pHzpc Values Research Articles

Enhanced Treatment of Antimony Mine Wastewater by Sulfidated Micro Zerovalent Iron (S-mZVI).

Commercial micron zerovalent iron (mZVI) and sulfur were used to prepare sulfidated micro zerovalent iron (S-mZVI) through ball milling. The corrosion potentials of mZVI and S-mZVI were -0.01 and -0.37 V, respectively, indicating S-mZVI possessed a stronger electron-donating ability. The practical antimony mine wastewater (C0(Sb(V)) = 3.8296 mg/L, pH = 8.29) was treated. If meeting the national discharge standard of 5 μg/L, 2.0 g/L mZVI and 1.6 g/L S-mZVI were required within 120 min. Passing N2 or reducing wastewater pH enhanced the treatment of Sb(V) by S-mZVI, in which the wastewater acidification was more effective. Once the wastewater pH was adjusted to 3.00, only 0.7 g/L S-mZVI and 40 min long time were needed to achieve the emission below 5 μg/L. Even S-mZVI underwent four cycles, and the final concentration of Sb(V) was as low as 4.67 μg/L. As the pHzpc value was 4.09 and the corrosion potential was -0.56 V at pH 3.0, the electron-donating ability of S-mZVI as well as the electrostatic attraction between the surface of S-mZVI and Sb(V) increased. Sulfidation of mZVI and then application under the acid condition significantly improved the treatment efficiency of Sb(V).

Designing and evaluation of thiosemicarbazide-functionalized/ion-imprinted cellulose for selective removal of mercury (II) ion

For aquatic ecosystems, Hg2+ removal from wastewater is crucial. However, getting high-efficiency Hg2+ extraction is still a challenge due to slow rates and poor selectivity. The active thiosemicarbazide (TSC) chelating units were added to the cellulose (CE) in this work using a novel synthetic pathway. The TSC-CE derivative was then used to produce a Hg2+ ion-imprinted sorbent. Initially, the Michael reaction was used to yield cyanoethyl cellulose (CEC). TSC units were combined by a chemical reaction with the added -CN groups. After Hg2+ was attached to TSC-CE, it was cross-linked with glutaraldehyde before being eliminated via elution with HNO3/EDTA. The Hg2+ imprinted sorbent (Hg-TSC-CE) achieved improved adsorption selectivity for Hg2+ and significantly higher adsorption capacity (qm = 353 ± 0.5 mg/g) in comparison to the non-imprinted sorbent. The FTIR and XPS studies both gave strong evidence supporting the kinetic results for the pseudo-second-order model, which said that coordination is the main process of adsorption. The Langmuir model also well explained the isotherms. It showed that Hg2+ mainly adsorption took place in monolayers, with a pHZPC value of about 5.6. Moreover, the Hg2+ adsorption was endothermic, and the optimum pH was observed at 5.

Box-Behnken design optimization of bimetallic-organic frameworks for effective removal of tartrazine food dye from aqueous solutions

Lanthanum and tin-based hetero bimetallic organic frameworks (MOFs) in the form of stacked nanorods (La/Sn@MOF) exhibit promising capabilities in removing the yellow dye Tartrazine (E102) from aqueous solutions. Various techniques such as SEM, XRD, XPS, FTIR, and BET were employed to assess the adsorbent, revealing a significant surface area of 736.82 m2/g. The study thoroughly investigated the impact of pH, initial dye concentration, adsorbent dose, contact time, and temperature on the elimination of E102 dye. The clearance of tartrazine follows the Langmuir isotherm and pseudo-second-order kinetics, with a maximum adsorption capacity of 694.72 mg/g according to the Langmuir isotherm model. The pHzpc value of 6.41 suggests favorable adsorption of anionic dyes like E102 dye at pH levels below 6.4. The adsorption process was characterized by adsorption energy of 29.46 kJ/mol, indicating a chemisorption process. Thermodynamic analysis revealed that the adsorption processes were both endothermic and spontaneous, as evidenced by the negative values for ΔGo and positive values for ΔHo. La/Sn@MOF proved to be a straightforward and effective method for treating industrial wastewater, with the added benefit of being reusable for up to five cycles. Interaction between La/Sn@MOF and E102 dye was found to involve hydrogen bonding, pore filling, and π-π interactions, among other mechanisms. Optimization of the adsorption procedure was achieved using the Box-Behnken Design method (BBD).

Enhanced removal of aqueous arsenic(III) by sulfidated nanoscale zero-valent iron under oxic conditions: Performance and mechanism

Although sulfidated nanoscale zero-valent iron (S-nZVI) has shown significant promise in the removal of aqueous inorganic arsenic (As), there is a scarcity of studies comprehensively investigating their performance under oxic conditions, as well as the mechanism involving oxidation being elucidated. In this study, the synthesized S-nZVI exhibited a distinctive core-shell structure, characterized by an outer shell comprising iron oxides and FeS, while also demonstrating increased specific surface areas and decreased pHZPC value. Batch experiments revealed that sulfidation significantly enhanced the As(III) removal efficiency of nZVI under oxic conditions by increasing both the reaction rates and adsorption capacity (qm = 495.23 mg/g). Furthermore, several critical factors influencing the As(III) removal by S-nZVI were investigated, indicating that increased initial As(III) concentrations, initial pH values, and co-existing anions concentrations had negative impacts on the removal process; however, an increase in ionic strength showed certain positive effects. Based on the profiles of As and Fe, roles of reactive species, and characterization of reacted products, it could be concluded that As(III) removal by S-nZVI involves the synergistic effect of adsorption, co-precipitation, and oxidation. More importantly, sulfidation facilitated the corrosion of Fe0, accelerating the release of Fe2+ and promoting the activation of single-electron molecular oxygen reactions, thereby further enhancing the total As removal efficiency. This study highlights the excellent potential of S-nZVI for effectively removing As(III) under oxic conditions.

Synthesis of Graphene Nanoplatelet-Alginate Composite Beads and Removal of Methylene Blue from Aqueous Solutions

The discharge of various types of wastewater into natural streams leads to significant problems by increasing the toxicity of the wastewater. For this reason, methods and materials are being developed by researchers in line with effective, economic, and environmental principles. In this study, the removal of methylene blue, a toxic dyestuff, from aqueous solutions was investigated by synthesizing sodium alginate (SA) and graphene nanoplatelet-sodium alginate composite (SA-GNP) beads. The structural characteristics of the materials were analyzed using FTIR, TGA, optical microscope, and SEM methods. All parameters determining the efficiency of the methylene blue adsorption system were optimized in a batch system. The effects of various factors, such as adsorbent amount, contact time, adsorption temperature, dye concentration, solution pH, pHzpc values of SA and SA-GNP beads, presence of different ions, and beads swelling, on the adsorption process, were investigated. To investigate the mechanism of the adsorption system, the adsorption data were fitted to a non-linear form of the Langmuir, Freundlich, and Temkin equilibrium isotherm models, as well as the Pseudo-first-order (PFO), Pseudo-second-order (PSO), and Bangham kinetic models. High regression coefficients were achieved in the studied kinetic and isotherm models (0.86 ≤ R2 ≤ 0.99), and the experimental data were found to be compatible with the model parameters. Maximum adsorption capacities (qm) of 167.52 mg/g and 290.36 mg/g were obtained for the SA and SA-GNP adsorbents, respectively, at 308 K. The optimum temperature for both adsorption systems was found to be 308 K. The efficiency of methylene blue dyestuff removal was improved with graphene nanoplatelet-based adsorbents.

High capacity aluminium substituted hydroxyapatite incorporated granular wood charcoal (Al-HApC) for fluoride removal from aqueous medium: Batch and column study

In this study, aluminium substituted hydroxyapatite (Al-HAp) was synthesized in-situ on granular commercial wood charcoal at room temperature for fluoride removal from groundwater. Granular size (0.5–3.0 mm) of the carbon particles was selected considering the practical application of the final adsorbent in a packed-bed column filter. The adsorbent was characterized thoroughly. The Al-HAp phase was precipitated inside the pore channel as well as on the surface of highly porous wood charcoal matrix. The adsorbent had surface area of 442 m2/g and pHzpc value was 5. The maximum fluoride adsorption capacity at 303 K was achieved as 105 mg/g which is the highest for any granular adsorbent reported till date for adsorption of fluoride. Batch studies were used to deduce the effective role of pH, temperature and ion selectivity on adsorption efficiency. The reusability of the media was tested upto five cycles after consecutive regeneration with 1 M NaOH. Using the developed media, continuous column run experiments were conducted at different operating conditions, viz., bed volume, flow rate and feed concentration. The maximum number of bed volume was obtained as 1415 for a 30 cm bed height with flow rate 10 L/day and feed concentration of 3 mg/L. A fundamental mass transport model based on pore-diffusion was used to simulate breakthrough behavior in fixed-bed column runs with the synthetic and real contaminated groundwater. The relevant model parameters, namely, fixed bed mass transfer coefficient (kfb), effective pore diffusivity (Dp) and the coefficient of axial dispersion (Ez) were estimated.

Selective removal of uranyl ions using ion-imprinted amino-phenolic functionalized chitosan

The recovery of uranium from aqueous effluents is very important for both the environment and the future of nuclear power. However, issues of sluggish rates and poor selectivity persist in achieving high-efficiency uranium extraction. In this study, uranyl (UO22+) ions were imprinted on an amino-phenolic chitosan derivative using an ion-imprinting method. First, 3-hydroxy-4-nitrobenzoic acid (HNB) units were joined to chitosan via amide bonding, followed by reducing the -NO2 residues into -NH2. The amino-phenolic chitosan polymer ligand (APCS) was coordinated with UO22+ ions, then cross-linked with epichlorohydrin (ECH), and finally the UO22+ ions were taken away. When compared to non-imprinted sorbent, the resulting UO22+ imprinted sorbent material (U-APCS) recognized the target ions preferentially, allowing for much higher adsorption capacities (qm = 309 ± 1 mg/g) and improved adsorption selectivity for UO22+. The FTIR and XPS analyses supported the pseudo-second-order model's suggestion that chemisorption or coordination is the primary adsorption mechanism by fitting the data well in terms of kinetics. Also, the Langmuir model adequately explained the isotherms, suggesting UO22+ adsorption in the form of monolayers. The pHZPC value was estimated at around 5.7; thus, the optimum uptake pH was achieved between pHs 5 and 6. The thermodynamic properties support the endothermic and spontaneous nature of UO22+ adsorption.

Removal of natural organic matter fractions by adsorptive asymmetric ceramic membrane functionalized with in situ phytogenic nanoscale zero valent iron: Performance and Fenton cleaning strategy

AbstractExtant literature has demonstrated that conventional water treatment processes especially in developing countries struggle in completely removing detrimental organic loads. Emerging research delineates nanomaterials such as nanoscale zero valent iron (nZVI) to have excellent performance in organic matter removal from aqueous media. In this work, nZVI particles were prepared from the liquor of commercially available green tea and supported on kaolin (K‐nZVI) and investigated as an adsorbent for natural organic matter (NOM) sequestration from aquatic media. Further, the asymmetric ceramic membrane was prepared by incorporating the developed adsorbent on a concrete support for the removal of NOM. A Fenton cleaning strategy was developed to mitigate fouling. The Brunauer–Emmett–Teller (BET) results revealed the developed adsorbent surface area was greater compared to raw kaolin (27.07 and 11.64 m3 g−1, respectively). The scanning electron microscopy (SEM) imagery of the developed adsorbent showed the particle staking was presented as paper slices of varying sizes, an indication of dispersed particles with characteristic plate‐like fragments. The synthesized membrane exhibited a pHZPC value of 4.79 ± 0.03. This meant at pH above 4.79 ± 0.03, the membrane would be negatively charged, and conversely at pH below the pHZPC value. Membrane fouling due to bovine serum albumin (BSA) deposition showed a 50% flux decline in the first 60 min, coinciding with the rapid adsorption capacity within the same time frame. The optimal cleaning parameters of pH (4.5) and H2O2 (5 mM) gave the best flux recovery rates. This work demonstrated an efficient Fenton cleaning strategy to regenerate the developed membrane.

GREEN SYNTHESIS OF IRON-OXIDE NANOPARTICLES USING SCRAP IRON AS PRECURSOR FOR THE REMOVAL OF PB (II) FROM AQUEOUS MEDIUM

In the present study, low-cost, environmentally friendly, single-step, high productive novel Iron-oxide nanoparticles (NPs) were prepared from scrap iron using a green synthesis method to remove Pb (II) from aqueous solution. The characterization of synthesized nanoparticles was conducted by UV-vis spectroscopy. The crystalline structure and the phase change were clarified by XRD. FE-SEM was done to know the morphology of iron oxide nanoparticles, and the average surface area of 46.856 m2/g was found by the BET surface area analyzer. The XRD plot shows that the obtained magnetite Fe3O4 combines FeO and Fe2O3 as the synthesis was conducted in the open atmosphere. The SEM images confirm the formation of iron oxide nanoparticles with a size of 31 nm. The removal efficiency of the adsorbent was carried out by optimizing the different operational parameters like pH, time, adsorbent dosage, initial concentration of metal ion, contact time by batch studies. The obtained pHzpc (pH 5.7) value indicates that the adsorption process will be favorable at higher pH. The maximum removal efficiency and uptake capacity of lead were 98% and 68.07 mg/g, respectively. Adsorption data obtained were analyzed with Langmuir and Freundlich isotherm equations. The equilibrium data are fitted by Langmuir isotherm in a superior way than that of Freundlich isotherm. The results show that homogeneous adsorption of the metal ion favors heterogeneous adsorption. The maximum adsorption capacity of iron oxide NPs was calculated through Langmuir isotherm was Qmax (68.07) mg/g. Moreover, the adsorption of metal ions with time was also analyzed with the pseudo 1st and pseudo 2nd kinetic equations. The kinetic data are fitted more in the pseudo 2nd order reaction. Adsorption capacity calculated through pseudo 2nd order equation was qe (51.81) mg/g. This literature verifies that NPs synthesized from scrap iron as precursors prove to be an attractive option for removing heavy metals.

"ADSORPTION OF AMARANTH ONTO NATURAL PEANUT HUSK AND CATIONIC SURFACTANT-MODIFIED PEANUT HUSK FROM AQUEOUS SOLUTION: KINETIC, ISOTHERM AND THERMODYNAMIC ANALYSES "

Natural peanut husk (NPH) and hexadecyltrimethylammonium bromide (CTAB)-modified peanut husk (MPH) were used to study the adsorption characteristics of amaranth in aqueous solution. NPH and MPH were characterized by Fourier transform infrared (FTIR) spectroscopy. The pHzpc values of NPH and MPH were estimated to be 5.06 and 5.96, respectively. The adsorption of amaranth onto both adsorbents was confirmed by the observations of field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) analysis. Adsorption kinetic experiments were conducted at various contact time, solution pH, initial dye concentration, temperature, and ionic strength, respectively. Dye adsorption kinetics pursued the pseudo-second-order kinetic model. Adsorption isotherms obeyed the Langmuir model with the highest dye adsorption capacity of 20.88 µmol/g for NPH at pH 2, and 117.65 µmol/g for MPH at pH 4. The values of activation energy (Ea) for the adsorption process were determined to be 48.68 kJ/mol for NPH and 16.92 kJ/mol for MPH, respectively. Thermodynamic data confirmed that amaranth adsorption onto both adsorbents was an endothermic spontaneous physisorption process. The release of amaranth from dye-loaded adsorbents was performed in HCl solution (pH 1) and the recycled adsorbents were utilized six times without significant loss of their adsorption capacity.

Role of pH on photocatalytic degradation of phenol derivatives using metal supported on mesoporous materials

Photocatalysis is a promising advanced oxidation process (AOPs). It is often used in the degradation of phenolic derivatives due to their simplicity and easy handling, by converting organic molecules with total mineralisation into nontoxic H2O and CO2. In this study, a combination of microwave-assisted (MW) and facile electrochemical method was applied in the synthesis of catalysts (Fe-MTN and Cu-MZN). The characterisation of catalysts was tested using XRD, UV–Vis DRS and FTIR. It was found that there was no new bonding formed when Fe was introduced onto MTN, while the introduction of Cu onto MZN formed a new Zn-O-Cu. The introduction of Fe and Cu onto MTN and MZN also decreased the bandgap energy from 3.15 to 2.35 eV and 2.92 to 2.63 eV, respectively. The pH of the solution is one of the essential parameters that need to be measured in the photocatalytic process due to the amphoteric properties of semiconductor, which influenced the surface-charged properties of the catalysts. Fe-MTN and Cu-MZN were used in photocatalytic degradation of 2-chlorophenol (2-CP) and 2,4-diclorophenol (2,4-DCP), respectively. After the effect of pH over 2-CP and 2,4-DCP was tested in the range of 3 to 11, the greatest degradation of 2-CP using Fe-MTN was at pH 5 with 99% while 100% degradation of 2,4-DCP at pH 3 for Cu-MZN. These results are probably due to the amphoteric characteristic of catalyst, where it can be tested using point zero charged (pHZPC). The pHZPC value of Fe-MTN and Cu-MZN was 6.1 and 5.5, respectively illustrated that the photoactivity of both catalysts better in acidic condition compared to an alkaline condition.

Radiation synthesis and characterization of heterogeneous magnetic nanocomposites of 2-hydroxyethyl methacrylate for catalytic degradation of sandocryl blue dye

Recently, nanostructured polymeric materials with unique morphological and structural properties became promising for removal of the dyes and contaminants from wastewater and industrial effluent. Herein, radiation preparation of 2-hydroxyethyl methacrylate (HEMA) hydrogel and heterogeneous poly(HEMA) magnetic nanocomposites incorporated with various contents of Fe3O4 or Fe3O4/PbO hybrid nanoparticles (NPs), namely poly(HEMA)-Fe3O4 and poly(HEMA)-Fe3O4/PbO nanocomposites were investigated to promote the decolorization of sandocryl blue dye. Fe3O4 or Fe3O4/PbO hybrid NPs were synthesized by alkaline co-precipitation method. Characterization of nanocomposites was confirmed by FTIR, TEM, XRD, SEM, EDS and VSM. XRD results of pure Fe3O4/PbO NPs and poly (HEMA)-Fe3O4/PbO nanocomposites showed successful coupling between Fe3O4 and PbO NPs within the poly(HEMA) networks. TEM results confirmed that the Fe3O4/PbO NPs have spherical shape and highly dispersed with average diameter of 16.7–23.4 nm, Both poly(HEMA)-Fe3O4 and poly(HEMA)-Fe3O4/PbO exhibit ferromagnetic behavior as confirmed through VSM measurements. By comparing the possible applicability of prepared poly(HEMA)-Fe3O4 and poly(HEMA)-Fe3O4/PbO nanocomposites for the decolorization of sandocryl blue dye, it is concluded that the poly(HEMA)-Fe3O4/PbO nanocomposite of 25% hybrid NPS ratio was the highest decolorization effect even after 5th cycles of regeneration. The effect of contact time, temperature, adsorbent dosage, and pH on dye decolorization onto poly(HEMA)-Fe3O4/PbO were intensively evaluated. The maximum decolorization poly(HEMA)-Fe3O4/PbO nanocomposite for dye was 99.8% after 90 min at pH 9 using 250 mg/L dye concentration. The pHzpc value of poly (HEMA)-Fe3O4/PbO was found to be 6.6 as estimated by mass titration method. Based on he kinetic, isothermal, and thermodynamic studies the discoloration process is endothermic and spontaneous in nature, best fitted by the pseudo-second order kinetic and Langmuir isotherm model. The synthesized hybrid nanostructured catalyst poly(HEMA)-Fe3O4/PbO could be used as powerful catalyst for degradation of dye pollutants from wastewater with high decolorization efficiency as well as the degradation of mixture of dyes composed of methyl orange, acid red 18 and sandocryl blue dye of high concentration.

Equilibrium, kinetic and thermodynamic study of diazinon adsorption from water by clay/GO/Fe3O4: Modeling and optimization based on response surface methodology and artificial neural network

In this study, a new magnetic composite consisted of clay/graphene oxide/Fe3O4 was used for elimination of Diazinon (pesticide) from aqueous solutions. Analysis of the structural properties and surface morphology of the composite showed that the composite was well-synthesized and had a crystalline and multilayere structure. Magnetic saturation value was determined to be 39.9 emu/g. Its pHZPC value and active surface area was 7.1 and 185.7m2/g, respectively.In order to investigate the effects of pH, temperature, contact time, initial concentration of Diazinon and composite dosage on adsorption efficiency and modeling adsorption process, the response surface methodology-central composite design (RSM-CCD) and artificial neural network methods (ANN) were used. The results obtained through analysis using response surface methodology showed that the maximum amount of adsorption was 98.79% at 25.91 °C, while pH, initial concentration, contact time, and adsorbent dose were 6.9, 1.2 ppm, 24.6 min, and 1.1 g/L, respectively. Comparison between results obtained from CCD modeling and artificial neural network proved that both methods had high ability to predict the adsorption process but the CCD method had higher coefficient of determination and lower error. The equilibrium and kinetic study of the process showed that the Langmuir-Freundlich isotherm model, pseudo-second-order, and Elovich kinetics are all suitable for expressing the adsorption process. In addition, the adsorption mechanism obeyed double-exponential model that combines external and internal diffusions.Results of thermodynamic study suggested that the Diazinon adsorption on clay/GO/Fe3O4 was a spontaneous and exothermic process. The results of the equilibrium process study revealed that the adsorption process was physical and desirable. Therefore, the adsorption-desorption process was performed which showed that the composite was reusable up to 20 cycles.

Parametric and kinetic investigations on segregated and mixed textile effluent streams using Moringa oleifera seed powders of different sizes

This study aimed at evaluating the Moringa oleifera (M. oleifera) seed powder for treatment of segregated (dye rich, DR; and starch rich, SR) and mixed wastewater (AM) streams of a textile industry. Two different sizes (<600 μm and <300 μm) of seed powders (coarse powder, CP; fine powder, FP) were prepared and characterized in terms of point of zero charge, swelling ratio, Fourier Transform Infrared Spectroscopy, X-ray diffraction analysis, and zeta potential measurements. The swelling ratio for CP and FP were observed as 38 and 42.6%, respectively. The pHzpc values were found to be varying between 5.5–6 for both powders. The effect of different operational parameters such as dose of coagulant, 1–8 g/L; sedimentation time, 30–360 min; coagulation-flocculation pH, 6–9 was investigated in this study, with respect to turbidity as performance indicator. The chemical oxygen demand (COD) and color measurements were done after the optimization of operational parameters. At optimized pH (DR, 6.5; SR, 7.5; AM, 8.0), the optimum dose of CP and FP were determined as 3, 3, 2 and 3, 2, 1 mg/L for DR, SR, and AM wastewater samples, respectively. With respect to residual turbidity, optimum sedimentation time was observed as 300, 240, 60, 60, 120, and 120 min for DR_CP, DR_FP, SR_CP, SR_FP, AM_CP, AM_FP, respectively. The sedimentation kinetic investigations revealed that turbidity removal follows second-order kinetics for both the studied coagulants. Statistical analysis revealed that CP has the potential of better color and COD removal, as compared to FP.

Effects of Low Frequency-Low Voltage Alternating Electric Current on Apoptosis Progression in Bioelectrical Reactor Biofilm.

Bioelectrochemical systems have undergone several modifications to promote the enzymes or pathways used to reduce the energy required for microbial metabolism. Changes in dominant bacteria, population, and growth rates occur when an electric current is applied intermittently. Applying electricity to bioelectrical reactor (BER) biofilms can either stimulate cells or lead to cell death; therefore, determining the applied voltage range that leads to viable and stimulated bacteria is crucial. We investigated the progression of apoptosis induced by a low frequency-low voltage alternating electric current (AC) in a BER biofilm and found that biofilms on carbon cloth (CC) and stainless steel (SS) 304 electrodes had pHzpc values of 8.67. The pHzpc of the biofilms increased by two compared to that of the inoculant bacteria mass. Furthermore, the Henderson–Hasselbalch equation reveals that the compositions of cell walls of the biofilms that formed on the CC and SS304 electrodes are very similar. In contrast, the CC and SS304 biofilms differ from the inoculant biomass without the influence of an AC field; this indicates that there are differences in the compositions of the cell walls in the present bacteria. Fourier transform infrared spectroscopy was used to compare spectra of the biofilms with that of the inoculation mass, and there were differences in shape and absorbance intensity, indicating variability in the composition, and quantity of each individual biofilm component. In addition, the dehydrogenase activity (DHA) content varied under different applied voltages; the highest DHA was obtained at 8 Vpp. A flow cytometry analysis showed a relatively low number of apoptotic cells (10.93 ± 5.19%) for the AC amplitudes studied. Thus, a low voltage-low frequency AC likely induces significant changes in bacterial metabolic activity but causes no significant change in their viability.

Amorphous phosphated titanium oxide with amino and hydroxyl bifunctional groups for highly efficient heavy metal removal

FAPTO exhibits a low pHzpc value along with abundant amino and hydroxyl bifunctional groups for efficient heavy metal removal from sewage.

Constructing mesoporous phosphated titanium oxide for efficient Cr(III) removal

Heavy metal removal by environmental-friendly nanostructured TiO2 adsorbent is a promising strategy to facilitate wastewater treatment. Here, a boiling water synthetic approach is explored to prepare mesoporous phosphated TiO2 (PTO) used for Cr(III) adsorption in polluted water. We obtain mesoporous 8-PTO (synthesized with 8% molar ratio of H3PO4) with a high specific surface area (278 m2/g), narrow size distribution (<5 nm), low pHzpc (pH of zero point of charge) value (∼1.0), and abundant surface hydroxyl group, which is attributed to the introduction of H3PO4 during the hydrolysis process of TiCl4 in boiling water. Importantly, the obtained 8-PTO shows better thermal stability than pure TiO2 and retains mesoporous structure after thermal treatment owning to [PO4] tetrahedral incorporated into the network of [TiO6] octahedral. The optimized 8-PTO exhibits superior Cr(III) adsorption up to 92 mg/g in sewage, which makes it one of the best materials among TiO2 adsorbent known for Cr(III) Removal (10–83 mg/g). Additionally, the as-prepared mesoporous 8-PTO adsorbent possesses an excellent reusability without significant degradation and can largely avoid the generation of secondary contaminants. A linear relationship (R2 = 0.9985) between adsorption capacity and hydroxyl content percentage of different PTO samples is revealed, indicating that the surface hydroxyl groups play a decisive role in the adsorption process. This study provides a facile approach to synthesize high specific surface area mesoporous phosphated TiO2 with rich surface functional groups for efficient Cr(III) removal in sewage.

Preparation of CoFe2O4/activated carbon@chitosan as a new magnetic nanobiocomposite for adsorption of ciprofloxacin in aqueous solutions.

Ciprofloxacin (CIP) is considered as a biological resistant pollutant. The CoFe2O4/activated carbon@chitosan (CoFe2O4/AC@Ch) prepared as a new magnetic nanobiocomposite and used for adsorption of CIP. CoFe2O4/AC@Ch was characterized by Fourier transform-infrared (FT-IR), field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), vibrating-sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET) surface area measurements. The pHZPC value of the nanobiocomposite was estimated to be 6.4 by solid addition method. The prepared magnetic nanobiocomposites can be separated easily from water by an external magnet and reused. The effect of CIP concentration (10-30 mg/L), adsorbent dosage (12-100 mg/L), contact time (5-30 min) and pH (3-11) as independent variables on ciprofloxacin removal efficiency was evaluated. Optimum conditions were obtained in CIP concentration: 10 mg/L, adsorbent dosage: 100 mg/L, contact time: 15 min and pH: 5. In this condition, maximum CIP removal was obtained as 93.5%. The kinetic and isotherm equations showed that the process of adsorption followed the pseudo-second order kinetic and Langmuir isotherm. The results indicate that the prepared magnetic nanobiocomposite can be used as good adsorbent for the removal of CIP from aqueous solution and can be also recycled.

Removal of Cd (II), Pb (II) and Cu (II) ions from aqueous solution by polyamidoamine dendrimer grafted magnetic graphene oxide nanosheets

Abstract In this study, the as-synthesized magnetic graphene oxide (mGO) nanocomposite was grafted with amine groups, namely the first and second generation of polyamidoamine dendrimer (mGO1st- and mGO2nd-PAMAM) with different oxidation levels and shown to be effective in removing Cd (II), Pb (II) and Cu (II) ions from aqueous solution in batch system. Raman spectroscopy, atomic force microscopy (AFM), Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to identify the structural characteristics of amine functionalized nanocomposites. The pHZPC value of the sorbent was estimated to be 7.2 by titration methods. The different amine functionalization of the mGO stage of the two adsorbents and the differences in the behavior of the three metal ions under magnetic strength were found to be important in order to consider the performance of the adsorption systems. The adsorption capacities of metal ions were 435.85, 326.729 and 353.59 mg g−1 for Cd (II), Pb (II) and Cu (II), respectively. The obtained data were successfully fitted with the pseudo-second-order kinetic model. The adsorption capacity was dependent on the temperature and increased with the increase of temperature. Also, the equilibrium data were evaluated using the Freundlich, Langmuir, and Redlich–Peterson (R–P) isotherm models, suggesting the obtained data were fitted to the Freundlich isotherm model and the adsorption mechanism is heterogeneous. According to thermodynamic analysis, the adsorption process was found to be endothermic and spontaneous in nature. Moreover, the adsorbent was regenerated after a five time adsorption–desorption cycle without significant loss in adsorption capacity. The results from this study support that the as-synthesized adsorbent proves excellent removal ability of the metal ion from water and wastewater.

Photocatalytic activity of V doped ZnO nanoparticles thin films for the removal of 2- chlorophenol from the aquatic environment under natural sunlight exposure

Vanadium doped ZnO powders were used as precursors to deposit thin films of V5+ incorporated ZnO nanoparticles on glass substrates by the pulsed laser deposition technique. The observed variations in Raman signals, visible region shift in the diffuse reflectance spectra along with a small shift in the (101) reflections of the X-ray diffraction (XRD) confirmed the insertion of V5+ ions in ZnO lattice. No other additional reflection in the XRD results other than ZnO further endorsed the occupation of lattice positions by V entities rather than independent oxide formation. The asymmetric XPS peaks of Zn2p and V2p core levels confirmed the existence of both in the vicinity. The existence of minimal proportion of V3+ along with V5+ states varied the alteration of the oxidation states V in the synthetic route. The SEM images at various resolutions displayed the uniform distribution identical nanoparticles without the presence of additional phases in the deposited films. The SEM cross-section measurements revealed the uniform thickness of ∼90 nm of each film, whereas the surface studies of the films were performed by AFM. The as-synthesized films were tested for photocatalytic activity in sunlight illumination for the removal of 2-chlorophenol. The unique feature of the study was the estimation of the photocatalytic activity 20 ppm of 2-chlorophenol by exposing the low exposed area. The degradation of the substrate was measured by liquid phase UV–vis spectroscopy, whereas total organic carbon measurement revealed the mineralization of the substrate. The released Cl− ions were also measured by ion chromatography. The estimated flatband potentials and pHzpc values of the V doped materials, by Mott-Schottky analysis and zeta potential measurements respectively, were correlated with the photocatalytic activity. The kinetics of the photocatalytic degradation/mineralization process was estimated and results were correlated with the plausible mechanism.