Cost effective porous areca nut carbon nanospheres for adsorptive removal of dyes and their binary mixtures

Novel porous nanospheres from areca nuts (ACNPs) were synthesized via one-step pyrolysis without the use of any chemical treatment and the materials were used as adsorbents for the removal of cationic methylene blue (MB) and anionic methyl orange (MO) as well as their binary mixtures. Around, 6-7 tonnes of areca nut biowaste is generated every year which are then burnt due to their slow rate of decomposition resulting in higher carbon footprints. Biosorbents are generally a preferable alternative for dye adsorption but involve chemical modification for surface enhancement and complex sample treatment. In this work, ACNPs, were investigated for their efficiency in the raw form and were characterized by SEM, EDS, FTIR, XRD, and BET techniques before and after subjecting to the dye adsorption studies. The BET analysis of the adsorbents showed a high specific surface area of 693.8 m²/g when prepared at 1000 °C, while the N₂ adsorption-desorption plot showed type-IV isotherm, suggesting the microporous nature of the carbon matrix. Batch equilibrium studies showed the removal efficiency of >95% for both the dyes and their binary mixtures under the optimum conditions of 0.15 g/L dosage, 10 μM concentration and contact time of 70 min. Due to the synergistic effects of the binary dyes, higher removal efficiency of MB compared to MO was observed in the binary mixture. Adsorption results were tested using Langmuir, Freundlich, Temkin, Redlich-Peterson, and Elovich isotherms to assess the best fit of the models. The q_m value of MB was found to be 97.37 mg/g, while that of MO was 71.22 mg/g which is higher compared to individual dye components having lower values of 86.12 mg/g and 50.35 mg/g, respectively. Extended Langmuir and Jain and Snoeyink isotherms were used for binary data interpretation. The kinetic results showed good agreement with the Pseudo-second order equation, indicating internal diffusion. The possible mechanism involved electrostatic and ᴨ-ᴨ interactions between the dye molecules and ACNPs. This approach is comprehensible and cost effective and can be utilized for dye removal in textile industries.

Total removal of amoxicillin from water using magnetic core nanoparticles functionalized with silver

Framed in the problem of emerging pollutants, in this work we introduce a novel procedure for the total removal of amoxicillin from water samples using magnetic nanoparticles functionalized with nanometric silver (Fe₃O₄@AgNPs). Experimental conditions such as pH, contact time, temperature, as well as adsorbate and adsorbent doses have been studied to achieve the total adsorption for different concentrations of amoxicillin in water. Particularly, for concentrations 10 and 100 mg L^-1, a maximum removal efficiency of 100% was reached at room temperature and pH = 7 after 15 min of contact time between adsorbent and water samples under gentle shaking. The doses of adsorbent employed to remove 10 and 100 mg L^-1 of amoxicillin were 100 and 500 μL, respectively. Characterization of the adsorbent surfaces was performed by Scanning and Transmission Electron Microscopy, Energy Dispersive X-ray Spectroscopy, BET analysis and Fourier-transform infrared spectroscopy. Recycling studies were carried out employing 500 μL of NaOH solution 1 M during 15 min in order to explore desorption and reuse of the adsorbent, showing that Fe₃O₄@AgNPs remains unaltered and can be used for two more additionally adsorption cycles, exhibiting 93% adsorption efficiency after the third regeneration. The characterization of equilibrium isotherms and thermodynamics reveal a Langmuir-type endothermic chemisorption.

Synthesis and application of graphene oxide as a nanoadsorbent to remove Cd (II) and Pb (II) from water: adsorption equilibrium, kinetics, and regeneration

In this work, graphene oxide (GO) was synthesized by the modified Hummers method. The nanomaterial was characterized by FTIR and Raman spectroscopy, SEM, and pH at the point of zero charge. GO exhibited typical characteristics of graphene-based materials, indicating that graphite oxidation and exfoliation occurred successfully. Cd (II) and Pb (II) adsorption onto GO was carried out in batch systems, in which the effect of adsorbent dosage, contact time, and initial adsorbate concentration were evaluated. Langmuir, Freundlich, and Sips isotherm models, as well as pseudo order models and Elovich kinetic equation were applied to adsorption experimental data. Results indicated that increasing adsorbent mass, the removal efficiency of Cd (II) and Pb (II) increased. Freundlich isotherm better described Pb (II) adsorption (R² = 0.96), while Cd (II) isotherm showed linear behavior. From the Akaike's AIC parameter, kinetic data were satisfactorily described by pseudo-first order (Cd (II)) and pseudo-n order (Pb (II)) models. GO was successfully subjected to five regeneration cycles, maintaining high efficiency (> 90%) in all cycles. GO showed high potential for the adsorption of Cd (II) and Pb (II) from aqueous solution, due to its high adsorption capacity, rapid Cd (II) and Pb (II) intakes, and great regeneration performance.

Taguchi optimization design of diameter-controlled synthesis of multi walled carbon nanotubes for the adsorption of Pb(II) and Ni(II) from chemical industry wastewater

Herein, Taguchi L₉ orthogonal array was used for the first time to optimize synthesis of diameter-controlled multi walled carbon nanotubes (MWCNTs). The nanoadsorbents, MWCNTs_5-15 nm and MWCNTs_16-25 nm were applied for Pb(II) and Ni(II) ion removal from paint, battery and electroplating wastewater. The results indicated successful synthesis of MWCNTs with diameter distribution ranges of 5-15 nm and 16-25 nm. The synthetized smaller diameter MWCNTs_5-15 nm revealed higher Brunauer-Emett-Teller (BET) surface area of 1306 ± 5 m²/g compared to larger diameter MWCNTs_16-25 nmwith the surface area of 1245 ± 4 m²/g. They demonstrated excellent adsorption of Pb(II) and Ni(II) ions within the permissible concentration proposed by WHO at pH, contact time, adsorbent dosage and temperature of 5, 60 min, 30 mg/L and 50 °C, respectively. Particularly, MWCNTs_5-15 nm possessed high adsorption capacity of 215.38 ± 0.03 mg/g for Pb(II) and 230.78 ± 0.01 mg/g for Ni(II). Again, the maximum adsorption capacity of 201.35 ± 0.02 and 206.40 ± 0.02 mg/g was achieved for Pb(II) and Ni(II) using MWCNTs_16-25 nm. All in all, the adsorption capacity of the nanoadsorbents at the investigated diameter range showed higher efficiency compared to other materials for heavy metals elimination from chemical industrial wastewater.

Application of cellulose nanocrystals prepared from agricultural wastes for synthesis of starch-based hydrogel nanocomposites: Efficient and selective nanoadsorbent for removal of cationic dyes from water

A novel and bio-based hydrogel nanocomposite were developed using reinforcement of starch grafted copolymers of 2-acrylamido-2methyl propane sulfonate and acrylic acid (starch-g-(AMPS-co-AA)) hydrogel with magnetite-functionalized cellulose nanocrystals (MCNCs). The MCNCs-hydrogel was utilized as a proficient and environmentally benign nanoadsorbent for removal of cationic dyes with great capacity and selectivity. Sugar-beet pulp (SBP) was exploited for CNCs production through acid hydrolysis of enzymatic-mediated SBP. Fe₃O₄ nanoparticles were anchored on CNCs to synthesize MCNCs as the nanofiller of MCNCs/starch-g-(AMPS-co-AA) hydrogel. The synthesis of CNCs, MCNCs and hydrogel nanocomposite were confirmed using FESEM, FTIR, VSM and TGA analyses. Hydrogel nanocomposite showed excellent and reusable capacity for specific adsorption of cationic dyes. The effects of nanoadsorbent dosage, time, pH, dye initial concentration, and temperature on the adsorption were scrutinized for two model cationic dyes (crystal violet (CV) and methylene blue (MB). Adsorption capacities for CV and MB were 2500.0 mg/g and 1428.6 mg/g, respectively.

Proficient dye removal from water using biogenic silver nanoparticles prepared through solid-state synthetic route

An environmentally benign, one-pot and highly scalable method was presented to produce biogenic silver nanoparticles (Ag NPs) using the solid-state synthetic route. Four plant-derived candidate bio-reductants (i.e., Datura stramonium, Papaver orientale, Mentha piperita, and Cannabis sativa) were investigated to compare the efficiency of solid-state route and typical solution method. M. piperita was selected as the best plant resource to produce totally pure and uniform Ag NPs (average diameter of 15 nm) without any aggregation. The purity and size of biogenic Ag NPs, were tailored by adjusting the M. piperita leaf powder/silver nitrate weight ratio and temperature. The as-synthesized Ag NPs were effectively utilized as an eco-friendly nanoadsorbent in water remediation to remove a model dye (i.e., crystal violet). The key factors affecting on the sorption process (i.e., nanoadsorbent dosage, temperature, pH, dye initial concentration, and shaking time) were investigated. The pseudo-second-order kinetic model was well fitted to the sorption process and at the optimum sorption conditions, based on the Langmuir model, the adsorption capacity was found to be 704.7 mg/g. The current, cost effective and feasible method could be considered as an applicable strategy to produce green, reusable and proficient Ag NPs as nanoadsorbents for removal of dyes from contaminated water.

Removal of Pb (II) from aqueous solution using nanoadsorbent of Oryza sativa husk: Isotherm, kinetic and thermodynamic studies

This research focus on the removal of Pb (II) ions from aqueous solution by adsorption process using nanoadsorbent developed from agricultural waste Oryza sativa husk (OSH). Surface morphology of nanoadsorbent was analyzed by FE-SEM, elemental composition by EDX and size by AFM. Attachment of functional groups on nanoadsorbent was determined by FTIR. The effect of pH, dose, contact time, initial concentration and temperature were investigated. Optimum adsorption of lead at pH 8, contact time 70 min at 60 °C temperature with 0.6 g/50 mL nanoadsorbent dose obeyed pseudo second order kinetic model with R² 0.996. Pb (II) adsorption was analyzed by Freundlich, Langmuir and Temkin models. Freundlich isotherm model with correlation coefficient R² 0.999 was best fitted. Thermodynamic parameters anticipated the adsorption process to be endothermic and spontaneous. Post adsorption elution was carried out successfully. Results demonstrate that OSH is a low cost and eco-friendly choice for Pb (II) remediation.

Robust photoactive nanoadsorbents with antibacterial activity for the removal of dyes

ZnO nanostructures (NS)/guar gum (GG) nanocomposites have been successfully synthesized and tested as sorbents for photodegradation, adsorption and antimicrobial activity for dye removal. The addition of ZnO improves the thermal stability of GG based on the ratio of the oxygen in the OH form and the total oxygen in the samples as indicated via XPS and FTIR analyses. Among all tested composites, the ZnO NPs/GG nanocomposite showed the highest photocatalytic activity and hence used in extended adsorption and degradation studies against the anionic dye reactive red (RR195) and the cationic dye Rhodamine B (RhB). The adsorption mechanism and kinetics were studied in details. The ZnO NPs/GG nanocomposite showed quite high removal efficiency for both dyes reaching about 96 degradation percent of the initial dye concentration as well as a high adsorption capacity reaching 70 mg g^-1. The adsorption of both dyes on ZnO NPs/GG was found to obey the Freundlich adsorption model with pseudo-second-order kinetics. The antibacterial assay showed an enhanced antibacterial effect of ZnO/GG against E-Coli/TOP10 (PTA 10989) strain compared to pristine ZnO or pure guar gum. The obtained results were proved to be of high significance based on the statistical analysis using one-way ANOVA followed by Tukey's analysis.

Study of arsenic (III) removal by monolayer protected silver nanoadsorbent and its execution on prokaryotic system

This work deals with the removal of arsenic by nanoadsorbent from aqueous environment that is subsequently applied to the biological system for the evaluation of its efficiency. We started our aspiration by the modification of carboxylate functionalized silver nanoparticle (nanoadsorbent) fabrication process. Batch mode arsenic uptake study by the nanoadsorbent was conducted considering several altering parameters and the reactants in addition to products were evaluated by several analytical techniques for the interpretation of the interaction mechanism. It was found nanoadsorbent, Ag@MSA is an efficient system for the exclusion of arsenic (III) from the aqueous system and due to the alteration in the ratio of silver content and protective agent, the characteristic profile of silver nanoparticles with an average diameter of 15 nm also became changed in respect of reported results. Here the low pH range (4-6) favors the interaction between nanoparticle and arsenic and it was found that the interaction was chemical in nature through adsorption or complex formation with surface carboxylate groups of the protecting agent (MSA). Following the interaction, a successful removal of arsenic (III) was achieved at a percentage of 94.16 with an initial concentration of 45 mg/L and equilibrium time of 60 min. Hence nanoparticles were executed against the toxic effect of arsenic in E. coli, an important gut microbe of higher animals, for the restoration of bacterial growth in arsenic pre-removed media. In this context the validation of this removal efficiency against arsenic induced toxicity was proved through several morphological studies, degree of oxidative damages and other biochemical attributes.

Applications of three-dimensional graphenes for preconcentration, extraction, and sorption of chemical species: a review

This review (with 115 refs) summarizes applications of 3-dimensional graphene (3DGs) and its derivatives in the fields of preconcentration, extraction, and sorption. Following an introduction into the field (including a definition of the materials treated here), the properties and synthetic strategies for 3DGs are described. The next section covers applications of 3DG-based adsorbents in solid phase extraction of organic species including drugs, phthalate esters, chlorophenols, aflatoxins, insecticides, and pesticides. Another section treats applications of 3DGs in solid phase microextraction of species such as polycyclic aromatic hydrocarbons, alcohols, and pesticides. We also describe how the efficiency of assays may be improved by using these materials as a sorbent. A final section covers conclusions and perspectives. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.Tiff file of graphical abstract was attached. Schematic presentation of synthesis of three-dimensional graphene (3DG) from two-dimensional graphene (2DG) with self-assembly, template-assisted and direct deposition methods. Application of 3DG-based nanoadsorbents in direct immersion-solid phase microextraction (DI-SPME), headspace-SPME (HS-SPME), magnetic-solid phase extraction (Magnetic-SPE), dispersive-SPE, and magnetic sheet-SPE.

Titanium oxide-bacterial cellulose bioadsorbent for the removal of lead ions from aqueous solution

In the current study, nanocomposites of bacterial cellulose (BC) and amorphous TiO₂ were prepared and characterized. The nanocomposites were evaluated as adsorbent for the removal of lead (Pb) from aqueous solution. The different reactions conditions such as pH, equilibrium time, temperature, adsorbent dose and possible recycling of adsorbent were studied. The nanocomposites were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The characterization results confirmed the formation of nanocomposites. Moreover, BC modified with 3 wt% TiO₂ showed best results for the removal of Pb ions from aqueous solution. TiO₂-BC nanocomposites remove Pb in concentration of 100 mg/L with removal efficiency above 90% in 120 min at pH 7 and room temperature. The adsorbent was recycled, and no profound decrease of efficiency was observed till three cycles of use. Desorption studies were also carried out for the reusability of the adsorbent. The adsorbent was found efficient, stable and reusable for the removal of lead in environmental water samples.

Facile synthesis of smartaminosilane modified- SnO2/porous silica nanocomposite for high efficiency removal of lead ions and bacterial inactivation

The aim of the present study is to synthesize a new and proficient nanoadsorbent for rapid removal of heavy metals and disinfection of microorganisms. The proposed nanoadsorbent was fabricated using SnO₂ nanoparticles as the core, coated with mesoporous silica and further modified with 3-Aminopropyl triethoxysilane to render SnO₂/PSi/NH₂ nanocomposite. The nanocomposite was characterized using Fourier Transform Infrared (FTIR), X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Nitrogen adsorption-desorption analysis. The potential of the resultant SnO₂/PSi/NH₂ nanocomposite for the convenient removal of Lead ions in a batch systems was investigated as a function of solution pH, contact time, adsorbent dosage, temperature and metal ion concentration. The adsorption behavior was in good agreement with Sips and Langmuir isotherm models. The maximum adsorption capacity of SnO₂/PSi/NH₂ was 653.62 mg g^-1. Furthermore, the desorption experiments demonstrated that the proposed nanocomposite could be used frequently for at least three consecutive cycles with minor losses in adsorption performance. The bacterial inactivation ability of SnO₂/PSi/NH₂ toward E-Coli and S. aureus bacteria was also evaluated using disk diffusion and linear cultivation tests, according to which the SnO₂/PSi/NH₂ nanocomposite possessed exceptional disinfection ability toward both bacteria, specifically S. aureus.

A nanocomposite consisting of silica-coated magnetite and phenyl-functionalized graphene oxide for extraction of polycyclic aromatic hydrocarbon from aqueous matrices

In this study, graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe₃O₄@SiO₂@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The resulting microspheres (Fe₃O₄@SiO₂@GO-PEA) were characterized by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), CHNS elemental analysis, and vibrating sample magnetometry (VSM) techniques. The adsorbent possesses the magnetic properties of Fe₃O₄ nanoparticles that allow them easily to be separated by an external magnetic field. They also have the high specific surface area of graphene oxide which improves adsorption capacity. Desorption conditions, extraction time, amount of adsorbent, salt concentration, and pH were investigated and optimized. Following desorption, the PAHs were quantified by gas chromatography with flame ionization detection (GC-FID). The limits of detection (at an S/N ratio of 3) were achieved from 0.005 to 0.1μg/L with regression coefficients (R²) higher than 0.9954. The relative standard deviations (RSDs) were below 5.8% (intraday) and 6.2% (inter-day), respectively. The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7% and 106.7% (with RSDs of 1.6% to 8.4%, for n=3). The results indicated that the Fe₃O₄@SiO₂@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.

Novel application of nanozeolite for radioactive cesium removal from high-salt wastewater

Finding a striking peculiarity of nanomaterials and evaluating its feasibility for practical use are interesting topics of research. We investigated the application of nanozeolite's outstanding reactivity for a rapid and effective method for radioactive cesium removal in the wastewater generated from nuclear power plant accident, as a new concept. Extremely fast removal of cesium, even without stirring, was achieved by the nanozeolite at efficiencies never observed with bulk materials. The nanozeolite reached an adsorption equilibrium state within 1 min. Cesium adsorption by nanozeolite was demonstrated at reaction rates of orders of magnitude higher than that of larger zeolite phases. This observation was strongly supported by the positive correlation between the rate constant ratio (k2,bulk/k2,nano) and the initial Cs concentrations with a correlation coefficient (R(2)) of 0.99. A potential drawback of a nanoadsorbent is the difficulty of particle settling and separation because of its high dispersivity in solution. However, our results also demonstrated that the nanozeolite could be easily precipitated from the high-salt solution with ferric flocculant. The flocculation index reached a steady state within 10 min. A series of our experimental results met the goal of rapid processing in the case of emergency by applying the well-suited nanozeolite adsorption and flocculation.

Equilibrium, kinetic and thermodynamic study of cesium adsorption onto nanocrystalline mordenite from high-salt solution

In this study, the equilibrium, kinetics and thermodynamics of cesium adsorption by nanocrystalline mordenite were investigated under cesium contamination with high-salt solution, simulating the case of an operation and decommissioning of nuclear facilities or an accident during the processes. The adsorption rate constants were determined using a pseudo second-order kinetic model. The kinetic results strongly demonstrated that the cesium adsorption rate of nano mordenite is extremely fast, even in a high-salt solution, and much faster than that of micro mordenite. In the equilibrium study, the Langmuir isotherm model fit the cesium adsorption data of nano mordenite better than the Freundlich model, which suggests that cesium adsorption onto nano mordenite is a monolayer homogeneous adsorption process. The obtained thermodynamic parameters indicated that the adsorption involved a very stable chemical reaction. In particular, the combination of rapid particle dispersion and rapid cesium adsorption of the nano mordenite in the solution resulted in a rapid and effective process for cesium removal without stirring, which may offer great advantages for low energy consumption and simple operation.

Preparation of functionalized graphene oxide and its application as a nanoadsorbent for Hg(2+) removal from aqueous solution

A poly(allyl acetoacetate)-grafted graphene oxide (GO-GAA) was successfully synthesized using Hummer's method by divinyl sulfone modification and allyl acetoacetate polymerizaton. This novel functionalized graphene oxide was characterized thoroughly by FTIR, XRD, FE-SEM, TEM, and TG-DT analyses. GO-GAA was then employed as an adsorbent for Hg(2+) removal from aqueous solutions. It exhibited higher adsorption capacity with regard to the pristine graphene oxide because of its effective functionalities, especially the dicarbonyl groups which are significant chelating agents. The effects of pH, temperature, and contact time on Hg(2+) adsorption were also investigated. The optimum Hg(2+) adsorption was obtained at pH 4 and T = 20-30 °C. The adsorption isotherm and kinetics were found to follow the Langmuir and pseudo-second-order models, respectively, with a correlation coefficient of 0.99 for both. The calculated maximum adsorption capacity of the adsorbent was 282.7 mg Hg(2+) per unit mass of GO-GAA, which is much more than 56 mg/g of that obtained for GO. The results showed that adsorption reaches up to 95 % of its maximum in less than 2 min. The synthesized GO-GAA as a novel and efficient adsorbent has been regenerated by HNO3 and reused. It retained its performance for Hg(2+) removal for several times and a less than 5 % decrease in removal efficiency was observed after four cycles of adsorption-desorption.

Preparation and application of oyster shell supported zero valent nano scale iron for removal of natural organic matter from aqueous solutions

Background

In this Research, oyster shell supported zero valent iron nanoparticles were prepared and applied for the removal of natural organic matters (NOMs) from aqueous solutions under different experimental conditions.

Methods

The nanoadsorbents prepared by wet impregnation method, then characterized using Scanning Electron Microscopy, Energy Dispersive Spectroscopy, X-Ray Fluorescence and BET analysis. Adsorption test was done in a batch reactor and the effects of different parameters such as initial adsorbate concentration, adsorbent dose, adsorption kinetic, pH, and temperature on removal of NOMs (humic acid as the indicator) were studied.

Results

Results showed that particle size of nanoadsorbent was in the range of 60-83 nm, and surface area and micropore volume as 16.85 m²/g and 0.021 m³/g, respectively; the main elements of adsorbent were Ca, O, Fe and Na and lime, as high as about 94.25% was the main structural component of the total weight. Produced nanoadsorbent was not soluble in water. It was also shown that by increasing the nanoadsorbent dose from 0.5 to 5 g/100 ml, the removal of humic acid increased from 62.3% to 97.4%. An inverse relationship was found between initial concentration and adsorption capacity, so that a decreasing rate of 33% for humic acid removal was observed by increasing pH from 5 to 10. Temperature increase from 25°C to 40°C, resulted in an increase in humic acid removal from 76.8% to 91.4% and its adsorption on the adsorbent could be better described by Freundlich isotherm (n = 0.016, K_f = 0.013 and R² = 0.74). The most fitted adsorption kinetic model was pseudo-second order model.

Conclusions

The chemical structure of nanoadsorbent was proper and free from harmful substances. Despite the relative good condition of the effective surface, due to the large size of the shell, the overall micropore volume was low. Hence the qualitative characteristics the adsorbent caused the absorption capacity of humic acid to be low (0.96 mg/g).