Methylene Blue Adsorption Capacity Research Articles

Chitosan-polyvinyl alcohol-diatomite hydrogel removes methylene blue from water

Dye pollution in the aquatic environment can harm ecosystems and human health. Here, we developed a new green adsorbent by applying an improved drying process. Diatomite was embedded in a network structure formed between chitosan and polyvinyl alcohol without using any crosslinking agent to prepare chitosan-polyvinyl alcohol-diatomite hydrogel beads through alkali solidification. The beads were tested for removing a cationic dye (methylene blue (MB)) from water. The structure of the adsorbent beads was analysed using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The adsorption capacity was investigated, and the results indicated excellent MB adsorption properties. The adsorbents had a rough surface and high swelling capacity of 66.9 g/g. The maximum MB adsorption capacity was 414.70 mg/g, and the adsorption followed the Freundlich isothermal and quasi-second-order kinetic models. The adsorption was an endothermic spontaneous process governed by both intra-particle and external diffusion processes. The proposed adsorption mechanisms involved hydrogen bonding and electrostatic interactions. These adsorbent beads have considerable application potentials owing to their high adsorption capacity, green composition, and non-polluting nature.

Comparative study of physicochemical properties of geopolymers prepared by four Moroccan natural clays

The present work concerns the development of geopolymer materials based on natural clays rich in kaolinite, muscovite and pyrophyllite. The aim was to study the effect of the nature and fraction of the clay minerals composing the raw sample on the physico-chemical properties of the prepared geopolymers, viz., the matrix geopolymer phase fraction, particle size distribution, density, compressive strength and the adsorption capacity of methylene blue (MB) as a cationic dye model. The raw starting clays, their meta-clay phases calcined at 800 °C, and the prepared geopolymers were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), particle size distribution (PSD) via laser diffraction method, and scanning electron microscopy (SEM). The matrix geopolymer fraction phase in the samples was qualitatively determined by the analysis of the spectra obtained by 27Al and 29Si solid-state NMR. The results showed that kaolinite-rich clay produced more geopolymer than clays with high phase fractions of muscovite or pyrophyllite and low kaolinite. The highest compressive strength was given by the clay that contained 26.7 % of calcite due to formation of calcium silicate hydrate phase. The maximum adsorption capacity of MB was obtained by the samples have a more heterogeneous surface morphology due to presence of unreacted muscovite and/or pyrophyllite in raw starting clay.

Harnessing Prunella vulgaris L. residues for enhanced biosorption of dyes in wastewater

Wastewater containing hazardous dyes, such as methylene blue (MB) and malachite green (MG), poses a significant threat to both the aquatic environment and human health. Therefore, timely treatment of dye wastewater is crucial prior to its discharge into the environment. In this research, Prunella vulgaris L. residues obtained from decoction were selected as a novel raw adsorbent for the efficient removal of methylene blue (MB) and malachite green (MG) from aqueous solutions. The four operational factors, namely adsorbent dosage, initial concentration of target dyes, solution pH, and contact time were optimized using Box-Behnken design of response surface methodology. Under the optimized conditions, the adsorbent demonstrated significantly improved removal efficiency for both MB and MG, achieving 99.62% and 93.29%, respectively. Furthermore, the Freundlich model (Adjusted R2 of MB = 0.9757 and Adjusted R2 of MG = 0.9881) and pseudo-second-order kinetic equation (Adjusted R2 of MB and Adjusted R2 of MG both exceeded 0.9700) were found to accurately describe the adsorption processes of MB and MG, indicating that their adsorption behaviors exhibited favorable multilayer nonuniformity primarily governed by physicochemical interactions. The maximum adsorption capacities of MB and MG in aqueous solutions on the adsorbent were found to be 238.84 and 300.42 mg·g−1, respectively. The adsorption mechanisms of MB and MG on the adsorbent were confirmed through various techniques including SEM, EDS, N2 adsorption-desorption test, Zeta potential class, XPS and FT-IR analysis. These mechanisms include electrostatic adsorption, pore filling, ion exchange, hydrogen bonding, and π-π interaction between the adsorbent and MB/MG. In summary, the residuals of Prunella vulgaris L. after decoction can be considered as a potentially efficient adsorbent material for the removal of MB and MG from aqueous solutions, offering a novel approach to regeneration of Chinese herbal residue.

Boosting methylene blue adsorption capacity of an industrial waste-based geopolymer by depositing graphitic carbon nitride onto its surface: Towards sustainable materials for wastewater treatment

Surface characteristics of a geopolymer (GP) from an industrial waste, red mud (RM), and metakaolin (MK), were tuned by depositing urea-derived graphitic carbon nitride (g-C3N4) onto its surface. Methylene blue (MB) adsorption measurements demonstrated that the resulting g-C3N4/RM-MK-GP offers an excellent MB uptake capacity of 170.9 mg g−1, much higher than those of either the GP or the g-C3N4. Kinetics measurements revealed that chemisorption has an important effect on adsorption. The regenerability of g-C3N4/RM-MK-GP was studied for up to four consecutive cycles. Differences between the adsorption capacities of g-C3N4 and g-C3N4/RM-MK-GP were investigated by combining the power of various characterization tools. Results pointed out that surface functional groups associated with g-C3N4, surface hydroxyl and silanol groups of RM-MK-GP, together with exchangeable charge balancing cations of geopolymeric framework provide a unique structure for g-C3N4/RM-MK-GP. This study presents a versatile route to produce a sustainable, efficient, and cheap adsorbent for wastewater treatment.

Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol, Chitosan, and Activated Carbon or Graphite as Methylene Blue Adsorbents—Comparative Study

Adsorption is a popular technique and has been investigated with many different materials for removing synthetic dyes from textile wastewater. This study compares the methylene blue (MB) adsorption capabilities of surface-modified superparamagnetic iron oxide nanoparticles, (SPION) using polyvinyl alcohol (PVA) and chitosan (CS), combined with two carbon materials, activated carbon (AC) and graphite (GR), respectively. After 9 days, depending on the initial MB loading concentration (0.015 mg/mL, 0.02 mg/mL, and 0.025 mg/mL), the MB adsorption capacities onto SPION/PVA/CS/AC and SPION/PVA/CS/GR were 7.6 ± 0.2–22.4 ± 0.05 and 6.9 ± 0.02–22.4 ± 0.05 mg/g, respectively. The cumulative release percentages of SPION/PVA/CS/AC and SPION/PVA/CS/GR after 30 days were 63.24 ± 8.77%–22.10 ± 2.59% and 91.29 ± 12.35%–24.42 ± 1.40%, respectively. Additionally, both SPION/PVA/CS/AC and SPION/PVA/CS/GR can both fit the Freundlich isotherm model. The adsorption and desorption kinetics can be fitted to the pseudo-second-order linear and zeroth-order models, respectively. At 0.020 mg/mL MB initial loading, out of SPION/PVA/CS/AC, SPION/PVA/CS/GR, and SPION/PVA/CS/GO, SPION/PVA/CS/AC is the most economical adsorbent. Compared to SPION/PVA/AC, SPION/PVA/CS/AC is less economical. Since CS has antimicrobial properties, antimicrobial activities should be investigated to conclude which adsorbent is more promising: SPION/PVA/AC or SPION/PVA/CS/AC.

Impact of inherent calcium in coal on the structure and performance of activated carbon in flue gas activation: The enhanced mechanism of calcite on the methylene blue adsorption

To investigate the correlation and mechanism of inherent calcium species in coal on the preparation and performance of activated carbon (AC) when using flue gas activation. In this study, XCaCO3/AC (X means calcite contents in coal, 0–8 wt.%) was successfully produced by mixing different contents of calcite and demineralized Taixi coal and then using flue gas activation. The textual evolution and methylene blue (MB) removal of AC were conducted by a series of characterizations and tests, and revealed its mechanism. Coal with a high content of calcium could result in a low yield of AC. Calcite could transform into calcium oxide. During AC preparation by flue gas activation, calcium oxide also could react with CO2 and transform into calcium carbonate. Calcite in coal reduced the degree of AC's graphitization. The calcite in coal promotes the increment of CO, COO, and π-π* of AC linearly as the calcite content increases. Due to the excessive catalytic effect of calcite, high-content calcium could result in inferior porosity through promoting the collapse of pore topology. Calcite in coal strengthens the methylene blue (MB) removal capacity of AC. The 5CaCO3/AC possesses the utmost MB adsorption capacity, up to 118.8 mg/g, which is higher by 122.9% than AC of 53.3 mg/g. The various kinetics models were also verified and data was well matched to Pseudo second-order kinetics (R2=0.9165 for AC and R2=9729 for 3CaCO3/AC). Calcite in coal increases the content of CO and π–π* of AC, which strengthens chemical adsorption by functional groups complexation and π–π* stacking. Meanwhile, the existence of calcium species, OH− and CO32− is beneficial for ion exchange and complexation, respectively. Thus, the removal ability of MB by AC is enhanced. The results of this investigation could cast novel light on the high-performance AC design by utilization of high-calcium coal, and further multiple pollutants treatment.

Sugarcane bagasse-derived granular activated carbon hybridized with ash in bio-based alginate/gelatin polymer matrix for methylene blue adsorption

Sugarcane bagasse (SCB) and sugarcane bagasse ash (SCB-ash) are major agricultural residues from sugar processing industries in Thailand. In this study, SCB-derived activated carbon (SCBAC) with the optimum surface area of 489 m2/g was prepared by steam activation at 900 °C for 1 h. Hybrid granular activated carbons (GACs) were successfully developed by mixing SCBAC with bio-based polymers, alginate and gelatin, at the weight ratio of 3:1 for methylene blue (MB) adsorption. SCB-ash, which was additionally mixed in the GACs, could significantly increase compressive strength of the GACs, but decrease their surface areas and MB adsorption efficiencies. An existence of gelatin up to 30 wt% in the polymer matrix of the GACs showed a slight increase in swelling degree and iodine number, but could not enhance bead strength and MB adsorption efficiency due to its relatively lower bulk density and specific surface area. Maximum MB adsorption capacities of the GACs were found at 290–403 mg/g under this study's experimental condition. MB adsorption efficiencies at above 90 % with no deformation of all of the selected SCB hybrid GACs were finally confirmed after seven consecutive adsorption-desorption cycles using a simple regeneration with ethanol.

Fabrication of calix[4]arene/polyurethane for the adsorptive removal of cationic dye from aqueous solutions.

Calix[4]arene/polyurethane (C4PU) has been synthesized and characterized as an alternative adsorbent for the adsorption of methylene blue (MB) and malachite green (MG) dyes from the aqueous solution. C4PU was synthesized by reacting p-tert-butyl calix[4]arene with hexamethylene diisocyanate (HMDI) as the cross-linking agent. Different polymer ratios were synthesized, and C4PU-4 shows better adsorption than other ratios. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis, and point of zero charges (pHPZC). The isotherms and kinetics of the adsorption of MB and MG were studied under a range of experimental conditions, including pH, adsorbent dosage, initial dye concentration, and contact time. The adsorption was determined by the adsorption percentage of MB and MG dyes from the solution. The Langmuir isotherm model best describes the adsorption process for both dyes, and it follows a pseudo-second-order kinetic model, with the maximum adsorption capacity (qmax) of MB and MG, respectively, was found to be 1.991mg·g-1 and 2.240mg·g-1.

Response surface methodology for optimizing methylene blue dye removal by mesoporous activated carbon derived from renewable woody Bambusoideae waste

In this study, the focus was on utilizing tropical plant biomass waste, specifically bamboo (BB), as a sustainable precursor for the production of activated carbon (BBAC) via pyrolysis-induced K2CO3 activation. The potential application of BBAC as an effective adsorbent for the removal of methylene blue (MB) dye from aqueous solutions was investigated. Response surface methodology (RSM) was employed to evaluate key adsorption characteristics, which included BBAC dosage (A: 0.02–0.08 g/L), pH (B: 4–10), and time (C: 2–8 min). The adsorption isotherm analysis revealed that the adsorption of MB followed the Freundlich model. Moreover, the kinetic data were well-described by the pseudo-second-order model, suggesting the role of a chemisorption process. The BBAC demonstrated a notable MB adsorption capacity of 195.8 mg/g, highlighting its effectiveness as an adsorbent. Multiple mechanisms were identified as controlling factors in MB adsorption by BBAC, including electrostatic forces, π–π stacking, and H-bonding interactions. The findings of this study indicate that BBAC derived from bamboo has the potential to be a promising adsorbent for the treatment of wastewater containing organic dyes. The employment of sustainable precursors like bamboo for activated carbon production contributes to environmentally friendly waste management practices and offers a solution for the remediation of dye-contaminated wastewater.

A novel Fe-containing carbon foam with hierarchical porous structure for efficient removal of organic dyes

A novel Fe-containing carbon foam (Fe-CF) was achieved with a hierarchical porous structure by carbonization of nano‑magnesium oxide/epoxy resin mixture followed by Fe(NO3)3 activation. The structures and properties of as-prepared Fe-CF were characterized via XRD, compression strength test, FESEM, TEM, BET, Raman and XPS, meanwhile the effects of adsorption conditions on the removal performance of Congo red (CR), Malachite green (MG) and Methylene blue (MB) by the Fe-CF are investigated through batch adsorption experiments. Results show that the Fe-CF obtained at 1000 °C possesses a fluffy and porous structure without obvious collapse and closure, and the iron oxide particles are evenly distributed on its surface, which endows it with high adsorption capacities for CR (1263.36 mg g−1), MG (679.84 mg g−1) and MB (483.66 mg g−1) at the optimum conditions, respectively. Furthermore, the adsorption process can be depicted well by the Langmuir and pseudo-second-order models, and the thermodynamic analysis results reflect that the adsorption processes are thermodynamically feasible and spontaneous. More importantly, the prepared adsorbent retains relatively high adsorption ability and stability even after five regeneration cycles.

Production and characterization of activated carbon derived from orange peel for the adsorption of methylene blue dye

Activated carbon was produced from orange peel using H2SO4 and ZnCl2 as activating agents at a temperature of 400 oC. The impregnation was done in 1:1 (wt/v). FTIR analysis of the precursor and activated carbon shows different functional groups present in the precursor and activated carbon. The FTIR spectral also shows shifts in bands and changes in wave number between the precursor and activated carbon indicating chemical transformation during activation and carbonization. SEM analysis was used to study the internal structure and pores development of the activated carbon. The methylene blue adsorption capacity of the activated carbon was determined using standard methods. Langmuir and Freundlich adsorption isotherms were employed in determining the adsorption process and Pseudo first-order and Pseudo secondorder kinetics were employed in determining the rate of adsorption by the adsorbents.

Activation temperature dependence of Adonidia merrillii palm seed porous activated carbons textural properties. Adsorption of methylene blue in batch systems

From a char of Palm seed (CSP), activated carbon at 973, 1073, and 1173 K was obtained (CASPs). These temperatures developed textural properties to favor the adsorptive properties. The CASPs percentage of burning decreased with the increase of the activation temperature from 76 to 26%. These products were obtained with a CO2 flow (as activating gas) and a short time of activation. The CASPs were characterized by mercury porosimetry, adsorption of N2, CO2, and methylene blue at 77, 273, and 298 K, respectively. Wide supermicropores were obtained for CASP1173 and narrow mesoporosity was achieved for CASP973 and CASP11073 (1.4–2.0 nm and 2.0–5.0 nm, respectively). Mercury porosimetry determined that the activated carbons have mesopores with diameters smaller than 50 nm and macropores with diameters greater than 50 nm. The use of Dubinin and Langmuir models showed that the adsorption occurred in the larger diameter micropores and smaller diameter mesopores of the highest and shortest diameters (above 3.85 mmol/g). The activated carbon at 973 K showed a higher methylene blue adsorption capacity (181.03 mg/g). The MB adsorption was determined by the diameters of the adsorbent pores. For this reason, a batch adsorption system to remove this contaminant was proposed.

Photo-induced adsorption-desorption behavior of methylene blue on CA-BMO under visible light irradiation.

In this work, the modification of Bi2MoO6 with critic acid (CA-BMO) to achieve enhanced adsorption of methylene blue (MB) solution in dark and desorption under visible light irradiation was reported. The as-prepared materials were synthesized by a hydrothermal method and characterized via SEM, FT-IR, XRD, and XPS techniques. Only 16.5% of 10mg L-1MB was removed within 10min by using 0.5g L-1 Bi2MoO6, while 92.9% removal of MB could be achieved by using 0.5g L-1 CA-BMO, which enhanced the adsorption removal by a factor of 4.6. The adsorption capacity for MB was 18.9mgg-1. Desorption efficiency of MB was only observed in CA-BMO system, and it depends on the wavelength of the light source, pH, and the presence of metal ions. Characterization results suggested that carboxyl groups, which were modified onto the surface of Bi2MoO6, could serve as adsorption sites for MB, and the connections were damaged under light, thus leading to the desorption of MB from the surface of the CA-BMO. This study provides a novel reagent-free desorption strategy for dye recovery without secondary pollution, which facilitates the development and application of Bi-based adsorbent for dye-containing wastewater treatment.

Antibacterial mechanism of Xiuyan jade mineral waste as a natural inorganic antibacterial agent

The Xiuyan jade waste exhibits prominent antibacterial properties after mechanical activation; these properties can be further optimized through low-temperature annealing. To elucidate its antibacterial mechanism, analysis methods involving metal-ion leaching monitoring and zeta potential analysis were used. Although the activated waste cannot be easily dissolved in water, Mg2+ and Ca2+ ions precipitated when the waste particles were dispersed in water. The particle surface showed different degrees of electronegativity, which could be the main reason for the antibacterial properties of the material. This study proved the importance of the surface electrical properties of activated waste particles on their properties by observing their adsorption capacity for methylene blue. At the annealing temperature of 270 °C, the Xiuyan jade waste exhibited the highest electronegativity and optimal antibacterial properties as well as the adsorption rate of methylene blue, verifying the significance of electronegativity of activated mineral waste powders on the antibacterial mechanism.

Raw Materials Used in Traditional Pottery from Northern Morocco: Possible Alternative Material for a Sustainable Future in the Fran Ali Area

AbstractThe colluvium and saprolite deposits in the Fran Ali area (Oued Laou, northern Morocco) constitute the main source of raw materials used in traditional pottery. These materials are becoming scarce, however, so alternative materials with the same characteristics are needed; this would ensure the sustainability of pottery activities in the area. The objective of the present study was to examine ten representative samples of clayey materials extracted from the Fran Ali area, i.e. the Ikhadimene, Dar Haddoune, Ihadounene, Aqqbat Ajjoua, and Isalahene sites. The geological materials consist mainly of grayish to brownish phyllites, thin layers of yellowish clay, thicker intervals of reddish-yellow soils ranging in depth from 1 to 4 m, and reddish colluvium soils. The physical properties of these materials were determined using semi-wet sieving and Atterberg limit tests, while chemical, mineralogical, and thermal properties were obtained from the methylene blue test (MBT), the calcimetry test, X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), and thermogravimetric and differential thermal (TGA/DTGA) analysis. The results suggest that the soils contain 21–35% clay, 28–34% silt, and 37–52% sand. They are moderately plastic, with methylene blue adsorption capacities ranging from 3 to 7% and minimal CaCO3 carbonate contents (1–4%). Samples are dominated by SiO2 (51–57%), Al2O3 (17–21%), and Fe2O3 (8–10%). Mineralogically, they are composed of illite (19–27%), chlorite (0–22%), kaolinite (5–9%), and quartz (29–32%). Thermal analysis showed a relatively large mass loss of ~10%. The samples are deemed to be moderately plastic. The results indicate that this raw material is acceptable for pottery fabrication, given the small proportion of irregular interlayer content and its average geotechnical properties. In addition, extraction of the colluvium material is not sustainable because of the relative scarcity of the material. Given the mineralogical similarity between the weathered layers (colluvium) and their parent rock (shales), the present results suggest that the latter is a suitable alternative to the former.

Zn-modified biochar preparation from solvent free in-situ pyrolysis and its removal of methylene blue

In this study, Zn-modified biochar obtained through of Jerusalem artichokes straw with zinc carbonate was used to explore its effect on the adsorption of methylene blue. The physical and chemical properties of Zn-modified biochar were investigated using a variety of characterization, including SEM, BET, FT-IR, Raman, XRD, and XPS. Compared with the original biochar, the specific surface area (1037.17 m2·g−1) of Zn-modified biochar pyrolysis at 800 °C (Zn-BC 800) increased approximately 22 times. The adsorption of methylene blue with Zn-BC 800 could be more accurately illustrated by the pseudo-second-order kinetic model. The fitting results of adsorption isotherms showed that the Langmuir model could better suit the adsorption process at three different temperatures. At 318 K, Zn-BC 800 had a maximum adsorption capacity for methylene blue of 477.13 mg·g−1. According to the thermodynamic analysis, the process was a spontaneous endothermic reaction, and increasing the reaction temperature was beneficial to the reaction. Hydrogen bond and π-π interaction were the main mechanism of adsorption of MB by Zn-BC 800, which was determined by FTIR and XPS analysis. Zn-BC 800 still had a high adsorption effect on methylene blue after 5 cycles, indicating that the composite was a highly efficient cationic dye adsorbent, which could effectively remove dyes from wastewater.

Preparation of magnetic lignin-based adsorbents and its adsorption properties for dyes

In this study, the renewable magnetic lignin-based material with good properties and environmental friendliness was successfully prepared and used for the treatment of wastewater. Lignin nanospheres (LNS) were prepared from stearyl chloride esterified alkali lignin via self-assembly in the mixture and raspberry-like magnetic lignin microspheres (Fe3O4@SiO2-LNS) was successfully prepared by grafting LNS onto the surface of Fe3O4@SiO2 particles by chemical crosslinking, then was used as absorbent for Methylene blue (MB) and Rhodamine B (RhB) dyes. The results indicated that the Fe3O4@SiO2-LNS had excellent adsorptivity in alkaline solution, and the maximum adsorption capacities for MB and RhB were 258.40 mg·g-1 and 124.38 mg·g-1 , respectively. The Fe3O4@SiO2-LNS adsorbent can be recycled due to its good magnetism and the regeneration efficiency is over 85% after three cycles. Therefore, the prepared magnetic lignin-based adsorbent is a lowcost, high-efficiency and reusable adsorbent for wastewater treatment.

Trithiocyanurate-functionalized hydrochar for effectively removing methylene blue and Pb (II) cationic pollutants

Functionalization can change the physicochemical properties of hydrochar and improve its ability to adsorb pollutants. Herein, a trithiocyanurate-functionalized hydrochar (TTHC) was obtained from acylation of chloroacetyl chloride and hydrochar and modification with trithiocyanuric acid in alkaline conditions. TTHC can efficiently remove cationic methylene blue (MB) and Pb(II) from wastewater. The removal can be expressed with pseudo-second-order kinetic and Langmuir models. The MB and Pb(II) removed uptakes by TTHC at 298 K exceeded 909.9 and 182.8 mg g−1 respectively, and the removal rates reached 90% and 98% within 120 min respectively. Characterizations show TTHC is functionalized with trithiocyanurate, and rich in thiolate and aromaticity, and tends to adsorb MB/Pb(II) via multiple adsorption mechanisms. After five sorption-desorption regeneration cycles, TTHC maintained 80% and 99% adsorption capacities for MB and Pb(II) respectively. Therefore, TTHC is a promising efficient sorbent for removing MB and Pb(II) from effluents.

Waste treat waste: Alginate calcium versus alginate acid gels in upcycling waste cotton linter as composite biosorbent

Transforming waste materials into biosorbent offers a valuable solution for cost-effective water decontamination while simultaneously promoting waste upcycling. This study focused on the gelation of alginate calcium (AC) and alginate acid (AA) in recycling waste cotton linters (WCL) to create composite hydrogels for dye removal. Both hydrogel systems effectively incorporate WCL, displaying an impressive 80 wt% WCL entrapping capacity in the composite hydrogels. The presence of WCL leads to a fascinating volume expansion phenomenon, particularly noticeable in AC composite systems after freeze-drying. Additionally, the composite hydrogels demonstrate efficient adsorption of methylene blue (MB), ranging from 5 to 22 mg/g in MB dye solution (30 mg L−1), and exhibit good compatibility with various adsorption kinetic models. However, AC composite systems outperform AA composite systems and display higher MB adsorption capacity, faster adsorption rate, and more consistent performance. Mechanistic studies reveal that electrostatic forces contribute to volume expansion and dye adsorption, while the denser crosslinking structure and more abundant carboxylate groups in the AC composite system contribute to its superior performance. Our current study not only establishes the criteria for selecting proper alginate system as bio-composite hydrogel matrices, but also provides a sustainable “waste treat waste” upcycling strategy.

Sargassum macro-algae-derived activated bio-char as a sustainable and cost-effective adsorbent for cationic dyes: A joint experimental and DFT study

Activated bio-char prepared from the pyrolysis and CO2-based physical activation of Sargassum macro-algae was developed as a sustainable and cost-effective adsorbent for malachite green (MG) and methylene blue (MB) adsorption. Prepared activated bio-char was characterized with CHNS, FESEM, Raman, FT-IR and N2 adsorption/desorption methods. Langmuir isotherm and pseudo second order kinetics model best fitted equilibrium and kinetics data. The maximum adsorption capacity for MG and MB were 500 and 204.8 mg/g. The effect of solution pH and temperature on adsorption efficiency was studied and discussed. Acid treatment easily regenerated the adsorbent. After 5 cycles, the MB and MG adsorption efficiency reached 89 % and 78 %, respectively. A Density Functional Theory (DFT) calculation showed that pH-N-(CH3)2 of MB was strongly attracted to the -COOH functional groups in activated bio-char. For MG, the order of preferred interactions between the ph-N-(CH3)2 groups and the functional groups of adsorbent was -CONH2>-COOH>-COH.