Selective and effective adsorption of methyl blue by barium phosphate nano-flake

Analyzing synthesis routes for BaCuPO4: implications for hydrogen evolution and supercapattery performance

In recent years, energy storage and conversion tools have evolved significantly in response to rising energy demands. Owing to their large surface area, superior electric and chemical stabilities, and thermal conductivities, barium copper phosphate (BaCuPO4) materials are promising electrode materials for electrochemical energy storage systems. In this study, the synthesis of nanostructures (NSs) using hydrothermal and chemical precipitation methods and exploring the electrochemical characteristics of BaCuPO4 in asymmetric supercapacitors provides a comparative investigation. Systematic characterization shows that nanomaterials prepared by applying the hydrothermal method have a more crystalline and large surface area than chemical precipitation. In the three cell arrangements, the hydrothermally prepared BaCuPO4 NSs delivered a high specific capacity (764.4 C g-1) compared to the chemical precipitation route (660 C g-1). Additionally, the supercapattery associated with the two electrode assemblages delivers an optimum specific capacity of 77 C g-1. The energy and power density of BaCuPO4//AC NSs were 52.13 W h kg-1 and 950 W kg-1, respectively. A durability test was also performed with BaCuPO4//AC NSs for 5000 consecutive cycles. Further, the coulombic efficiency and capacity retention of BaCuPO4//AC after 5000 cycles were 81% and 92%, respectively. Bimetallic phosphate is comparatively suggested for future perspectives towards HER to overcome the performance of single metal phosphate materials. This is the first approach, we are aware of, for investigating the electrochemical behavior of BaCuPO4, and our results suggest that it may be useful as an electrode material in electrochemical systems requiring high energy and rate capabilities.

Environmental-Friendly Adsorbent Composite Based on Hydroxyapatite/Hydroxypropyl Methyl-Cellulose for Removal of Cationic Dyes from an Aqueous Solution

The aim of this study is to develop a new, efficient, and inexpensive natural-based adsorbent with high efficacy for the cationic dye methylene blue (MB). A natural-based nanocomposite based on hydroxyapatite (HAp) and hydroxypropyl methylcellulose (HPMC) was selected for this purpose. It was synthesized by the dissolution/reprecipitation method. A film with a homogeneous and smooth surface composed of nanoparticles was prepared from the nanocomposite. HPMC and HAp biopolymers were selected due to their compatibility, biodegradability, and non-toxicity. Total reflectance infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and calorimetric/thermal gravimetric (DSC/TGA) analysis results revealed the existence of strong physical interaction between the composite components. Scanning electron microscopy (SEM) observations show a composite sheet with a homogenous and smooth surface, indicating excellent compatibility between HPMC and HAp in the composite. The nanocomposite was evaluated as an adsorbent for organic dyes in an aqueous solution. The effects of solution pH, initial MB concentration, composite concentration, and adsorption time on the adsorption efficiency were evaluated. The highest adsorption rate was seen as 52.0 mg of MB/g composite. The adsorption rate reached equilibrium in about 20 min. Fitting of the adsorption data to the Langmuir and Freundlich adsorption models was investigated. Results showed that the adsorption process follows the Langmuir isotherm model. The kinetic study results revealed that the adsorption process was pseudo-second-order. The herein composite is an excellent alternative for use as contemporary industrial-scale adsorbents.

Emerging novel polymeric adsorbents for removing dyes from wastewater: A comprehensive review and comparison with other adsorbents

Dye molecules are one of the most hazardous compounds for human and animal health and the excess intake of these materials can create toxic impacts. Several studies show the practicality of the adsorption process for dye uptake from wastewaters. In recent years, various adsorbents were used to be efficient in this process. Among all, polymeric adsorbents demonstrate great applicability in different environmental conditions and attract many researchers to work on them, although there is not enough reliable and precise information regarding these adsorbents. This study aims to investigate some influential parameters such as their type, physical properties, experimental conditions, their capacity, and further modeling along with a comparison with non-polymeric adsorbents. The influence of the main factors of adsorption capacity was studied and the dominant mechanism is explained extensively.

Azo-dye derived oxidized-nitrogen rich carbon sheets with high adsorption capability for dye effluent under both batch and continuous conditions

The removal of methyl blue (MB) from wastewater using graphene and its derivative is very successful due to their high aromaticity which drives adsorption via π-π and electron-donor-acceptor (EDA) interactions; however, graphene is expensive and difficult to synthesize, which limit its practical application. Meanwhile, low aromatic carbon materials (LACM) derived from farm-water and other materials are cheaper and easier to synthesize but have limited π-π and EDA interactions and low adsorption capacity. Herein, we demonstrate that LACM with oxidized-nitrogen (N-O^-) functionality overcomes this limitation via chemisorption of MB through a combination of hydrophobic-hydrophobic interactions and EDA interactions. This is confirmed using XPS analysis of LACM/N-O^- post MB adsorption. Consequently, a remarkable adsorption capacity of 3904 mg g^-1 is achieved under batch condition which is the highest ever reported for any MB adsorbent. Furthermore, LACM/N-O^- works equally well under continuous-flow adsorption conditions which shows its practicability. Amongst several LACM precursors tested, only Azo-dyes are able to generate LACM/N-O^- implying that the NN moiety is key to N-O^- formation. A carbonization temperature of 700 °C generates the highest N-O^- sites hence the highest adsorption capacity. Characterization of LACM/N-O^- is done mainly using BET, XPS, Raman, TGA, and FTIR analysis.

Enhanced simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi) ions from aqueous solution using cassava root husk-derived biochar loaded with ZnO nanoparticles

This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi). By conducting batch-mode experiments, it was concluded that 3% w/w was the best impregnation ratio for the modification of CRHB using ZnO-NPs, and was denoted as CRHB-ZnO3 in this study. The optimal conditions for heavy metal adsorption were obtained at a pH of 6–7, contact time of 60 min, and initial metal concentration of 80 mg L⁻¹. The heavy metal adsorption capacities onto CRHB-ZnO3 showed the following tendency: Pb(ii) > Cd(ii) > As(iii) > Cr(vi). The total optimal adsorption capacity achieved in the adsorption of the 4 abovementioned metals reached 115.11 and 154.21 mg g⁻¹ for CRHB and CRHB-ZnO3, respectively. For each Pb(ii), Cd(ii), As(iii), and Cr(vi) metal, the maximum adsorption capacities of CRHB-ZnO3 were 44.27, 42.05, 39.52, and 28.37 mg g⁻¹, respectively, and those of CRHB were 34.47, 32.33, 26.42 and 21.89 mg g⁻¹, respectively. In terms of kinetics, both the pseudo-first-order and the pseudo-second-order fit well with metal adsorption onto biochars with a high correlation coefficient of R², while the best isothermal description followed the Langmuir model. As a result, the adsorption process of heavy metals onto biochars was chemisorption on homogeneous monolayers, which was mainly controlled by cation exchange and surface precipitation mechanisms due to enriched oxygen-containing surface groups with ZnO-NP modification of biochar. The FTIR and EDS analysis data confirmed the important role of oxygen-containing surface groups, which significantly contributed to removal of heavy metals with extremely high adsorption capacities, comparable with other studies. In conclusion, due to very high adsorption capacities for metal cations, the cassava root husk-derived biochar modified with ZnO-NPs can be applied as the alternative, inexpensive, non-toxic and highly effective adsorbent in the removal of various toxic cations.

This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi).

Successive removal of Pb2+ and Congo red by magnetic phosphate nanocomposites from aqueous solution

The successive removal of Pb²⁺ and Congo red (CR) from aqueous solution by three magnetic phosphate nanocomposites (Fe₃O₄@Sr₅(PO₄)₃(OH), Fe₃O₄@Ba₃(PO₄)₂, and Fe₃O₄@Sr_5xBa_3x(PO₄)₃(OH), denominated FSP, FBP, and FSBP, respectively) was systematically investigated in comparison with Fe₃O₄ (denominated F) nanoparticle. FSP, FSBP, F, and FBP exhibited a high removal capacity of 351, 272, 76, and 23 mg/g for Pb²⁺, respectively. These materials could be reclaimed by magnetic separation and then used for successive CR remediation, showing a high CR removal capacity of 224, 163, 126, and 61 mg/g, respectively. The isothermal and kinetic behavior fitted well with the Langmuir model and pseudo-second-order model, respectively. The successive removal mechanism by these magnetic phosphates was proposed to be the ion exchange between Pb²⁺ and Sr²⁺ in the lattice and then the loaded Pb²⁺ could contact with anionic dye CR to form precipitation on the surface of materials, inhibiting the leaching of Pb²⁺ ions from the reclaimed materials back into water. In addition, these materials showed good reusability and practical application. This study demonstrated the potential of these low cost phosphate nanocomposites as promising materials for successive removal of Pb²⁺ and CR from water.

Effective adsorption of malachite green using magnetic barium phosphate composite from aqueous solution

Magnetic Ba₃(PO₄)₂/Fe₃O₄-nanoparticle (called BPFN) was prepared, characterized, and developed as a low-cost adsorbent for malachite green (MG) from aqueous solution. Factors such as adsorption temperature, pH of solution, dosage of adsorbent, adsorption kinetics and isotherms were investigated. The maximum adsorption capacity obtained in this work was 1639mgg^-1 at 45°C and pH6. The adsorption process fitted the pseudo-first-order kinetic model and Langmuir isotherm model. Evidences from zeta potential, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) data revealed that the adsorption process was driven by electrostatic attraction, the interaction between Lewis base N(CH₃)₂ in MG and Lewis acid Ba sites of BPFN. In addition, the BPFN could be easily regenerated by a magnet and the adsorption capacity maintained at 70% after five cycles. The present study suggests that the BPFN had high potential of removing MG from wastewater.

Facile synthesis of 3D hierarchical MnO2 microspheres and their ultrahigh removal capacity for organic pollutants

The weight ratio of degraded MB to catalyst (40 mg mg⁻¹) is much higher than most reported values.

Removal of Cu (II) and Pb (II) from Aqueous Solution using engineered Iron Oxide Nanoparticles

Nano-sized Fe₃O₄ and Fe₂O₃ were synthesized using a precipitation method. The nanomaterials were tested as adsorbents for the removal of both Cu²⁺ and Pb²⁺ ions. The nanomaterials were characterized using X-ray powder diffraction to determine both the phase and the average grain size of the synthesized nanomaterials. Batch pH studies were performed to determine the optimum binding pH for both the Cu²⁺ and Pb²⁺ to the synthesized nanomaterials. The optimum binding was observed to occur at pH 4 and above. Time dependency studies for Cu²⁺ and Pb²⁺ showed the binding occurred within the first five minutes of contact and remained constant up to 2 hours of contact. Isotherm studies were utilized to determine the binding capacity of each of the nanomaterials for Cu²⁺ and Pb²⁺. The binding capacity of Fe₃O₄ with Cu²⁺ and Pb²⁺ were 37.04 mg/g and 166.67 mg/g, respectively. The binding capacities of the Fe₂O₃ nanomaterials with Cu²⁺ and Pb²⁺ were determined to be 19.61 mg/g and 47.62 mg/g, respectively. In addition, interference studies showed no significant reduction in the binding of either Cu²⁺ or Pb²⁺ to the Fe₃O₄ or Fe₂O₃ nanomaterials in the presence of solutions containing the individual ions Na⁺, K⁺, Mg²⁺ and Ca²⁺ or a solution consisting of a combination of all the aforementioned cations in one solution.

Three-Dimensional Assembly of Yttrium Oxide Nanosheets into Luminescent Aerogel Monoliths with Outstanding Adsorption Properties

The preparation of macroscopic materials from two-dimensional nanostructures represents a great challenge. Restacking and random aggregation to dense structures during processing prevents the preservation of the two-dimensional morphology of the nanobuilding blocks in the final body. Here we present a facile solution route to ultrathin, crystalline Y2O3 nanosheets, which can be assembled into a 3D network by a simple centrifugation-induced gelation method. The wet gels are converted into aerogel monoliths of macroscopic dimensions via supercritical drying. The as-prepared, fully crystalline Y2O3 aerogels show high surface areas of up to 445 m(2)/g and a very low density of 0.15 g/cm(3), which is only 3% of the bulk density of Y2O3. By doping and co-doping the Y2O3 nanosheets with Eu(3+) and Tb(3+), we successfully fabricated luminescent aerogel monoliths with tunable color emissions from red to green under UV excitation. Moreover, the as-prepared gels and aerogels exhibit excellent adsorption capacities for organic dyes in water without losing their structural integrity. For methyl blue we measured an unmatched adsorption capacity of 8080 mg/g. Finally, the deposition of gold nanoparticles on the nanosheets gave access to Y2O3-Au nanocomposite aerogels, proving that this approach may be used for the synthesis of catalytically active materials. The broad range of properties including low density, high porosity, and large surface area in combination with tunable photoluminescence makes these Y2O3 aerogels a truly multifunctional material with potential applications in optoelectronics, wastewater treatment, and catalysis.

High capacitive amorphous barium nickel phosphate nanofibers for electrochemical energy storage

Ba_xNi_3−x(PO₄)₂(0 <x< 3) amorphous nanofibers with excellent supercapacitive performance were synthesized through a facile cation-exchange method.

Fast adsorption of methyl blue on zeolitic imidazolate framework-8 and its adsorption mechanism

Zeolitic imidazolate framework-8 (ZIF-8) is synthesized and the adsorption behavior and mechanism of methyl blue (MB) are studied in detail.

Hierarchically porous silicon-carbon-nitrogen hybrid materials towards highly efficient and selective adsorption of organic dyes

The hierarchically macro/micro-porous silicon–carbon–nitrogen (Si–C–N) hybrid material was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp2-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir model, the adsorption capacity is 1327.7 mg·g⁻¹ and 1084.5 mg·g⁻¹ for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically porous Si–C–N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.

Adsorption of anionic MO or cationic MB from MO/MB mixture using polyacrylonitrile fiber hydrothermally treated with hyperbranched polyethylenimine

One-step hydrothermal treatment of polyacrylonitrile fiber (PANF) with hyperbranched polyethylenimine (HPEI) resulted in zwitterionic PANF-g-HPEI that contained not only the grafted HPEI moieties but also many COOH groups generated in situ. Increasing the weight gain of PANF-g-HPEI from 10% to 90% resulted in the increase of its COOH, amino and amide groups from 0.12 to 1.86 mmol/g, 1.44 to 8.90 mmol/g, and 0.67 to 2.12 mmol/g, respectively. Dye adsorption experiments demonstrated that (1) such PANF-g-HPEIs could effectively adsorb anionic Methyl Orange (MO) or cationic Methylene Blue (MB), through the pretreatment with acidic or basic solution, respectively; (2) PANF-g-HPEIs could selectively adsorb the anionic MO or the cationic MB from MO/MB mixture through the pretreatment with solution of pH=5 or 10, respectively; (3) the cationic or anionic dyes adsorbed by PANF-g-HPEIs could be reversibly desorbed by the aqueous solution of pH=1 or 10, respectively; (4) PANF-g-HPEI could be recycled efficiently, and its dye adsorption performances did not show pronounced loss even after 10 adsorption/desorption cycles, superior to PANF treated with the low molar-mass polyamines.

Barium recovery by crystallization in a fluidized-bed reactor: effects of pH, Ba/P molar ratio and seed

The effects of process conditions, including upward velocity inside the column, the amount of added seed and seed size, the pH value of the precipitant or the phosphate stream and the Ba/P molar ratio in a fluidized-bed reactor (FBR) were studied with a view to producing BaHPO₄ crystals of significant size and maximize the removal of barium. XRD were used to identify the products that were collected from the FBR. Experimental results show that an upward velocity of 48 cmmin(-1) produced the largest BaHPO₄ crystals with a size of around 0.84-1.0mm. The addition of seed crystals has no effect on barium removal. The use of a seed of a size in the ranges unseeded<0.149-0.29 mm<0.149 mm<0.29-0.42 mm produced increasing amounts of increasingly large crystals. The largest BaHPO₄ crystals were obtained at pH 8.4-8.8 with a Ba/P molar ratio of 1.0. In the homogeneous and heterogeneous processes, around 98% of barium was removed at pH 8.4-8.6 and [Ba]/[P]=1.0. The XRD results show that a significant amount of barium phosphate (Ba₃(PO₄)₂) was obtained at pH 11. The compounds BaHPO₄ and BaO were present at a pH of below 10.

Heterogeneous Fenton-like discoloration of Rhodamine B using natural schorl as catalyst: optimization by response surface methodology

A cationic dye, Rhodamine B (RhB), could be efficiently discolored by heterogeneous Fenton-like reaction catalyzed by natural schorl. In this work, with the main goal of the optimization for RhB discoloration, central composite design under the response surface methodology (RSM) was employed for the experiment design and process optimization. The significance of a second-order polynomial model for predicting the optimal values of RhB discoloration was evaluated by the analysis of variance and 3D response surface and counter plots for the interactions between two variables were constructed. The Pareto graphic analysis of the discoloration process indicated that, among all the variables, solution pH (X 3, 47.95 %) and H2O2 concentration (X 1, 24.39 %) had the largest influences on the heterogeneous Fenton-like discoloration of RhB. Based on the model prediction, the optimum conditions for RhB discoloration were determined to be 45 mM H2O2 concentration, 2.5 g/L schorl dosage, solution pH 2, and 110 min reaction time, with the maximum RhB discoloration ratio of 98.86 %. The corresponding experimental value of RhB discoloration ratio under the optimum conditions was determined as 99.31 %, which is very close to the optimized one, implying that RSM is a powerful and satisfactory strategy for the process optimization.