Effect Of Initial Dye Concentration Research Articles

Highly efficient and selective removal of anionic dyes from aqueous solutions using polyacrylamide/peach gum polysaccharide/attapulgite composite hydrogels with positively charged hybrid network

To avoid the weakness (lower adsorption rate and selectivity) of peach gum polysaccharide (PGP) and improve the adsorption performance of polyacrylamide (PAAm) hydrogel (lower adsorption capacity), in the present work, the PGP was chemically tailored to afford ammoniated PGP (APGP) and quaternized PGP (QPGP), and attapulgite (ATP) was bi-functionalized with cation groups and carbon‑carbon double bond. Then, PAAm/APGP and PAAm/QPGP/ATP hydrogels were synthesized via redox polymerization. The synthesis procedure and properties of hydrogels were traced by FTIR, SEM, XPS, TGA, TEM, and BET methods, and the dye adsorption performance of the hydrogels was evaluated using the new coccine (NC) and tartrazine (TTZ) aqueous solutions as the model anionic dyes. Effects of initial dye concentration, pH, and ionic strength on the adsorption were investigated. Compared with PAAm/APGP hydrogel, PAAm/APGP/ATP hydrogel exhibits higher adsorption rate, superior adsorption capacity, stability, and selectivity towards anionic dye. The adsorption process of PAAm/QPGP/ATP hydrogel reached equilibrium in about 20 min and followed the pseudo-second-order kinetic model and Langmuir isotherm. The adsorption capacities towards NC and TTZ of PAAm/QPGP/ATP hydrogel were calculated as 873.235 and 731.432 mg/g. This hydrogel adsorbent originating from PAAm, PGP, and ATP shows great promise for application in practical water treatment.

Investigation and Optimization of Biosorbent Capacities of Some Plants Used in Daily Life

In this study, sage, chamomile, and tarragon leaves, which are used as spices and consumed as beverages in daily life, were considered as different biosorbents that can be used in water purification by biosorption. At the same time, the effects of the parameters of initial dye concentration (10-200 mg/L), temperature (20-50 ⁰C) and contact time (0-120 min) on biosorption capacity were investigated. The biosorption processes were found to follow Freundlich isotherm and pseudo-second order (PSO) reaction kinetics. In the study, the process was also modeled using multi-tree evolutionary computation based automatic programming (AP) methods. The methods used initial dye concentration, temperature, and contact time as variables. According to the simulation results, these methods obtained nonlinear mathematical models of the processes with R^2 values as high as 0.99 for each biosorbent. By providing the most accurate models to accurately predict biosorption capacity, this study will make a significant contribution to the field of water treatment using experimental and AP methods.

Utilization of aquatic biomass as biosorbent for sustainable production of high surface area, nano- microporous, for removing two dyes from wastewater

The majority of environmental researchers are becoming increasingly concerned with the manufacture of inexpensive adsorbents for the detoxification of industrial effluents. To address one of the significant and well-known pollution issues with certain drains that act as hotspots and contribute to coastal pollution in Alexandria, this study aims to develop an economical, ecologically friendly sorbent. This study assessed the efficacy of a biomass-coated magnetic composite and a magnetic active adsorbent for the removal of two dyes from an industrially contaminated sewer using a wetland plant (Phragmites australis). Using magnetic biosorbent, the biosorption of Xylenol orange and Congo red ions from polluted drain discharge in Abu Qir Bay was evaluated in the current study. Using scanning electron microscopy imaging and Fourier transform infra-red analysis; the surface function and morphology of the nano-biosorbent were examined. At room temperature, the effects of initial dye concentration, pH, contact time, and nano-biosorbent concentration have all been investigated. The greatest percentages that nano-biosorbent can remove from Congo red and Xylenol orange are 97% and 47%, respectively. The removal of the initial Congo red concentration varied from 42 to 97%, while the removal of the initial Xylenol orange concentration varied from 30 to 47%. The adsorption capacity was shown to be strongly pH-dependent; capacity dose as pH value increased, with pH 10 being the ideal pH for Congo red and pH 6 being the ideal pH value for Xylenol orange. The adsorption capacity for Congo red varied between 0.96 and 3.36 and the adsorption capacity for Xylenol orange varied between 0.18 and 17.58. The removal capacity decreased from 3.36 to 0.96 mg/g when the biosorbent dosage was increased from 0.05 to 0.5 g/L for Congo red, in case of Xylenol orange, the removal capacity increased from 0.18 to 17.58 mg/g when the biosorbent dosage was increased from 0.05 to 0.5 g/L. The removal capacity of Congo red increases quickly with time and varied from 1.66 to 1.88 of contact time; while the removal capacity of Xylenol orange varied between 3.08 and 4.62 of contact time. For the dyes under study, kinetics and adsorption equilibrium were examined. Within 180 min, the equilibrium was attained because to the quick adsorption process. For Congo red and Xylenol orange, the highest adsorption capacities were 3.36 and 17.58 mg g−1, respectively. The equilibrium data were assessed using a number of isotherm models, including Langmuir, Freundlich, BET, and Tempkin, while the kinetic data were examined using a variety of kinetic models, including pseudo-first- and pseudo-second-order equations. The pseudo-second-order equation provides the greatest accuracy for the kinetic data and Langmuir model is the closest fit for the equilibrium data.

Adsorption kinetics behavior of MB dye on CaO nanosheets

The work reported herein demonstrates the fabrication of CaO nanosheets employing a thermal decomposition method. The obtained CaO nanosheets were characterized using TEM, BET, XRD, EDX, and FTIR instruments. Moreover, the effect of initial dye concentration and pH on MB removal by CaO nanosheets was studied. The result showed that the nanoparticles have sizes around 100 nm, and the CaO nanosheets have an average diameter of 50 nm. Meanwhile, the average pore diameter and surface area of CaO are 15.847 Å and 5.881 m2. g−1 , respectively. Numerical models based on Temkin, Freundlich, and Langmuir were applied to adsorption data to better understand the MB dye adsorption onto CaO nanoparticles. The sorption findings demonstrated a stronger fit with the Temkin model (R2 = 0.983) compared to the Freundlich model (R2 = 0.947) and Langmuir model (R2 = 0.968). The maximum adsorption capacity of MB on the CaO nanoparticles is 688.01 mg/g. The investigation determined that the adsorption kinetics adhered to the Pseudo-second-order kinetic model(R2 =0.982).

Hydroxypropyl sulfonated starch and Asperlligus oryzae biomass for cationic dye adsorption: characterization, mechanism, sorption modelling

AbstractIn this work, hydroxypropyl starch sulfate (HPSS) and Aspergillus oryzae (Asp. oryzae) were successfully synthesized and investigated for aqueous methylene blue (MB) adsorption. The as-prepared adsorbents were also characterized extensively using FTIR, XRD, SEM, EDX, and BET surface area analyses to elucidate their functional, textural, and morphological properties. Also, the effects of initial dye concentration, contact time, and pH on the adsorption performance of both adsorbents were systematically investigated. Due to the significant surface area differences, the HPSS recorded a higher maximum adsorption capacity (qmax) of 52.41 mg/g at 20 mg/L initial concentration, 60 min, and pH 8.0, while the Asp. oryzae recorded a qmax of 37.26 mg/g at 20 mg/L initial concentration, 60 min, and pH 9.0. Specifically, the –SO3 groups on the HPSS shared some electrostatic affinity with the MB dye cationic center (N+ backbone), while a hydrogen bond is formed between the hydroxyl groups of the starch and N+ backbone of the MB dye. Also, the nitrogen- and oxygen-containing groups on the Asp. oryzae provided active sites for the binding of MB species. Also, the XRD spectra of the loaded HPSS showed a decrease in the sharp crystalline peaks, while no structural changes were observed in the case of loaded Asp. oryzae. Therefore, the effectiveness of the HPSS and Asp. oryzae for adsorbing MB was established in the study.

Influence of the prepared activated carbon on cellulose acetate for malachite green dye removal from aqueous solution

Guava (Psidium guajava) seeds were used for the preparation of activated carbon (AC) activated using zinc chloride (GCZ36), phosphoric acid (GCH36), potassium hydroxide (GCK36), and one other sample was prepared without activation (GC36), carbonized for 3 h at 600 °C. They were added to cellulose acetate to form hybrid membranes (Ms) using the phase inversion technique. The prepared AC was characterized by % ash content, % weight loss on drying, nitrogen adsorption isotherm, TEM, and XRD. FTIR and SEM were used for the ACs and Ms. GCK36 sample exhibited a higher surface area (905.27 m2/g) and total pore volume (0.5360 mL/g). The hybrid membranes were used to remove malachite green dye (MG) from wastewater. The effect of initial dye concentration, adsorbent dosage, pH, and contact time were studied. Pseudo-first-, pseudo-second-order, and intraparticle diffusion rate equations were proposed and the kinetic data were analyzed. Maximum adsorption capacity (31.82 mg/g) was achieved after 100 min, at pH 6 and 0.25% AC. The adsorption capacity of the cellulose acetate membrane was increased by 111.7% using the prepared activated carbon. The results indicated the chemisorption process and the adsorption was fitted to Langmuir > Freundlich > Tempkin due to R2 values.Graphical abstractSchematic diagram of preparation of a composite membrane of cellulose acetate and guava seeds activated carbon

Raw Smectite from the Guarapuava–Parana–Brasil Saturated with Copper Ions and Its Properties

In this study, raw smectite (Sm), from the Guarapuava–Parana–Brasil region, was saturated with copper ions (Cu-Sm) by ion exchange and the samples Sm and Cu-Sm were used in crystal violet (CV) adsorption and applied as an antimicrobial and antifungal hybrid pigment. Samples (Sm and Cu-Sm) were used to remove crystal violet (CV) dye from aqueous media, simulating wastewater. Samples after use as adsorbents were characterized and named smectite/adsorbed dye (Sm/Dye) and copper smectite/adsorbed dye (Cu-Sm/Dye); and they were applied as hybrid pigments with antimicrobial action. The Sm and Cu-Sm were characterized by X-ray diffractometry (XRD), energy dispersive X-ray fluorescence (EDXRF), vibrational spectroscopy (FTIR), Zeta potential (ζ), scanning electron microscopy (SEM), and colorimetry (CIE L*a*b*), enabling the identification of the presence of intercalated copper ions and on the smectite surface. The adsorption assays were carried out to evaluate the effects of initial dye concentration and contact time. Tests for application as a hybrid pigment showed good compatibility with commercial white paint being applied on plaster blocks and later photoaging and chemical stability tests were performed in acid and basic environments, both were discussed by colorimetry (CIE L*a*b*), thus being able to relate it to the color variation (∆E). The samples (Sm, Cu-Sm, Sm/Dye, and Cu-Sm/Dye) were dispersed in white paint at 10% and 20% (% w/w) to evaluate the ability to inhibit different microorganisms. The modification with copper ions promoted an increase in the adsorptive capacity relative to the raw smectite and provided antibacterial and antifungal action to the hybrid pigment against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Candida albicans. The Cu-Sm and Cu-Sm/Dye samples showed excellent results against all studied microorganisms and reveal successful materials that can be used in environments that require microbiological protection.

Synthesis and characterization of Ag doped ZnO nanomaterial as an effective photocatalyst for photocatalytic degradation of Eriochrome Black T dye and antimicrobial agent

Doped ZnO nanomaterials are a type of material that can be used for photocatalysis and antibacterial applications. The metal dopant improves the overall performance of the photocatalyst by lowering the band gap energy and lowering electron–hole recombination. Likewise, metal dopants result in a significant increase in antimicrobial potential. Premised on these compelling viewpoints, we present a straightforward co-precipitation approach for synthesizing ZnO and 5% Ag modified ZnO (5% Ag/ZnO), as well as their applicability in photocatalysis and antibacterial study. The synthesized ZnO and 5% A/ZnO nanomaterials are well characterized by Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. From the UV-Vis analysis, it has been established that silver doping resulted in a decline in the band gap of ZnO. The XRD investigations indicated hexagonal wurtzite structure for ZnO and 5% Ag/ZnO with average nanoparticle sizes of 25.37 and 20.23 nm, respectively. The porous morphology of produced nanomaterials was shown by FE-SEM analysis, while the elemental composition was validated by EDAX. The ZnO and 5% Ag-ZnO were successfully employed for the photocatalysis of Eriochrome Black T (EBT) dye and antimicrobial screening. Various parameters like catalyst dose, the effect of contact dye, and the effect of initial dye concentration were investigated which proved that 5% Ag/ZnO is more proficient in the degradation of EBT dye than ZnO. Besides, the radical scavenging study was to explore the presence of reactive oxygen species in photocatalytic degradation. The kinetic study revealed the involvement of Pseudo first-order kinetics. Furthermore, the 5% Ag/ZnO was recycled and reused for multiple cycles which indicated its stability and reusability performance. The antibacterial studies of ZnO and 5% Ag/ZnO against S.aureas, B. subtilis, K. pneumoniae and E. coli and antifungal studies against A. niger and C. albicans were investigated. The antibacterial and antifungal screening clearly emphasized that silver doping has an excellent effect on the augmentation of the antimicrobial performance of ZnO.

Utilization of metal industry solid waste as an adsorbent for adsorption of anionic and cationic dyes from aqueous solution through the batch and continuous study.

Industrial waste, for instance, textile effluents when released into the ecological system without first being treated or with inappropriate levels of treatment, can lead to serious issues deteriorating the environment and human health. Moreover, solid waste from various industries has also become a major issue due to massive urbanization. For instance, the waste from the metal industry has been rapidly increasing such as Jarosite which has various metals, metal oxides, and silica in its composition. Therefore, Jarosite was utilized as an adsorbent for the adsorption of anionic Congo red (CR) and cationic Methylene blue (MB) dyes from aqueous solutions. The processed adsorbent sample was characterized by BET, XRD, SEM, EDS, FTIR, and XPS techniques. The effects of initial dye concentration, pH, adsorbent dose, temperature, and contact time were examined. The metal industry waste is used as a low-cost abundant adsorbent with great potential for adsorption ability to remove the CR (97.5%) and MB (68.5%) at pH 7, contact time 90min, adsorbent dose 0.1g, and initial dye concentration 50mg/L. The adsorption data followed the adsorption isotherm and Kinetics for both dyes. The removal of both dyes was a physical adsorption process, endothermic and spontaneous reaction. Column adsorption investigation was described by AB (Adams-Bohart) and YN (Yoon-Nelson) models. According to the economic view, the utilization of jarosite for dye removal is a cost-effective approach, because it is collected free of cost from industries. Henceforth, for the first time, toxic metal industry waste was successfully utilized as an adsorbent for wastewater treatment.

Degradation of magenta dye using cavitation-based transducers to glass marble: Lab to semi-pilot scale operations.

In the present work, the degradation of magenta dye has been investigated using ultrasonic (US) and ultraviolet (UV) irradiation at a laboratory scale. Additionally, the investigation was conducted at a semi-pilot scale by employing hydrodynamic cavitation and a novel air-marble cavitation reactor. Initially, optimization studies such as the effect of initial dye concentration and catalyst loading of TiO2 and MnO2 followed by the effect of combined catalyst loading (TiO2 /MnO2 ) on the extent of degradation have been studied at a capacity of 3 L. It was observed that the US irradiation results in 87.1% and 68.2% of degradation, whereas the UV irradiation results in 79.8% and 56.4% extent of degradation at 1 g/l of TiO2 and 0.8 g/l of MnO2 , respectively. The maximum degradation was 92.1% at the combined loading of 0.6 g/l (1:0.8; TiO2 :MnO2 ) using US irradiation with a capacity of 3L and 81.3% using a hydrodynamic cavitation reactor with a semi-pilot scale capacity of 7L. The chemical oxygen demand (COD) analysis also showed the highestCODremoval of 92% at a small scale using the US irradiation and 76% at a semi-pilot scale using hydrodynamic cavitation. On a small scale, the cost of a US/TiO2 + MnO2 treatment scheme is US$ 0.01/L, whereas on a semi-pilot scale using HC/TiO2 + MnO2 , the cost is US$ 0.04/L. Both of these treatment schemes offer viable pathways for degradation based on energy and economic assessments. Overall, the current work has clearly demonstrated the effectiveness of the cavitational reactor for the efficient degradation of magenta dye from lab to semi-pilot scale operation. PRACTITIONER POINTS: Small-scale dye containing wastewater treatment using ultrasound and ultraviolet irradiation Combined use of catalysts at large-scale operations with novel cavitation techniques Novel cavitation techniques studied for dye degradation. Energy efficiency and cost analysis evaluated for AOPs studies.

Integrated Adsorption and Photocatalytic Degradation of Malachite Green Using Carbon Based Nanocomposites (ZnO-AC)

Malachite green dye is widely used in dye industries, aquaculture industries and food industries. The prevalence of this malachite green in the effluent of wastewater could potentially harm human health and destroy the aquatic system. Hence, to completely destroy its presence in the effluent, a technique of integrated adsorption and photocatalytic degradation was introduced. Integrated photocatalyst adsorbent (IPCA) utilizing zinc oxide as photocatalyst and supported on activated carbon derived from melinjo shell, ZnO-AC was synthesized. Activated carbon derived from the melinjo shell provides a porous surface for adsorption while zinc oxide is sensitive to photons and enhances better light absorption. ZnO-AC was subjected to scanning electron microscope (SEM) and Fourier Transform infrared spectroscopy (FTIR) characterization. The analysis revealed a porous sponge network and an intense peak of zinc oxide at 650-700 cm−1. The performance of ZnO-AC was evaluated by studying the effect of initial dye concentration (10-50 ppm), pH (2-11) and ZnO-AC dosage (5-25 mg) in the presence of UV light. In this study, the optimum conditions for dye degradation were found to be 10 ppm initial dye concentration, pH 11 and 15 mg ZnO-AC dosage. Kinetic behaviour of the dye degradation was also investigated. The photocatalytic degradation followed Langmuir-Hinshelwood model and the data corresponded well with pseudo-first-order kinetics.

Mechanochemical route for carboxy substituted Schiff-Base polymer coated MWCNT composite as an efficient adsorbent for the removal of Methylene Blue dye: Kinetics, Isotherms and Thermodynamic studies

In the present investigation, we report a rapid and green mechanochemical approach for the synthesis of carboxy substituted Schiff-Base polymer (cPSB) and MWCNT coated with cPSB composite (cPSB@MWCNTs) as an efficient adsorbent for cationic methylene blue MB dye. The as-synthesized cPSB and cPSB@MWCNTs were characterized by Fourier-transformed infrared spectrometer (FTIR), X-ray diffraction (XRD) and Scanning electron microscopy (SEM) to analyze the structure, size and morphology. Effects of different variables such as catalyst loading, contact time, effect of initial dye concentration and pH of the medium during the process of dye adsorption were studied. Adsorption was in agreement with the pseudo-second-order and is a chemisorption process according to the kinetic analysis. The adsorption equilibrium data for the dye adsorption process fitted well with the Langmuir model. In cPSB@MWCNTs, the removal efficiency of MB was found to be 99 % in 90 min at pH 7. The adsorption of dyes on cPSB@MWCNTs from thermodynamic data was found to be spontaneous and endothermic with a continuous decrease in entropy. Further cPSB@MWCNTs composite demonstrated admirable maximum adsorption capacity towards both MB (96.9 mg g−1) indicating cPSB@MWCNTs as an efficient cationic dye adsorbent.

Solar expedited photodegradation of orange-g using H2O2

Decolourisation and degradation of azo dye Orange G was carried out by using the solarassisted photodegradation process using H2O2 and the effect of various parameters on decolourisation and degradation were analysed. Dye solutions of concentration 100 mg/L treated with 30% H2O2 were taken in 250 ml conical flasks and they were exposed to sunlight in the lux intensity range of 60,000 to 90,000 lux to study its decolourisation and degradation. Effect of various parameters on decolourisation and degradation of dye like the effect of initial pH, the effect of initial H2O2concentration, the effect of initial dye concentration, the effect of additives like chloride and dihydrogen phosphate of concentration 1 M, the effect of solar light intensity, the effect of temperature were studied as kinetic studies. Optimum pH was found to be 11 and optimum H2O2 concentration was found to be 250 mM to achieve 100 % decolourisation of the dye within the shortest time duration of 1.5 hours. Kinetic studies done on the effect of pH and the effect of H2O2 concentration also provided evidence for that. Effect of chloride ion has lead to enhancement in the rate of decolourisation whereas addition of dihydrogen phosphate ion inhibits the rate of decolourisation. An increase in solar light intensity has lead to increase in the rate of decolourisation. An increase in temperature has lead to increase in the rate of decolourisation. UV spectrum was taken for the dye and degraded dye to study the extent of degradation of the dye. COD and TOC removal were also studied to know about the mineralisation of the dye.

Synergistic adsorption-photocatalytic degradation of Rhodamine B dye using a 3D-printed photoreactor with g-CN homojunction-based thermosets coating: response surface methodology and adsorption modelling

In present work, graphitic carbon nitride (g-CN) homojunction were synthesized to investigate the synergistic effect of photocatalysis and adsorption on Rhodamine B (RhB) dye degradation. The photodegradation (DE%) and adsorption (R%) were evaluated under the irradiation of two 50 W LED lights and in dark for 6 hours, respectively. A three-level Box-Behnken design (BBD) were employed to study the effects of initial dye concentrations (5 to 20 ppm), recirculation flow rates (1 to 3 mL/min), and the number of photoreactors (2 to 6) with total 15 sets of experiment. A quadratic regression was developed to predict DE% with an error of less than 5.5% relative to the experimental data. Additionally, ANOVA analysis showed that the number of photoreactors is the most influential parameter (p<0.05); while the two-way interaction between variables are insignificant. For the adsorption studies, Langmuir isotherm showed the best-fit result (R2>0.98) and the separation factor (RL) has indicated the adsorption process is favourable (RL=0.05). Additionally, the adsorption experimental data fit well with the pseudo-second-order kinetic model (R2>0.98). Overall, the development of homojunction photocatalyst has provided an innovative and alternative approach for water remediation.

Sono-synthesis of cellulose-TiO2 nanocomposite adsorbent for fast cleaning of anionic dyes containing wastewater

This work was devoted to synthesizing a composite of cellulose-TiO2 by the in-situ process using the sol-gel method and applied on representatives of acid dyes to determine the functionality regarding the adsorption of dyes from aqueous solution. The composite particle adsorbed 100% dyes within 3 min of the direct application. XRD, FTIR, SEM, and Zeta potential tests were conducted to investigate the effect of crystal, molecular structure, surface morphology, and surface charges on the absorption speed of cellulose-TiO2 composite particles. The experimental results revealed that the cellulose was partially hydrolyzed by concentrated hydrochloric acid and left some positive charge on the surface of cellulose during the synthesis of the composite structure. The test results demonstrated that nano TiO2 with a thin layer of cellulose covered the surface of undegraded cellulose particles. The structural changes in the composite made them beneficial to fast dye adsorption. The effect of initial dye concentration, composite dosage, and temperatures were also investigated to find the optimum condition for dye adsorption. The optimum condition was found at the initial concentration of 400 mg/l, dosage of 0.10 g, and temperature of 25 °C. The removal efficiency and maximum adsorption capacity at this condition were 100% and 40 mg/g, respectively. The adsorption data suggested that the data was well fitted with a pseudo-second-order model for adsorption kinetics and Langmuir model for adsorption isotherm. Thermodynamic analysis revealed that the adsorption process was physisorption, spontaneous, random, and endothermic. Overall, in this work, the developed cellulose-TiO2 nanocomposite might be an economical and efficient adsorbent to remove dyes from wastewater.

PHOTODEGRADATION OF METHYL GREEN (MG) ON NANO COMPOSITES OF SnO2, Cd/SnO2 AND AC - Cd/SnO2 UNDER UV LIGHT

Nanocomposite of activated charcoal supported cadmium doped SnO2 were synthesized by precipitation method and the physicochemical properties of the compounds were characterized by various technique. These nano-composites were used for photo catalytic degradation of methyl green (MG) organic dye under UV light irradiation at room temperature. Effect of de-coloration, Effect of the amount of catalyst, Effect of reusability, Effect of pH, effect of initial dye concentration, on the rate of photo-degradation was investigated also discussed photo-degradation mechanism of methyl green(MG) organic dye

Synthesis of Fibrous Micro-nano Hierarchical Porous Cerium Dioxide Materials by the Impregnation and Thermal Decomposition Method and Its Enhanced Photocatalytic Activity

Fibrous micro-nano hierarchical porous cerium dioxide materials were prepared from oriental paperbush flower stems by impregnation and thermal decomposition methods. Thermogravimetric analyzer (TG, DSC), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption isothermals, temperature-programmed reduction (TPR), and UV-Vis spectrophotometer were used to characterize the thermal decomposition behavior, microstructure and photocatalytic properties of fibrous micro-nano hierarchical porous cerium dioxide materials. The results proved that the achieved products retained a fibrous morphology similar to oriental paperbush flower stems with the original biotemplate in material completely removed. The average diameter of CeO2 particles on the surface of the material is about 9 nm, and the large specific surface area is around 55.6 m2/g. UV-Vis absorption spectra showed that the fibrous micro-nano hierarchical porous cerium dioxide materials have high light absorption capacity and can respond to simulated sunlight. The effects of initial dye concentration, catalyst concentration, pH value, cycle number, and irradiation time on the photocatalytic activity of fibrous micro-nano hierarchical porous cerium dioxide materials for the photo-degradation of methylene blue under simulated solar irradiation were systematically studied. A reasonable photocatalytic mechanism is proposed based on the experimental results and theoretical analysis. This strategy can be extended to synthesize other broad bandgap semiconductor oxides with high photocatalytic activity for the photo-degradation of organic dyes under simulated solar irradiation.

Study of methylene blue dye elimination from water using polyaniline (PANI) and PANI/SiO2 composite

Conducting polymeric composites have attracted great attention over the last years because of their potential uses in chemical, electronic and optical devices, and as catalysts as well as in adsorption processes. Chemical synthesis of polyaniline (PANI) and polyaniline-SiO2 composite and their adsorptive performance were reported in the present work. These materials were prepared and evaluated for their methylene blue (MB) dye adsorption characteristics from aqueous solution. Adsorption equilibrium kinetic and thermodynamic experiments of MB onto PANI and PANI/SiO2 were studied. The effects of initial dye concentration, contact time and temperature on the adsorption capacity of PANI/SiO2 for MB have been investigated. The pseudo-first order and pseudo-second order kinetic models were used to describe the kinetic data. It was found that adsorption kinetics followed the pseudo-second order at all of the studied temperatures. The Langmuir, Freundlich and Dubinin Raduschkevich adsorption models were used for the mathematical description and the HyperChem v8 software was exploited to propose a possible mechanism of the adsorption process.

Insights into the role of metal cation substitution on the anionic dye removal performance of CoAl-LDH

The preparation of the adsorbent plays an important role in the adsorption technology, especially the selection of adsorbents with high specific surface area and special structure is particularly critical to the entire adsorption process. Herein, a series of ternary LDHs was designed via a facile hydrothermal method, and in another word, all derived from binary CoAl-LDH by substituting with another transition metals(Ni, Zn, Fe), used as adsorbents to remove MO and CR. The adsorption capacity of the obtained ternary LDHs are better than that of the pristine CoAl-LDH, and CoNiAl-LDH stands out with the higher adsorption capacity than other ternary LDHs samples whether the dye is MO or CR. Then the effect of initial dye concentration, pH and temperature on its MO adsorption performance was systematically studied. The maximum adsorption capacity reached more than 330 mg/g under the optimal conditions (25 °C, pH=3). This work may provide a method to design the advanced adsorbents design for further enhancing the adsorption activity in the field of water environmental protection.

Photocatalytic Oxidation of Acid Orange 10 dye Molecules using Cerium Oxide Nanosphere Particles under Ultraviolet and Visible Light Irradiations

Exploration of semiconductors in the field of photocatalysis plays a crucial role in energy and environmental remediation in particular oxidation/reduction of toxic organic contaminants from water and wastewater. The present research work aims on synthesis of pristine CeO2nanoparticles by precipitation method and was thoroughly characterized by Fourier Transform Infrared spectroscopy, X-ray Diffraction, UV-vis-Diffuse Reflectance Spectroscopy, High Resolution Scanning Electron Microscopy, EDAX and Electron Spin Resonance techniques. The band gap energy (Ebg) was found to be 3.19 eV. The synthesized nanomaterials showed spherical morphology and the particles size ranged from 50-93 nm. The insitu generation of ·OH radicals was confirmed from ESR studies. The synthesized CeO2nanospheres was evaluatedin photocatalytic oxidation of an azo dye Acid orange 10 under Ultraviolet and visible light irradiations. Experimental studies such as pH, catalyst amount and effect of initial dye concentration were also studied. Kinetic studies indicate the photo reaction follows pseudo-first order rate equation. The photocatalytic oxidation of dye molecules were monitored by UV-visible spectroscopy and COD analyses. The level of chemical oxygen demand (COD) of the photodegraded samples decreases in both the photocatalytic systems indicating that dye molecules readily degraded under present experimental conditions.Effect of electrolytes like MgSO4,KCl, Na2CO3 and NaHCO3 were also investigated to check interference of inorganic anions on photocatalytic oxidation of dye molecules using CeO2 nanospheres. Finally, the prepared catalyst was checked for its reusability and the photocatalyst exhibited better photocatalytic activity evenafter three cycles of regeneration.Copyright © VBRI Press.