was observed in solvent (water, lactic acid, sucrose, and sodium carbonate) holding capacity, damaged starch content, b* value, chroma (saturation), redness, ΔE value, and gelatinization temperature of the flours regardless of the cereal type. The variations were more pronounced at higher initial moisture contents. On the contrary, the resistant starch content, L* value, whiteness, and breakdown viscosity decreased as a result of the treatment. The hydrothermal treatment resulted in an increase in maximum viscosity, setback viscosity, and gel hardness for wheat flour, whereas it led to a decrease in these parameters for treated barley and rye flours. Moreover, the impact of the treatment varied depending on the initial moisture content, with a more significant effect observed at moisture contents exceeding 25%.

Microwave-assisted hydrothermal processing of pine nut shells for oligosaccharide production

AbstractPine nut shells, a biomass residue from the Mediterranean Pinus pinea pine nut industrial processing, were treated by microwave-assisted autohydrolysis to produce xylo-oligosaccharides. Microwave-assisted processes provide alternative heating that may reduce energy input and increase overall process efficiency. The autohydrolysis treatments were performed under isothermal and non-isothermal operations within a wide range of operational conditions (temperature/reaction times) covering several severity regimes (as measured by the log R0 severity factor). The composition of the autohydrolysis liquors was determined in terms of oligo- and monosaccharides, aliphatic acids and degradation compounds. The process was highly selective towards hemicelluloses hydrolysis and liquid streams containing a mixture of oligomeric compounds (mainly xylo-oligosaccharides) could be obtained under relatively mild operation conditions (190 °C, 30 min) with a maximal oligosaccharides’ concentration of 18.48 g/L. The average polymerization degree of the obtained oligosaccharides was characterised by HPLC, showing that for the optimal conditions a mixture of oligomers with DPs from 2 to 6.

Potential of microwave-assisted hydrothermal modification for enhanced fly ash adsorption capacity toward to heavy metals: A comprehensive investigation of adsorbent characterization, isotherms, kinetics, and thermodynamics

ABSTRACT Heavy metal contamination is a major concern, and the adsorption process is regarded as one of the most efficient water remediation processes to deal with it. Herein, we modified fly ash by a microwave-assisted hydrothermal process to enhance its adsorption capacity and tested the material toward Cd(II) and Cu(II). Characterization of the adsorbents was performed by several techniques in detail to elucidate considerable structural changes such as cracking of spherical morphology, increase in surface area and changing of the chemical composition. Then batch adsorption was performed under different conditions to investigate the equilibrium, kinetics, and thermodynamics of the process. NaOH-modified fly ash considerably has a higher adsorption performance than that of the as-received sample for both ions. The highest adsorption capacity of modified fly ash was achieved as 133.8 and 95.7 mg/g for Cd(II) and Cu(II), respectively. The kinetics and isotherms could be perfectly reflected by a pseudo-second-order rate equation and the Freundlich model, while thermodynamics confirmed the endothermicity of the process.

Carbon Dots' Potential in Wound Healing: Inducing M2 Macrophage Polarization and Demonstrating Antibacterial Properties for Accelerated Recovery.

Bacterial infections and persistent inflammation can impede the intrinsic healing process of wounds. To combat this issue, researchers have delved into the potential use of carbon dots (CDs) in the regulation of inflammation and counteract infections. These CDs were synthesized using a microwave-assisted hydrothermal process and have demonstrated outstanding antibacterial and antibiofilm properties against Gram-positive and Gram-negative bacteria. Additionally, CDs displayed biocompatibility at therapeutic concentrations and the ability to specifically target mitochondria. CD treatment effectively nullified lipopolysaccharide-triggered reactive oxygen species production by macrophages, while simultaneously promoting macrophage polarization toward an anti-inflammatory phenotype (M2), leading to a reduction in inflammation and an acceleration in wound healing. In vitro scratch assays also revealed that CDs facilitated the tissue-repairing process by stimulating epithelial cell migration during reepithelialization. In vivo studies using CDs topically applied to lipopolysaccharide (LPS)-stimulated wounds in C57/BL6 mice demonstrated significant improvements in wound healing due to enhanced fibroblast proliferation, angiogenesis, and collagen deposition. Crucially, histological investigations showed no indications of systemic toxicity in vital organs. Collectively, the application of CDs has shown immense potential in speeding up the wound-healing process by regulating inflammation, preventing bacterial infections, and promoting tissue repair. These results suggest that further clinical translation of CDs should be considered.

Preparation of nano-scale ferric hexacyanoferrate using coal ash by microwave-assisted hydrothermal process for cesium removal

The removal of radioactive cesium (Cs+) has received considerable attention owing to its chemotoxicity and radiotoxicity. This study presents a method for producing ferric hexacyanoferrate nanoparticles (Prussian blue, PB), using recycled magnetic coal ash (M-CA) as an effective and selective adsorbent for Cs+ removal. A microwave-assisted hydrothermal technique was employed to recover the Fe solution from M-CA and a simple sol–gel technique was used to synthesize PB nanoparticles. The PB nanoparticles exhibited cubic cluster structures with an average size of 20.67 nm. Their Cs+ adsorption capacity reached 213.061 mg/g, significantly surpassing the capacities of absorbents reported in previous studies. Cs+ was observed to be associated with localized adsorption sites on the PB surfaces, with minimal internal diffusion. In addition, the hydrated radius of Cs+ emerged as a critical factor influencing its adsorption onto PB surfaces, enabling the efficient removal of Cs+ even in the presence of competing ions. These findings offer valuable insights for the straightforward synthesis of highly efficient and selective adsorbents for radioactive substances, as well as the recovery of valuable materials from industrial solid waste.

Tin sulfide supported on cellulose nanocrystals-derived carbon as a green and effective catalyst for CO2 electroreduction to formate

This work reports a whole green two-step approach for the synthesis of novel catalysts for efficient CO2 conversion. A conductive carbon support was firstly obtained via pyrolysis of cellulose nanocrystals (CNCs), and the carbon surface was successively decorated with tin sulfide (SnS) through a microwave-assisted hydrothermal process. The morphology and carbon structure were characterized by field emission scanning electron microscopy and Raman spectroscopy, and the presence of SnS decoration was confirmed by X-ray photoelectron spectroscopy and X-ray diffraction analyses. The SnS supported on CNC-derived carbon shows enhanced catalytic activity for the CO2 conversion to formate (HCOO−). Good selectivity of 86% and high partial current density of 55 mA cm−2 are reached at − 1.0 V vs. reversible hydrogen electrode in KHCO3 electrolyte. Additionally, the mass activity of the composite catalyst achieves a value as high as 262.9 mA mgSn−1 for HCOO− formation, demonstrating good utilization efficiency of Sn metal. In this work, the low-cost CNC-derived carbon is evidenced to be easily decorated with metal species and thus shows high versatility and tailorability. Incorporating metal species with conductive high-surface carbon supports represents an effective strategy to realize active and stable electrocatalysts, allowing efficient utilization of metals especially the raw and precious ones.Graphical abstract

Revolutionizing Gram-negative bacteria detection: FLIM and multicolor imaging based selective interaction study using colistin passivated carbon dots

The rising prevalence of antibiotic-resistant Gram-negative bacteria presents a major challenge for healthcare and requires the development of new and effective detection techniques. In this study, we present a novel and simple method for the selective detection of Gram-negative bacteria using multi-emissive colistin-passivated carbon dots (m-CCD) based on Fluorescence Lifetime (FLT) response and bioimaging. The m-CCD was synthesized using a one-step microwave-assisted hydrothermal process, and its interaction with Gram-negative bacteria was studied using Fluorescence Lifetime Imaging Microscopy (FLIM) and automated Confocal Laser Scanning Microscopy (CLSM). The investigations revealed a notable reduction in the FLT of m-CCD-treated Gram-negative bacteria (average lifetime of m-CCD, (τavg) m-CCD is 3.91 ns and m-CCD treated Gram-negative bacteria, (τavg) m-CCD-bac is 1.57 ns), demonstrating the selective interaction between them. Furthermore, the CLSM data revealed high specificity of m-CCD for Gram-negative bacteria, even in polymicrobial samples. Importantly, we also demonstrate that this method can quantify Escherichia coli (E. coli) cells with two linear ranges such as 3.40 × 105 – 9.80 × 105 CFU mL−1 and 6.90 × 107–4.14 × 108 CFU mL−1 in standard culture and real samples such as tap water and human urine with a limit of detection ∼ 3.68–4.89 × 104 CFU mL−1. This straightforward method has great potential for the rapid and selective detection of Gram-negative bacteria, paving the way for early diagnosis and treatment of bacterial infections.

Microwave-assisted synthesis of N/S-doped CNC/SnO2 nanocomposite as a promising catalyst for oxygen reduction in alkaline media

In this study, we report an all-green approach for the synthesis of novel catalysts for oxygen reduction reaction (ORR) via a simple two-step procedure. In particular, conductive cellulose nanocrystals (CNCs) were obtained via pyrolysis, and a successive microwave-assisted hydrothermal process was employed to activate the carbon lattice by introducing sulfur (S) and nitrogen (N) dopants, and to decorate the surface with tin oxide (SnO2) nanocrystals.The successful synthesis of N/S-doped CNC/SnO2 nanocomposite was confirmed by X-ray Photoelectron Spectroscopy analysis, Energy Dispersive X-ray microanalysis, X-ray Diffraction and Field Emission Scanning Electron Microscopy. The synergistic effects of the dopants and SnO2 nanocrystals in modifying the catalytic performance were proved by various electrochemical characterizations. Particularly, the nanocomposite material reaches remarkable catalytic performance towards the ORR, close to the Pt/C benchmark, in alkaline environment, showing promising potential to be implemented in alkaline fuel cell and metal-air battery applications.

Photocatalytic Degradation of Methylene Blue and Anticancer Response of In2O3/RGO Nanocomposites Prepared by a Microwave-Assisted Hydrothermal Synthesis Process.

The incorporation of graphene with metal oxide has been widely explored in various fields, including energy storage devices, optical applications, biomedical applications, and water remediation. This research aimed to assess the impact of reduced graphene oxide (RGO) doping on the photocatalytic and anticancer properties of In2O3 nanoparticles. Pure and In2O3/RGO nanocomposites were effectively synthesized using the single-step microwave hydrothermal process. XRD, TEM, SEM, EDX, XPS, Raman, UV-Vis, and PL spectroscopy were carefully utilized to characterize the prepared samples. XRD data showed that synthesized In2O3 nanoparticles had high crystallinity with a decreased crystal size after RGO doping. TEM and SEM images revealed that the In2O3 NPs were spherical and uniformly embedded onto the surface of RGO sheets. Elemental analysis of In2O3/RGO NC confirmed the presence of In, O, and C without impurities. Raman analysis indicated the successful fabrication of In2O3 onto the RGO surface. Uv-Vis analysis showed that the band gap energy was changed with RGO addition. Raman spectra confirmed that In2O3 nanoparticles were successfully anchored onto the RGO sheet. PL results indicated that the prepared In2O3/RGO NCs can be applied to enhance photocatalytic activity and biomedical applications. In the degradation experiment, In2O3/RGO NCs exhibited superior photocatalytic activity compared to that of pure In2O3. The degradation efficiency of In2O3/RGO NCs for MB dye was up to 90%. Biological data revealed that the cytotoxicity effect of In2O3/RGO NCs was higher than In2O3 NPs in human colorectal (HCT116) and liver (HepG2) cancer cells. Importantly, the In2O3/RGO NCs exhibited better biocompatibility against human normal peripheral blood mononuclear cells (PBMCs). All the results suggest that RGO addition improves the photocatalytic and anticancer activity of In2O3 NPs. This study highlights the potential of In2O3/RGO NCs as an efficient photocatalyst and therapeutic material for water remediation and biomedicine.

Investigations on the lithium-ion and sodium-ion insertion behavior of amorphous sodium iron carbonophosphate using N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide based ionic liquid electrolyte

In this article, we investigate the electrochemical performance of the amorphous sodium iron carbonophosphate upon transitioning from organic electrolytes (lithium hexafluorophosphate (LiPF6) –ethylene carbonate (EC): diethyl carbonate (DEC) based) to ionic-liquid (N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide; PMP-FSI) based electrolytes. The amorphous sodium iron carbonophosphate is synthesized using microwave-assisted hydrothermal process to obtain the desired phase and microstructure. The nanoparticle morphology, along with the amorphous structure, results in excellent electrochemical properties when tested as cathode for lithium-ion and sodium-ion batteries with organic and ionic-liquid based electrolytes. It is observed that the room-temperature and high-temperature (∼60 °C) cycling performance is superior when ionic-liquids are used instead of organic electrolytes, resulting in nearly fade-free electrochemical cells. Specific capacity retention of ∼97% is reported after 500 cycles with 3 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/PMP-FSI ionic-liquid at a specific current density of 400 mAg−1 (room temperature), in comparison to ∼70% after 500 cycles for 1 M LiPF6 in EC: DEC = 1:1. At high temperatures (∼60 °C), ionic-liquids outperform the conventional organic electrolytes in terms of capacity retention and rate capability. Post-mortem analysis of the electrodes indicates that a dense and ionically conductive protective film, composed of anion-reduced moieties, is responsible for the superior high-temperature performance of amorphous sodium iron carbonophosphate with the ionic-liquids.

An Exploration of Modified Microwave-assisted Rapid Hydrothermal Liquefaction Process for Conversion of Palm Kernel Shells to Bio-oil

Bio-oil is one of the potential resources to address the sustainable energy development and environmental issues. Microwave-assisted Rapid Hydrothermal Liquefaction Process is one of the popular techniques that is used to extract bio-oil from biomass. In this paper, the bio-oil has been extracted from Palm Kernel Shells by using microwave-assisted and conventional heating pyrolysis processes. A modified heating mantle apparatus are used to conduct the experiment for extracting the bio-oil. The experiments are conducted by varying the hydrothermal temperature and time for both techniques to achieve the conversion of the bio-oil from the raw material. It is found that the yield of bio-oil for microwave-assisted Rapid Hydrothermal Liquefaction Process at 350°C and 400°C are from 10.70 wt% to 25.60 wt% within hydrothermal time 6, 9 and 12 minutes. The pH value of the bio-oil is acidic with the range from 3 to 4. The calorific value of the bio-oil is varied from 24 to 26 MJ/kg for both conversion methods. Fourier Transform Infrared Spectroscopy (FTIR) result reveals that multiple functional groups (alcohol, aldehydes, carboxylic acid and ketones) are present in the PKS bio-oil.

A structured CoWO4 synthesized by microwave-assisted hydrothermal process as electrode for hybrid supercapacitor

A structured carambola-like CoWO4 was fast prepared by a microwave-assisted hydrothermal method with the help of urea and NH4F. Physical characterization indicated that the as-obtained CoWO4 displayed a large specific surface area, high dispersion and self-selected orientation of crystal growth. Further electrochemical tests presented a high specific capacity of 492.0 C[Formula: see text]⋅[Formula: see text]g[Formula: see text] at 1 A[Formula: see text]⋅[Formula: see text]g[Formula: see text], low internal resistance and excellent cycle stability as 137.3% capacity maintenance after 8000 cycles at 20 A[Formula: see text]⋅[Formula: see text]g[Formula: see text]. These excellent electrochemical properties for the as-obtained material indicate that CoWO4 has great potential as hybrid supercapacitor electrode materials. This work also provides a new and effective solution for regulating the morphology of CoWO4-based hybrid supercapacitor materials to further improve the electrochemical performance.

Towards development of sustainable metallic superhydrophobic materials

In the present study, an environment friendly, scalable, and cost-effective approach is proposed, combining thermo-mechanical and microwave-assisted hydrothermal processing techniques, resulting in the augmentation of nanoscale structures on metallic surfaces. The thermo-mechanical processing of the aluminium alloy performed at different strain rates resulted in significant grain refinement (∼ 1 µm for processed and ∼ 30 µm for unprocessed samples). After hydrothermal treatment, highly dense and networked nanostructured morphology was evoked by refined grains. Post silanization, samples exhibited high contact angle (θs > 155°) with a low tilt angle (θt < 10°) and CAH (< 5°). The low adhesion with water (∼ 16 µN) for the processed sample (∼ 50 μN for unprocessed) with utmost refined grains is attributed to the high interfacial energy of Cassie state (EC−B>1.0J) due to effective entrapment of air. The processed samples were highly de-wetting and mechanically resilient owing to the strong negative capillary pressure (PC > 1100 kPa) generated by highly dense networked nanostructures. As a result of thermo-mechanical processing, samples displayed higher resilience to abrasion, simulated rain, and long-term immersion tests with low tilt angles (θt < 10°) and CAH (< 5 °). This paper provides a practical approach to achieve anti-wetting surfaces in various industrial settings.

Structure and Magnetism of Iron-Substituted Nickel Hydroxide Nanosheets

Nanosheets composed of stacked atomic layers exhibit unique magnetic, electrical, and electrochemical properties. Here, we report the effect of iron substitution on the structure and magnetism of nickel hydroxide, Ni(OH)2, nanosheets. Ni(OH)2 and iron-substituted Ni(OH)2 (5, 10, 20, and 50 atomic % Fe substitution) were synthesized using a rapid microwave-assisted hydrothermal process. Scanning and transmission electron microscopy show the materials are polycrystalline nanosheets that aggregate into micron-sized clusters. From X-ray diffraction characterization, iron substitutes into the α-Ni(OH)2 lattice up to 20 at. % substitution. The nanosheets exhibit different in-plane and through-plane domain sizes, and Fe substitution affects the nanocrystallite shape anisotropy. The magnetic response differs with Fe substitution: 0% and 5% Fe are ferromagnetic, while samples with 10% and 20% Fe are ferrimagnetic. The competing interactions between magnetization sublattices and the magnetic anisotropy due to the crystalline and shape anisotropy of the nanosheets lead to magnetization reversal at low temperatures. The correlation between higher coercivity and larger nanocrystalline size anisotropy with higher Fe % supports that magnetic anisotropy contributes to the observed ferrimagnetism. The interplay of morphology and magnetic response with Fe-substituted Ni(OH)2 nanosheets points to new ways to influence electron interactions in layered materials which has implications for batteries, catalysis, sensors, and electronics.

Microwave-assisted hydrothermal solution process for accelerated formation of 3D hierarchical flowery anatase-TiO2 microspheres with excellent photocatalytic activity

A microwave-assisted hydrothermal solution synthesis methodology is used to prepare 3D hierarchical flowery TiO2 microspheres quickly and without calcination.

Fabrication of interface-engineered Ni/NiO/rGO nanobush for highly efficient and durable oxygen reduction

Developing non-noble metal electrocatalytic cathode materials with high catalytic activity, low cost and good durability is crucial for fuel cell applications on a large scale. Herein, we presented a novel Ni/NiO/rGO nanobush by controlled hydrolysis, anchoring nucleation and microwave-assisted hydrothermal process, as a highly effective cathode catalyst material for oxygen reduction reactions in an alkaline medium. The as-prepared Ni/NiO/rGO nanobush not only had abundant interface structures that can promote electron transfer but also maximized the exposure of active sites. The effects of complexing agent and precipitant on the interrelated hierarchical structure, the function of the composite interfaces and the oxygen reduction reaction (ORR) performance of the composite catalyst were subsequently investigated in detail. As a novel non-noble metal ORR electrocatalyst, Ni/NiO/rGO nanobush, of which the half-wave potential was 0.812 V, presented excellent catalytic efficiency in an alkaline solution with an electron transfer number of 3.92. After reacting for 20000 s, the retention rate of its current density still reached 87.9% and the current density was only lost by 9% after reacting for 1000s through the anti-methanol poisoning test. Thus, the long-term stability and methanol tolerance are superior to that of commercial Pt/C catalysts. This study provides a new structural engineering strategy for the non-noble metal ORR electrocatalyst composite.

Microwave-assisted extraction of Ulva spp. including a stage of selective coagulation of ulvan stimulated by a bio-ionic liquid

Microwave-assisted hydrothermal processing was proposed to recover high valuable compounds with antioxidant and gelling features from Ulva spp. green seaweed. The influence of the extraction conditions on the solubles, ulvan fraction and residual solid phase was studied to achieve a global valorization of the seaweed. A particular emphasis was placed on the selective coagulation of ulvan stimulated by a bio-ionic liquid during the extraction process. The achieved outcomes indicated that the selected microwave treatment exhibited a notable impact on the phytochemical properties of the soluble extracts, with the highest values of sulfate and protein content at 160 °C, and the highest antioxidant features at 200 °C. The most prominent molecular weight distributions were also identified for systems hydrothermal treated at 160 °C. The ulvan analyses showed that those extracted after microwave treatment at 160 °C showed the highest yields, molecular weight and the strongest gel features from the rheological point of view. The presence of the chloride chlorine during the extraction process favored the ulvan performance and the enhancement of the corresponding viscoelastic properties.

Exposed (040) facets of BiVO4 modified with Pr3+ and Eu3+: Photoluminescence emission and enhanced photocatalytic performance

BiVO4 materials are promising candidates for photocatalytic applications due to their optical and electronic properties, and among several methodologies, the doping of these materials has shown good results for applications. In this work, we prepared samples of BiVO4 in tetragonal zirconia and monoclinic scheelite phase doped with Europium and Praseodymium through the co-precipitation method followed by microwave-assisted hydrothermal processing. It was observed that doping favored the orientation of the material along the 040 planes, which presents a better photocatalytic response, in addition to doping modifying the morphology and size of the materials. According to photoluminescence analysis, doping favored charge transfer, which is an essential factor for the photocatalytic properties of the material. The photocatalytic performance was tested with pollutants such as dyes (methylene blue and rhodamine B) and a hormone (17a-ethinylestradiol), showing that doping potentiated the degradation of these pollutants, and the material doping with Pr3+ presented the best result for all the contaminants tested, indicating that it is possible to use these materials for this application.

A novel synergistic effect of TiO2 and ZnO incorporation in PES-based thin-film nanocomposite nanofiltration membrane for treatment of textile wastewater.

A novel synergistic effect of TiO2 and ZnO incorporation in the PES-based thin-film nanocomposite nanofiltration membranes was developed for the treatment of common effluent treatment plant (CETP) textile wastewater. PES@TiO2 membranes were developed by phase inversion via the immersion precipitation method followed by the addition of zinc oxide nanoparticles prepared by the rapid microwave-assisted hydrothermal process via interfacial polymerization. p-Phenylenediamine was used as a monomer for the IP process that was coated on the PES@TiO2 support layer. Various techniques have been applied to characterize the developed thin-film nanocomposite membranes such as Fourier transform infrared (FTIR) microscopy, field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), and contact angle measurement to examine the presence of vibrational modes, surface morphology, the crystal structure of nanoparticles, and hydrophilicity of the membrane, respectively. Membrane properties include porosity, salt rejection, mean pore radius, pure water flux, and industrial effluent rejection efficiency that were studied. The thin-film nanocomposite membrane T5-PES@TiO2(2%)-ZnO(0.3%) was prepared with a combination of 17 wt% PES, 78 wt% DMF, 3 wt% PVP K30, 2% TiO2, 2.5 wt% PPD, 0.3 wt% ZnO, and 1.0 wt% TMC that exhibited high water permeability, porosity, higher industrial effluent rejection, and salt rejection efficiency compared to the neat PES membrane.

Microwave-assisted synthesis of MnO2 nanosorbent for adsorptive removal of Cs(I) and Sr(II) from water solutions.

In this study, a flower-like porous δ-MnO2 nanostructure was synthesized by a microwave-assisted hydrothermal process for adsorptive removal of strontium (Sr(II)) and cesium (Cs(I)) from wastewater. The prepared δ-MnO2 nanosorbent exhibited superior affinity for Sr(II) over Cs(I) in the single-solute system, with partition coefficient (PC) values of 10.2 and 2.3L/g, respectively, at pH 6.0. In the two-solute system, the flower-like δ-MnO2 also adsorbed Sr(II) (PC=3.81L/g) more selectively than Cs(I) (PC 1.15L/g). Further, their adsorption capacities decreased by 12 and 16%, respectively, relative to the single-solute system. In contrast, adsorption of the ions onto δ-MnO2 was affected less sensitively in dual than in single system when changes occurred in environmental variables such as pH (2-8) and ionic strength (1-100mM). Adsorption kinetics, thermodynamics, and isotherm studies demonstrated the pivotal role of the monolayer surface active sites of endothermic δ-MnO2 (e.g., a complexation interaction with Mn-OH). Furthermore, the δ-MnO2 nanosorbent exhibited good regenerability, retaining more than 80% of its adsorption capacity when tested over four reuse cycles. The overall results of this study are expected to help establish strategies to effectively remove metal contaminants from wastewater using a green and low-cost hierarchical nanosorbent.