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Abstract In recent years, there has been a surge in interest in developing new polymeric materials with high performance and low cost. With increased environmental awareness, research has focused on eco-friendly materials, with terms like “renewable,” “recyclable,” “sustainable,” and “biodegradable” becoming important features of the materials, Polymer blends can provide products with a wider range of useful qualities than single polymer equivalents. In this study, Polymer blend films were prepared using dextrin at different compositions of (PVA- PMMA-PAAm) by solvent casting method. The prepared blend films were flexible and transparent and characterized using was examined by scanning electron microscopy to examine the surface morphology of the samples that show the good distribution of starch in the blend, while FT-IR was used to identify the active groups, which refer to the interaction among the materials. Also, we have studied the optical properties and recording the absorption spectrum with a visible ultraviolet spectrophotometer. Absorption spectra were recorded in the wavelength range of 200–1100 nm. The absorbance and optical conductivity were increased by dextrin additive, while the transmittance and energy gap decreased. Based on the overall results, the prepared films can be used in drug delivery and optical devices.

The agglomeration of rGO resulted from the morphological irregularities restrict its direct applications as catalyst for pollutants removal using advance oxidation processes (AOPs). In this study, we addressed this problem after incorporating the nanosheets of reduced graphene oxide (rGO) in the layers of hydroxides (LDHs) as Fe-rGO LDH hetero-composite. Based on the first order kinetic model, the fabricated composite showed excellent phenol removal with degradation rate constant of 0.16 min−1, 5–100 times higher than Fe-LDH/rGO or other control catalysts. This enhanced catalytic activity was resulted from the systematic assembly of both monolayered rGO and LDHs as superlattice materials, avoiding the aggregation of rGO during the reaction and thus promote the interfacial electron transfer among the active sites. Moreover, Fe-rGO LDH/PMS system exhibited consistent performance over a wide pH range (3.0 ─ 12.0) and broad spectrum of co-existing water constituents (anions and humic acid). The spectroscopic and analytical results suggested that the special arrangement of monolayered rGO in Fe-LDHs facilitated Fe sites to form a stable Fe intermediates after reacting PMS, offering a suitable centre to accept electron from another PMS to generate superoxides (•O2−). Finally, singlet oxygen (1O2) was accounted as dominant reactive oxygen species (ROS) for pollutants removal.

The designing of selective and efficient adsorbent for removal of heavy metals from wastewater of diverse chemistry is a challenging task for researchers. Herein, FeMgAl derived from layered double hydroxides (LDH) with different intercalated anions (CO32−, NO3−, S52− and MoS42−) as selective adsorbents were evaluated by considering capturing heavy metals from a complex aqueous environment such as: 1) adsorption of single metals ions from a mixture of Ag+, Hg2+, Pb2+, Cu2+, Cd2+, Co2+, Ni2+, Zn2+, 2) adsorption of heavy metals in the presence of huge amount of Ca2+, Mg+, Na+, Cl−, NO3− and SO42− ions, 3) adsorption under different solution pHs, 4) solutions with high salinity etc. Out of the studied materials, fast kinetics, record capacities (582 for Hg2+ and 565 mg/g for Ag+) with enormous Kd values (1.0 × 108–2.5 × 107) placed FeMgAl MoS4 (Fe MoS4 LDH) as the most selective and promising material. FeMgAl S5 (Fe S5 LDH) was also impressive due to its good capacities (279 mg/g for Hg2+ and 341 mg/g for Ag+ ions) with Kd values (8.3 × 105–1.0 × 103). In contrast, FeMgAl CO3 and FeMgAl NO3 (Fe CO3 LDH and Fe NO3 LDH) showed very poor selectivity, lower capacities and very small Kd values. Furthermore, Fe MoS4 LDH and Fe S5 demonstrated negligible efficiency loss in the presence of competitive cations/anions or with change in solution pH. As confirmed by X-ray Diffraction (XRD) and Fourier Transformed Infrared (FTIR) analysis, a mechanism for adsorbed metals in the form of various coordinated complexes inside LDH layers was proposed for Fe MoS4 or Fe S5 LDHs. In contrast, a dominant precipitation mechanism as metal-hydroxide or metal-carbonate was suggested for Fe CO3 and Fe NO3 LDHs.

This study proposed a step-by-step oxidation process based on the in-depth analysis of the catalytic mechanism of peroxymonosulfate (PMS) activated by the common MnO2-based catalyst-manganese octahedral molecular sieve (OMS-2). In the first stage, OMS-2-mediated electron transfer dominated the oxidation process. When PMS was completely consumed, the reaction entered the second stage, at which singlet oxygen (1O2) gradually turned into primary oxidation source. OMS-2-mediated electron transfer was proved based on the results of electrochemical analysis, phosphate substitution experiments, and Raman tests. Meanwhile, the oxidation process of 1O2 was unveiled by radical scavenging tests, electron paramagnetic resonance (EPR), and solvent-exchange experiment (from H2O to D2O). Moreover, superoxide radical (O2•−) generated from the reaction between PMS and metastable manganese intermediate was identified as the precursor of 1O2. O2•− generated in the first stage could significantly extend its half-life by adsorbing on the (2 1 1) plane of OMS-2, and then desorbed in the second stage and contributed to the formation of 1O2. More importantly, through the transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and DFT calculations, the essence of step-by-step oxidation driven by O2•− adsorption–desorption process was uncovered.

To meet the current challenges of waste water, an efficient, environment friendly and economical treatment process is always desirable for the degradation of toxic organic compounds. Herein, we reported a stable and active bimetallic CuOx@Co-LDH catalyst for the degradation of phenol using persulfate (PS) under mild conditions. The system of PS/CuOx@Co-LDH completely degraded 0.1 mM of phenol in less than 40 min while at the same time, all the other tested catalysts including catalyst precursors remained sluggish. In view of the practical application, CuOx@Co-LDH/PS system demonstrated consistent performance over a broad pH range (pH 5.0–12.0), during which minimum leaching could be detected. Moreover, good resistance to various inorganic anions was demonstrated in CuOx@Co-LDH/PS system. The consistent performance of CuOx@Co-LDH/PS system may originate from the constant buffer pH of catalyst (9.5 ± 0.8), minimum leaching and the generation of diverse free radicals ( SO4−, OH or − O2) under different pH conditions. Additionally, LDH structure offered strong synergetic interactions among active components which might also help in minimum leaching and good reactivity of CuOx@Co-LDH catalyst. The results of radical scavengers, EPR and XPS studies collectively proved the mechanism of diverse free radicals, which was accounted to the redox cyclic reactions of active sites (Cu(III)–Cu(II)–Cu(III) and Co(III)–Co(II)–Co(III)) during degradation of phenol.

Wide-ranging researches have been executed to treat groundwater from different mining areas, although complex behaviors of diverse metal ion species in the groundwater have not been illustrated clearly. This research study explored the mechanisms through which Pb(II) and V(V) are eliminated in single and binary-metal removal processes by oxygen, nitrogen, and sulfur-doped biochars also considering the kinetic and characterization techniques. The adsorption efficiency of V (V) was enhanced by oxygen-doped biochar at pH 4 with an adsorption capacity of ~70 mg/g. However, Pb (II) was rapidly removed at pH 6 with a higher adsorption capacity of ~180 mg/g by the nitrogen and sulfur-doped biochar forming PbCO3 and V(CO)6 crystals along the single-metal removal process. These results could be explained by the Hard Soft Acid Base theory. The hard Lewis acid vanadium was attracted by the hard Lewis base oxygen, and the intermediate Lewis acid lead was attracted by the intermediate and soft Lewis base nitrogen and sulfur. Besides, the removal ability of Pb(II) and V(V) in the binary-metal removal process showed a similar phenomenon for all types of biochars at pH 4 with the adsorption capacity of ~400 mg/g for Pb(II) and 175 mg/g for V(V), but the composition of vanadium species remains unclear on the surface of the biochars. Initially, H3V2O7−, H2VO4−, and HVO42− species were electrostatically attracted by the oxygen-based functionalities, then V(V) species was partially reduced to VO2+ by the oxygen, nitrogen, and sulfur functionalities in different ratios. Finally, H3V2O7−, H2VO4−, and HVO42− species produced Pb5(VO4)3Cl and Pb2V2O7 which co-precipitate with Pb(II), but VO2+ does not generate any form of precipitates. The above-explained technique supports the treatment of vanadium mining groundwater with valuable vanadinite (Pb5(VO4)3Cl) mineral.

Highly efficient elimination of anionic chromate remains a critical task from the biological and ecological perspective owing to their carcinogenic effects on the biosphere and ecosphere. In literature, varieties of functional materials have been applied to remove Cr(VI) from the environmental sources. In which the chemical reduction of Cr(VI) to Cr(III) by a reductant and simultaneous adsorption of Cr species is an effective technique for the removal of Cr(VI). Many effective reductants were applied in the past years, which could be categorized according to their active functional atom/group. Although very few studies illustrated the complete coordination mechanisms between Cr ions and functional groups during the reduction coupled adsorption. This review focuses on recently investigated Cr(VI) reduction coupled adsorption systems based on the electron donor (reductant) functionalities with the interactions of Cr2O72−, CrO42− and Cr3+ ions by the metal and nonmetal functional groups. Also, the removal capacity and equilibrium time were analyzed based on the findings from isotherm and kinetic studies. To conclude, we offered our insights based on the coordination of chromium species with various functionalities into future research prospects and issues in the hope of motivating more researchers to involve in this new area of functional materials for environmental pollution control.

In this paper, we surprisingly found that the incorporation of unreducible metal oxides MxOy (M = Mg, Zn, Ca, Ba, Al) onto CuO hybrid magnetic nano ferric oxide (Cu@Fe3O4) may alter the reaction pathway in persulfate activation, and increase the reaction rate constant. The activation of peroxymonosulfate (PMS) by Cu@Fe3O4 led to a classic sulfate radical based oxidation process (SR-AOP) with an acetaminophen (ACE) degradation rate constant of 0.004 min−1, while 1O2-dominated nonradical oxidation process was disclosed in CuM@Fe3O4 with wildly fluctuated reaction rate constants from 0.003 to 0.242 min−1. Mechanism studies indicated that singlet oxygen (1O2) derived from the direct oxidation of superoxide anions radicals (O2 −) or the recombination of O2 − was the main reactive oxygen species (ROS) in CuM@Fe3O4/PMS system. A series of characterization experiments (pHpzc tests, XPS, H2-TPR, et al.) and DFT calculation disclosed that the addition of an unreducible metal M yielded many positive effects: (1) the formation of surface oxygen vacancies (OV) raised the zero point charge (pHpzc) of CuM@Fe3O4, thus enhanced the adsorption and activation of PMS; (2) promoting the generation of a new Cu species (Cu3+) on the surface of CuM@Fe3O4, which then participated in the generation of 1O2. The different reducibility of Cu3+ led to differences in the catalytic properties of CuM@Fe3O4. In addition, the effects of various water matrix species and the results of reusability experiment, mineralization experiment, and ecotoxicity test exhibited that CuM@Fe3O4/PMS system possessed excellent practical application value.

Highly efficient magnetic sewage sludge biochar (MSSBC) discloses feasible fabrication process with lower production cost, superior adsorption capacity, usage of waste sewage sludge as resource, selected by external magnetic field and exceptional regeneration property. 2 g L−1 MSSBC exhibited a high adsorption capacity of 249.00 mg g−1 in 200 ppm Pb(II) and the lead-MSSBC equilibrium was achieved within one hour, owing to the existence of the copious active sites. The adsorption kinetics was well described by the pseudo-second-order model while the adsorption isotherm could be fitted by Langmuir model. Mechanism study demonstrated the adsorption involved electrostatic attraction, ion exchange, inner-sphere complexation and formation of co-precipitates at the surface of MSSBC. Additionally, adsorption performance maintained remarkable in a broad pH window. These outcomes demonstrated the promising waste resource utilization by a feasible approach that turns the solid waste of sewage sludge into biochar adsorbent with auspicious applications in elimination of Pb(II) from wastewater.

The development of transition metal based heterogeneous catalysts with efficient reactivity and intensive stability is of great demand in peroxymonosulfate based AOPs in water treatment. Herein, we present a novel approach of creating stable and effective nano-rod catalyst of CuCo@MnO 2 with tetragonal structure. A remarkable synergetic effect was found between bi-metallic oxides of Cu and Co: 0.5%Cu-2%Co-MnO 2 can efficiently degrade 100% of 30 ppm phenol, while 0.5%Cu@MnO 2 or 2%Co@MnO 2 alone is apparently sluggish for the degradation of organic contaminants. The nanocatalyst retained good stability in recycling tests, during which little leaching of Co and Cu ions can be detected and crystallinity of support α˗MnO 2 remained unchanged. Mechanism study indicated that SO 4 − and OH are accounted to participate the degradation, and the generation of radicals is originated from the interaction of CuCo@MnO 2 and PMS through metal site with peroxo species bond. The redox cycle among the active metals (M 2+ ↔ M 3+ ↔ M 2+ ) and Cu enhanced generation of Co(II)–OH complex are critical for the remarkable performance in CuCo@MnO 2 /PMS system. Both the synergetic acceleration of catalyst activity and instinct mechanism are highly suggestive to the design of heterogeneous catalysts for the degradation of organic contaminants in PMS based advanced oxidation processes.

Redox metal ions play the crucial role in versatile advanced oxidation technologies, in which controlling the active species formation through catalyst design is one of the key challenges in oxidant utilization. This work describes an example of different active species formations in CuO-mediated degradation just because of supporting material differences. Although three CuO catalysts were prepared by similar procedures, it was found that CuO-MgO catalyst demonstrated high efficiency in phenol degradation with bicarbonate activated H2O2, in which the superoxide radical is crucial, while hydroxyl radical and singlet oxygen are ignorable. For the CuO-MgO-Al2O3 and CuO-Al2O3 catalysts, the degradation proceeds by popular hydroxyl radical based process, however, the efficiency was poor. The EPR experiments also confirmed the absence of hydroxyl radical in CuO-MgO system but its presence in CuO-MgO-Al2O3 and CuO-Al2O3 system. The high catalytic efficiency with ignorable hydroxyl radical in the CuO-MgO system leads us to propose that an alternative Cu(III) species dominates the degradation. The basic MgO support may facilitate the formation of the Cu(III) species, whereas the neutral MgO-Al2O3 and acidic Al2O3 supports are unable to stabilize the high valent Cu(III) species, leading to the common hydroxyl radical mechanism with low efficiency of H2O2 in alkaline conditions.

Over the past, extensive works executed to treat anionic and cationic heavy metal ions from wastewater. Although very few adsorbents were developed to adsorb anionic and cationic heavy metal ions from the same system. In this study, we explored the pH tunable complete reduction plus adsorption mechanism of Pb2+ and Cr2O72− by dithiocarbamate-based composite. The pH study recommended that; adsorption of Pb2+ occurred at pH 5.5, besides Cr2O72− reduction coupled adsorption executed at pH 3. Furthermore, quick adsorption occurred within 60 min with adsorption capacities of 228.69 and 219.75 mg g−1 for Pb2+ and Cr2O72−, respectively. Adsorption isotherm well described by the Redlich-Peterson model, also adsorption processes were fitted by pseudo-second-order kinetics model. Interestingly, characteristic techniques, a physical monolayer model and thermodynamic models were applied to the experimental results to further understand the adsorption mechanisms. The results indicated that the physical model with two types of interaction energies was more appropriate to interpret the adsorption mechanism. Based on the physical model, three thermodynamic functions were calculated and interpreted to attribute new macroscopic interpretations at the molecular level of the adsorption systems. Inspiringly, the metal-composite system highly effective for 5 regeneration cycles and fixed-bed column could decontaminate 17.2 L of ~10 mg L−1 Pb2+ and 7.3 L of ~10 mg L−1 Cr2O72− to the EPA’s wastewater discharge limit by 5 g of CSC@SDBC with the yielding of 400 and 346 mL of eluent, respectively. Theoretically, a liter of CSC@SDBC column may efficiently adsorb 145,646 mg of Pb2+ and 57,518 mg of Cr2O72− from industrial effluent, these were calculated from the Bohart-Adams model. These collective batch and fixed-bed systems were cost-effective and environmentally tolerable techniques to remove anionic and cationic heavy metal ions from industrial wastewater.

The serious limitations of available technologies for decontamination of wastewater have compelled researchers to search for alternative solutions. Catalytic treatment with hydrogen peroxide, which appears to be one of the most efficient treatment systems, is able to degrade various organics with the help of powerful ·OH radicals. This review focuses on recent progress in the use of bicarbonate activated hydrogen peroxide for wastewater treatment. The introduction of bicarbonate to pollutant treatment has led to appreciable improvements, not only in process efficiency, but also in process stability. This review describes in detail the applications of this process in homogeneous and heterogeneous systems. The enhanced degradation, limited or lack of leaching during heterogeneous degradation, and prolonged catalysts stability during degradation are salient features of this system. This review provides readers with new knowledge regarding bicarbonate, including the fact that it does not always harm pollutant degradation, and can significantly benefit degradation under some conditions.

Black liquor (BL) is an agro-industrial residue with high number of lignocellulosic components which could be recognized as a biomass feedstock. In this work, BL coupled with red mud (RM), were applied to prepare cost-effective zero-valent iron (ZVI) embedded in biochar. The oligomers in BL acted as reductants for RM to generate ZVI, while the organic components could be converted into biochar during pyrolysis. The RM/BL demonstrated excellent performance in the removal of Cr(VI) (349.5 mg/g), as the mechanisms were reduction and adsorption. The fixed-bed column study was conducted and 1.7 L simulated wastewater could be treated by 1.0 g RM/BL. After reaction, 95.5% ± 0.8% and 82.5%±3.2% Cr-loaded adsorbents could be recovered by an external magnet for batch and fixed-bed experiments, respectively. All these results shed light on valorizing these two widespread agro-industrial byproducts, and bridged the knowledge gap between magnetic bio-adsorbent preparation and its industrial practicality on wastewater purification.

It is usually difficult to design selective, stable and efficient adsorbent for the reduction and adsorption of Cr(VI) oxoanions from wastewater. Herein, we report an effective, selective and easily recyclable adsorbent for the elimination of Cr(VI) oxoanions using sulfide assembled hydrotalcite of Fe/Mg/Al hydroxides. Various characterization tools such as XRD, FTIR, SEM, XPS, CHN and ICP were applied to confirm the layered structure and chemical compositions. The prepared adsorbent displayed fast kinetics, high adsorption capacity and outstanding selectivity to Cr(VI) removal. The factors affecting Cr(VI) removal including pH, adsorbent dosage, contact time and initial Cr(VI) concentration was studied. Under the optimum conditions, >99.99% Cr(VI) was removed in 180 min with remarkable distribution coefficients of (Kd > 107). The maximum removal capacity (135.59 mg/g) placed the prepared adsorbent on the top of materials list known for Cr(VI) removal. Pseudo-second-order kinetic model expresses well the adsorption behavior towards Cr(VI), indicating a chemisorption process, while the sorption isotherm agreed with the Langmuir model, suggesting monolayer adsorption. The ( S )2− in MoS42− was involved in reducing Cr(VI) to Cr(III) while itself simultaneously being oxidized to SO42− and the redox reaction was evidenced by XPS analysis. Moreover, due to the unique memory effect of layered double hydroxides, significant stability and excellent reusability were also achieved. Based on the results obtained, hybrid adsorbent by embedding sulfide into hydrotalcite of Fe/Mg/Al hydroxides can be considered as one of a compelling candidate for the remediation of hexavalent chromium.

We have successfully synthesized chromium doped gamma ferrite (γ-Fe2O3) nanopowders (16.9 nm to 25.6 nm) of the composition (Fe2−xCrxO3 for x = 0.00, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10) by a slightly modified solution combustion method using citric acid as fuel at considerably low temperature. The so prepared powders were extensively studied for complex permeability and optical behaviour. It was found that Cr3+ doped γ-Fe2O3 has significant permeability values and it can therefore be used as a high permeability core material and in Multi-layer Chip Inductor (MLCI) applications in electronic products, such as cellular phones, computers and video cameras. The results obtained in terms of permeability spectra suggest that γ-Fe2O3 and its doped variants when made in nano-form behave as a high permeability material at ultra high frequencies (5–25 MHz) with permeability showing unusual inverse dependence on the grain dimension. Optical studies of the material confirm the presence of two band gaps BGd1 and BGd2 falling within the solar energy spectrum, thereby making this material a promising candidate for single junction photovoltaics with enhanced power conversion efficiency. We have also shown that the nano-sized γ-Fe2O3 synthesized by cost effective and modified sol–gel auto-combustion technique can be a good alternative to highly mismatched alloys (HMAs).

Dielectric relaxation and electrical properties of Al doped polycrystalline bismuth ferrite (BAFO) nano-structured ceramics (13–20 nm having composition Bi 1− x Al 2 x Fe 1− x O 3 (0.0 ≤ x ≤ 0.3) were investigated over a wide range of frequency and temperature. Relaxation peaks were obtained in low as well as high frequency regions for all samples which are explained on the basis of Debye-type relaxation model. The replacement of Fe 3+ and Bi 3+ by Al 3+ ions in the BFO system creates oxygen vacancies and hence Schottky barriers, which are responsible for the anomalous behaviour in the dielectric properties. Debye relaxation model and Maxwell–Wagner charge carriers hopping were utilized in overall estimation of the dielectric behaviour of the system. The values of dielectric constant and loss tangent were found to decrease with the increase in frequency, while these parameters increase with the increase in temperature as well as dopant concentration. The a.c. conductivity has a general decreasing trend as a function of composition while it increases with the increase in frequency. The temperature dependence of a.c. conductivity and relaxation time follow well-defined Arrhenius behaviour. The calculated values of activation energies are in the order of 0.54 eV–0.73 eV ( 2− vacancies.

Aluminum doped Bismuth ferrite (BFO) nanopowders (grain size 13–20 nm) having composition Bi 1− x Al 2 x Fe 1− x O 3 ( x = 0.00, 0.025, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) were successfully synthesized by solution combustion method using citric acid as fuel at a temperature as low as 200 °C. As-prepared samples were examined by powder XRD for phase identification and crystallite size determination. The d.c. resistivity as a function of temperature was measured by standard two probe setup which exhibits clear metal to insulator transition for all samples. FTIR analysis was carried out to identify the chemical bonds present in the system. The optical band gap was calculated from the UV–vis absorbance spectra using classical Tauc relation which was found to vary from 2.78 eV to 2.93 eV for different Al 3+ concentrations. The activation energies calculated from the slopes of ln( ρ ) versus 10 3 / T plots are in the range 0.54–0.73 eV.

Conditions are described by which a group of up to ten sulfonamide drugs, namely, (1) sulfanilamide, (2) sulfaguanidine, (3) sulfacetamide, (4) sulfathiazole, (5) sulfamethoxydiazene, (6) sulfamethoxypyridazine, (7) sulfamethazine, (8) sulfadimethoxine, (9) sulfapyridine, and (10) sulfadiazene, in admixture, may be separated by thin-layer chromatography. Each drug can be identified qualitatively and determined quantitatively by pyrolysis-gas chromatography. Each separated zone is cut from the plate and pyrolysed at 780°C in a stream of nitrogen gas in a continuous mode pyrolyser designed in this laboratory. The pyrolysis products are separated on Tenax TA in a glass column held at 210°C and the amount of drug related to the aniline peak height as determined by the flame ionization detector. Linear calibration curves for up to 6 μg of drug were obtained for drugs 1 to 8 and up to 4 μg for 9 and 10.