Pseudo-first Order Kinetic Model Research Articles

Adsorptive Desulfurization of Model Fuel by Modified Activated Carbon

The purpose of this study was to identify the effect of modified activated carbon (MAC) on the adsorption isotherms and kinetics of dibenzothiophene (DBT) removal in a model fuel. In this study the commercial activated carbon (AC) was modified by chemical treatment with nitric acid (HNO3) followed by adsorption experiments with different concentrations and contact times. The MAC was characterized using Fourier-transform infrared spectroscopy (FTIR) to identify changes in the MAC functional groups. A broad and intense peak at 3471.53 cm-1 for MAC was detected which indicates the stretching vibration of the O–H bond. After adsorption, the solution was analysed using ultraviolet-visible (UV-vis) light spectroscopy. In this study, the amount of DBT adsorbed by the MAC was in the range of 46.8% to 68.3%. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich isotherm models. Pseudo first-order and pseudo second-order kinetic models were used to test the adsorption kinetics. The adsorption capacity and the rate of adsorption for DBT was found to be 1.54 mg/g and 0.74, respectively. Kinetic studies indicated that the sorption of DBT followed the pseudo first-order kinetic model with a correlation coefficient of 0.9912.

Degradation of anticorrosive agent benzotriazole by electron beam irradiation: Mechanisms, degradation pathway and toxicological analysis

Benzotriazole (BTA), which is extensively served as household and engineering agent, is one of the emerging and persistent contaminants. Despite the spirit to remove BTA is willing, the traditional wastewater treatments are weak. Therefore, the degradation of BTA via electron beam was systematically explored in this study. It turned out that after 5.0 kGy irradiation, even 87.5 mg L−1 BTA could be completely removed, and the irradiation conformed perfectly to the pseudo first-order kinetics model. The effects of solution pH, inorganic anions (CO32−, HCO3−, NO3−, NO2−, SO42−, SO32−, Cl−), and gas atmosphere were all explored. And results indicated that oxidative hydroxyl radicals played critical role in BTA irradiation. Additionally, presence of H2O2 and K2S2O8 promoted significantly not only degradation extent but also mineralization efficiency of BTA due to they both augmented the generation of oxidative free radicals. Moreover, by combining theoretical calculations with experimental results, it could be inferred that degradation of BTA was mainly carried out by the benzene ring-opening. Further toxicity evaluation proved that as irradiation proceeded, the toxicity alleviated. Taken together, there were various indications that BTA could be effectively eliminated by electron beam irradiation in aquatic environments.

Aging shapes Cr(VI) speciation in five different soils

To make sound decisions regarding management of heavy metal contamination in soils, it is necessary to understand contaminant transformations over extended periods. In this study, sequential extraction methods were applied to quantify the changes of Cr fractions [available Cr(VI), immobile Cr(VI) and immobile Cr(III)] in five contrasting soils spiked with Cr(VI) over a 240-day incubation. Results showed that available Cr(VI) in soils continually decreased during aging, with a sharp decline occurring in the first 30 days. The best fit of available Cr(VI) data was obtained using an Elovich model for Brunisol and Anthrosol-1, a fractional power model for Anthrosol-2, and a pseudo first-order kinetic model for Luvisol-1 and Luvisol-2. After aging for 240 days, immobile Cr(VI) increased by 4.5–31% and immobile Cr(III) increased by 68–95% of total spiked Cr(VI) in Brunisol, Anthrosol-1 and Anthrosol-2. The two Luvisol soils had relatively high reduction rates with no Cr(VI) immobilized. A multireaction model was developed in MATLAB Simulink toolbox to describe transformation flow rates among soluble Cr(VI), adsorbed Cr(VI), immobilized Cr(VI) and immobilized Cr(III) in soils with aging. We conclude that (i) Cr(VI) reduction and immobilization were occurring concurrently in soils and competing for available Cr(VI) species; (ii) Cr(VI) reduction is favored by low soil pH and high organic carbon, while Cr(VI) immobilization occurs with cations (such as Ca2+) and Fe oxides.

Microporous activated carbon as adsorbent for the removal of noxious anthraquinone acid dyes: Role of adsorbate functionalization

Adsorption phenomenon is affected by the nature and the presence of different functional groups on the adsorbates. Present study focuses on the influence of the groups (–CH3 and –NHCOCH3) linked to the model pollutants i.e. anthraquinone acid dyes such as acid blue 25 (AB 25), acid blue 40 (AB 40) and acid blue 129 (AB 129) in adsorption process. For this adsorptive study, a microporous activated carbon developed from demineralised kraft lignin (DKL) in an oxidizing atmosphere (surface area 1305 m2g−1; micropore volume 0.374 cm3g−1) was utilized as adsorbent and surprisingly a small but visible difference was observed in the experimental adsorption values of the chosen dyes. The dyes followed an adsorption order: AB 25 < AB 40 < AB 129 with experimental values 0.501, 0.561 and 0.601 mmolg−1 for AB 25, AB 40 and AB 129, respectively. Results indicated that the methyl groups attached to the AB 129 dye cause an increase in the hydrophobicity which further enhances its adsorption as compared to other acid dyes, whereas, hydrophillicity as well as tautomerism is responsible for the adsorptive removal of AB 40 onto the developed adsorbent. Since AB 25 doesn’t have any side group at phenyl ring, therefore, shows minimum removal efficiency. Furthermore, the effect of temperature was also investigated and the adsorption of dyes on activated carbon increase from 0.501 to 0.547, 0.561–0.610 and 0.601–0.665 mmolg−1, for AB 25, AB 40 and AB 129, respectively on increasing the temperature from 25° to 45°C. The small positive values of enthalpy change (ΔH°) obtained, reveals the physiosorptive nature of adsorption and confirms its endothermic nature. The adsorption isotherm data was examined by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models and the isotherm data fitted well to the Langmuir model. The kinetic study showed that the adsorption equilibrium was attained in 240 min for each dye. Pseudo-first order, Pseudo-second order and Elovich kinetic models were applied and Pseudo-second order model followed the adsorption kinetic process. The results of this study will pave the way to utilize carbons from wastes for the noxious acid dyes removal. Moreover, the work carried out could open an ample space for utilising porous carbons for treatment of the wastewater/sea water containing dyes.

Adsorptive Studies for the Removal of Crystal Violet Dye from Aqueous Solution by Using Cicca Acida L. Stem - Activated Carbon

Textile industries discharge wastewater containing various dyes including Crystal Violet dye. These dyes are very harmful for human beings, animals and plants. Therefore, the attempt is made for adsorption framework on elimination of crystal violet dye by using Cicca acida L. stem-activated carbon from aqueous solution carried out under various experimental methods and optimization conditions. Adsorption data modeled with Freundlich, Langmuir and Tempkin adsorption isotherms. Thermodynamic factors like as ∆Ho, ∆So and ∆Go were calculated, which indicated that the adsorption was spontaneous and endothermic nature. Based on kinetic study, pseudo-second order kinetic model was fit compared to the pseudo-first order kinetic model. The adsorbent has been characterized by SEM before and after adsorption of crystal violet dye solution.

Degradation of Tryptophan by UV Irradiation: Influencing Parameters and Mechanisms

The chlorination of dissolved amino acids can generate disinfection by-products (DBPs). To prevent the formation of DBPs, we examined the UV-induced degradation of tryptophan (Trp). In order to further understand the impact of UV disinfection on Trp, the effects of initial concentrations of Trp, pH, temperature, concentrations of NO3−, HCO3− and Cl− on Trp removal were investigated, and a degradation mechanism was also proposed. The results demonstrated that degradation fitted a pseudo first-order reaction kinetic model. The degradation of Trp was mainly caused by direct UV degradation. The apparent rate constant kobs decreased with the increase in initial Trp concentration and increased with increases in pH and temperature. The thermal degradation activation energy was 19.65 kJ/mol. Anions in water also had a significant influence on the degradation of Trp. HCO3− and NO3− contributed to the kobs of Trp, but Cl− inhibited the degradation rate. By electron paramagnetic resonance (EPR) spectroscopy, ·OH was proven to be formed during the degradation of Trp by UV. Based on the intermediate products of C11H15NO3, C10H15N and C9H13N detected by LC-MS-MS, the degradation pathway of Trp was speculated.

Comparative study on adsorption of cationic and anionic dyes by nanomagnetite supported on biochar derived from Eichhornia crassipes and Phragmites australis stems

Nanomagnetite supported on biochar derived from Eichhornia crassipes (MECB) and Phragmites australis (MPAB) stems were successfully synthesized by simultaneous carbonization, magnetization, and activation processes. The as-synthesized adsorbents were characterized and tested for their adsorption ability toward methylene blue (MB) and reactive blue 19 (RB 19). The results indicated that MECB was more effective than MPAB in terms of higher adsorption capacity of 88.89 mg/g for MB and 72.56 mg/g for RB 19 compared to 44.78 mg/g and 39.36 mg/g of MPAB, respectively. The adsorption of MB onto MECB and MPAB was best described by the pseudo-second-order kinetic and Langmuir isotherm models. In contrast, the pseudo-first order kinetic and Freundlich isotherm models were the most suitable models for describing the adsorption of RB 19. The thermodynamic analysis confirmed that the adsorption of the dyes onto the produced adsorbents was spontaneous and endothermic. The adsorption mechanism was identified to be related to electrostatic interaction, ion exchange, π–π stacking interaction, n–π interaction, hydrogen bonding, and pore-filling. The recycling and leaching studies proved that the prepared adsorbents exhibited high reusability and stability. This work showed that MECB and MPAB could serve as promising reusable adsorbents in removing dyes from aqueous solutions.

Synergistic effect of PMS activation by Fe0@Fe3O4 anchored on N, S, O co-doped carbon composite for degradation of sulfamethoxazole

High efficient activator is highly desired in the field of persulfate-based advanced oxidation process. In comparison with the previous studies, this study adopted nitrogen, sulfur and oxygen co-doped carbon material to support Fe0 encapsulate in Fe3O4 to prepare iron-based modified carbon composite (Fe0@Fe3O4-MC) by a facile two-step pyrolysis. Fe0@Fe3O4-MC was then used for degradation of sulfamethoxazole. The results showed that Fe0@Fe3O4-MC had superior catalytic activity for PMS activation due to the synergistic effect of iron-based compound and modified carbon. In the presence of 0.1 g/L of Fe0@Fe3O4-MC, SMX (0.04 mM) could be completely degraded within 120 min at pH 3.4 and 3 mM of PMS. The SMX degradation followed pseudo first-order kinetic model, with the rate constant of 0.12 min−1, and the mineralization of SMX achieved 48.4%. Sulfate radicals dominated in the SMX degradation. In addition to Fe0 and Fe3O4, carbon defects, graphitic N, sulfur and FeN4 also contributed to PMS activation. Fe0 oxidation was the rate-limiting step for PMS activation. Dissolved oxygen made a minor contribution to Fe0 oxidation. The intermediate products of SMX degradation were identified, and two pathways of SMX degradation were proposed. The influencing factors on SMX degradation were studied, including pH, temperature, PMS concentration, Fe0@Fe3O4-MC dosage, chloridion, carbonate and humic acids, and the influencing mechanism was discussed. This study could provide an efficient PMS activator for the degradation of emerging organic pollutants in water and wastewater.

Comparative study between activated carbon and biochar for phenol removal from aqueous solution

Removal of phenol from wastewater using local biochar (BC) was investigated, while using activated carbon (AC) as a reference material. The main parameters affecting the sorption process were initial concentration, contact time, pH, and temperature. Statistical analysis of the results showed that the maximum removal percent when using AC and BC were 95% and 55%, respectively. Experimental data showed that the removal of phenol has fast kinetics and reached equilibrium within 5 minutes. The Langmuir and Freundlich isotherm models were applied to fit the adsorption experimental data. Pseudo-first order and pseudo-second order kinetic models were employed.

Preparation of clinoptilolite/starch/CoFe2O4 magnetic nanocomposite powder and its elimination properties for cationic dyes from water and wastewater

A new magnetic nanocomposite clinoptilolite (CLT)/Starch/CoFe2O4 was synthesized using co-precipitation method. The prepared magnetic composite powder was utilized for decontamination of methylene blue dye (MBD), methyl violet dye (MVD), and crystal violet dye (CVD) from water media. The BET analysis showed that CLT modification using starch and CoFe2O4 nanoparticles improved its specific surface and the amount of specific surface area for CLT, CoFe2O4, and CLT/Starch/CoFe2O4 powder was reported to be 18.82 m2.g−1, 151.4 m2.g-1, and 104.75 m2.g−1, respectively. Experimental results showed that pH 9 had a vital role in the adsorption process of all three types. Langmuir and Redlich-Petersen isotherm models were well fitted with experimental data. Also, the maximum adsorption capacity of CVD, MBD, and MVD to the desired composite was determined as 32.84 mg.g−1, 31.81 mg.g−1, and 31.15 mg.g−1, respectively. In addition, the kinetic data of the removal process followed a pseudo-first order (PFO) kinetic model. Negative thermodynamic parameters were indicated that the process is spontaneous and exothermic. Finally, ad(de)sorption experiments' results showed that the synthesized nanocomposite adsorbent has an excellent ability to adsorb cationic dyes after several consecutive cycles.

Optimal removal of diclofenac and amoxicillin by activated carbon prepared from coconut shell through response surface methodology

Agricultural residues like coconut shell are widely available in Benin Republic and can be used as adsorbent. In this study, we determine the limits of pharmaceutical substances adsorption by activated carbon from coconut shells. The synthesis of this adsorbent was optimized by the Response Surface Methodology (RSM) with two factors: the impregnation ratio IR and activation temperature. The iodine value was considered as the performance (response) parameter of this synthesis. After characterizing the prepared activated carbon, adsorption tests were performed on diclofenac sodium (DCF) and amoxicillin (AMX) by varying the contact time and the adsorbate-adsorbent ratio Rads. The synthesis results showed that the optimal physicochemical properties of the activated carbon were observed at 740 °C with phosphoric acid (IR = 1.66). Under these optimal conditions, the activated carbon from the coconut shells presented a large microporous specific surface (SBET = 437 m2/g and Vmicro = 0.21 cm3/g), optimal iodine adsorption (930.28 mg/g), amorphous and low heterogeneous chemical composition. In addition, the prepared activated carbon was an excellent adsorbent for the removal of the pharmaceutical substances studied. The experimental adsorption data followed the Langmuir isotherm and the pseudo first-order kinetic model. However, the efficiency varied depending on the nature of the adsorbate and the adsorbate-adsorbent ratio was the main limiting factor in the adsorption process. Optimal elimination greater than 98% was noticed with Rads = 0.10 and a contact time of 15 min (90 min) for DCF (AMX). However, we noticed the complete elimination of AMX (DCF) for Rads ≤ 0.075 (Rads ≤ 0.040). It was observed that the removal efficiency of pollutant was not defined by the adsorption rate constant but the reactivity with the adsorbent.

Green Synthesis of copper Nanoparticles: Synthesis, Characterization and their application: About Future

In the present study copper oxide nanoparticles (CuNPs) were synthesized via simple and eco-friendly green route using black tea extract . Characterization of synthesized nanoparticles (NPs) was undertaken. The characteristic absorption peak of CuNPs was in range (352-355) nm in UV–Vis spectrum. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed the morphological and structural character of green NPs. The particle size was 25-50 nm. Energy dispersive spectroscopy (EDX) showed high intense metallic peak of copper (Cu), oxygen (O), carbon (C) and low intense peaks of phosphorus (P) , calcium (Ca) , sulfur (S), potassium (K) elements due to the capping action of biomolecules of plant extract in CuNPs formation. The X-ray diffraction (XRD) pattern showed distinctive peaks corresponding to (200), (220) and (311) planes revealing the high crystalline nature of synthesized CuNPs . The dyeing behavior of green CuNPs treated fabric with Acid Black 172 (AB 172) has been studied and the build up of dye, measured as exhaustion percentage (E%). Dye adsorption rate constants according to pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models were calculated. Moreover, the dye adsorption equilibrium data were fitted well to the Freundlich isotherm rather than Langmuir isotherm. The overall adsorption process follow pseudo-second order kinetics, Intraparticle diffusion and Elovich model. The CuNPs treatment produces a nylon fabric with advanced color fastness and antibacterial properties enabling them to improve human health care and reducing temperature, the environmental impacts, fabric damage, amount of dyestuff used and saving energy of conventional dyeing of nylon fabrics. This review focuses on green synthesis of CuNPs using environmentally benign reagents in minimal time paves the way for future studies on CuNPs toxicity without risking interference from potentially toxic reagents and capping agents. The use of this technique to treat nylon fabric may lead to new coloration technique and other functional improvement.

Removal of a mixture of veterinary medicinal products by adsorption onto a Scenedesmus almeriensis microalgae-bacteria consortium

The adsorption of the veterinary medicinal products (VMP) tetracycline (TET), ciprofloxacin (CIP), sulfadiazine (SDZ) and sulfamethoxazole (SMX) onto a dried Scenedesmus almeriensis microalgae-bacteria consortium was studied at several equilibrium concentrations (20 to 1000 μg/L). Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analysis were performed to investigate the surface morphology of the microalgae and to identify the effect of the antibiotics´ functional groups on the surface of the consortium of S. almeriensis and bacteria. Ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was used to determine the feasibility of this consortium for the removal of antibiotics via biosorption. Freundlich and Langmuir adsorption models were used for the mathematical description of the adsorption equilibrium. Pseudo-first order and pseudo-second order kinetic models were applied to fit the biosorption experimental data. Relative antibiotic removal was higher at low equilibrium concentrations. In the range of the initial VMP concentration studied, ciprofloxacin and tetracycline exhibited the highest removal efficiency of 43–100% and 75–82%, respectively. Likewise, ciprofloxacin and tetraciclyne presented the highest adsorption rates of 0.11–26.66 and 1.78–27.09 mg·μg−1·h−1, respectively. This study revealed that the S. almeriensis-bacteria consortium has a high biosorption power and proved that biosorption is an important mechanism in the removal of ciprofloxacin and tetraciclyne using a microalgae-based water treatment process. However, sulfadiazine and sulfamethoxazole removals did not exceed 32%.

Use of activated carbons for detoxification of a lignocellulosic hydrolysate: Statistical optimisation

In order to improve bioethanol production from hydrolysates from olive tree pruning residues the present study assessed a detoxification method using the same waste material. The objective was to develop optimal removal without diminishing fermentable sugars. A statistical optimisation study was performed for the production of activated carbons using the same olive tree pruning residue as raw material. The effect of the impregnation ratio, activation temperature and the time needed for maximum removal of the phenolic compounds was assayed. The conditions for maximum adsorption were as follows: 799.18 °C, IR 4.88 and 101.38 min of activation, removing 55%, 64% and 41% of total phenolic compounds, HMF and furfural, respectively. The activated carbon obtained under optimum conditions (Aop) was submitted to adsorption kinetics and equilibrium assays. Experimental kinetic data were well represented by a pseudo-first order kinetic and intraparticle diffusion model, which helped explain the adsorption mechanism. Experimental isotherms were analysed with Langmuir, Freundlich and Temkin models, and Langmuir best fitted the experimental data. Hydrolysate from olive tree pruning residues, detoxified with the optimum activated carbon, was fermented with a commercial Saccharomyces cerevisiae yeast, obtaining a 100% theoretical maximum ethanol yield and a 56% bioconversion of fermentable sugars.

Photocatalytic degradation of Novacron blue and Novacron yellow textile dyes by the TiO2/palygorskite nanocomposite.

The photocatalytic discoloration of industrial dyes, Novacron blue (NB) and Novacron yellow (NY), was investigated using composites based on TiO2 and natural palygorskite (Pal-Ti10 and Pal-Ti30). The method consisted of synthesizing the composites starting from a physical mixture of TiO2 and natural palygorskite in the presence of alcohol, for impregnation through calcination under conditions of temperature equal to 450 °C and atmospheric air. The characterization techniques used in this work were FTIR, XRD, XRF, SEM, particle size analysis and zeta potential. The photocatalysis for the NB dye was investigated through the application of a factorial 24 experimental design, aiming at the best experimental conditions and finally applying them in another NY industrial dye. The investigated concentrations of NB were 10 ppm and 30 ppm, the composites were synthesized using 10 and 30% (p/p) of titanium dioxide in palygorskite, the two pH values were 2.0 and 6.0 and the light intensities 9 and 18 W were used. Tests performed at pH 2.0, Pal-Ti30 composite, power 18 W and 10 ppm of dye showed 100% color removal of both dyes in 90 min. The bleaching process followed the pseudo-first order kinetic model, and the apparent constants (Kapp) were 0.0216 min-1 and 0.0193 min-1 for NB and NY dyes, respectively. The results of total organic carbon (TOC) showed mineralization of 61.70% and 58.06% for NB and NY, respectively, in 90 min of treatment, and the by-products were detected by GC-MS.

Novel CuO/Mn3O4/ZnO nanocomposite with superior photocatalytic activity for removal of Rabeprazole from water

In this work, a nanohybrid of CuO/Mn3O4/ZnO was generated through a simple hydrothermal based procedure. The CuO/Mn3O4/ZnO nanohybrid has been characterized using X-ray diffraction, transmission electron microscopy high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. UV–visible spectrophotometry and photoluminescence techniques allowed evaluation of optical properties that additionally suggested the prevalence of strong interfacial interaction between the three moieties of the nanohybrid and suppressed electron–hole recombination. The hybrid photocatalyst brought on ~ 97.02 ± 1.15% disintegration of rabeprazole when illuminated with visible light. The progress of the photodegradation was in conformity with pseudo-first order kinetic model and had a velocity constant of 0.07773 min−1. Additionally, ~ 84.45% of total organic carbon removal was achieved while chemical oxygen demand was reduced by ~ 73.01%. Using high resolution liquid chromatograph mass spectrometry technique, identification of the degraded products was made and accordingly the mechanistic route of the aforesaid degradation was proposed.

Investigation of Seeds and Peels of Citrullus colocynthis as Efficient Natural Adsorbent for Methylene Blue Dye

Natural adsorbents as low-cost materials have been proved efficient for water remediation and have significant capacity for the removal of certain chemicals from wastewater. The present investigation aimed to use Citrullus colocynthis seeds (CCSs) and peels (CCPs) as an efficient natural adsorbent for methylene blue (MB) dye in an aqueous solution. The examined biosorbents were characterized using surface area analyzer (BET), scanning electron microscope (SEM), thermogravimetric analyzer (TGA) and Fourier transform infra-red (FT-IR) spectroscopy. Batch adsorption experiments were conducted to optimize the main factors influencing the biosorption process. The equilibrium data for the adsorption of MB by CCSs were best described by the Langmuir isotherm followed by the Freundlich adsorption isotherms, while the equilibrium data for MB adsorption by CCPs were well fitted by the Langmuir isotherm followed by the Temkin isotherm. Under optimum conditions, the maximum biosorption capacity and removal efficiency were 18.832 mg g−1 and 98.00% for MB-CCSs and 4.480 mg g−1 and 91.43% for MB-CCPs. Kinetic studies revealed that MB adsorption onto CCSs obeys pseudo-first order kinetic model (K1 = 0.0274 min−1), while MB adsorption onto CCPs follows the pseudo-second order kinetic model (K2 = 0.0177 g mg−1 min−1). Thermodynamic studies revealed that the MB biosorption by CCSs was endothermic and a spontaneous process in nature associated with a rise in randomness, but the MB adsorption by CCPs was exothermic and a spontaneous process only at room temperature with a decline in disorder. Based on the obtained results, CCSs and CCPSs can be utilized as efficient, natural biosorbents, and CCSs is promising since it showed the highest removal percentage and adsorption capacity of MB dye.

Ultrasound assisted Fenton-like degradation of dyes using copper doped graphitic carbon nitride.

A novel copper doped graphitic carbon nitride (Cu-C3N4) was successfully synthesized and used as an effective Fenton-like catalyst. Cu-C3N4 was characterized by scanning electron microscopy, surface area analyzer, Fourier transform infrared spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy. Effect of process parameters including catalyst dosage, hydrogen peroxide (H2O2) concentration, solution pH, and initial methylene blue (MB) concentration was investigated to evaluate catalytic performance. The pseudo first-order kinetic model was used to describe the catalytic process. The enhancement of MB degradation is observed assisted by ultrasound. MB degradation of 96% is obtained within 30 min in Cu-C3N4/H2O2/ultrasound system, and the corresponding rate constant is 0.099 min-1. Effective MB degradation is obtained over a broad pH range (3.3-9.9). The catalytic mechanism is examined by ultraviolet-visible spectra, quenching test, and electron spin resonance determination. The dominant mechanism of MB degradation is ascribed to the ultrasonic H2O2 activation by Cu-C3N4 for hydroxyl radical generation. Cu-C3N4 has good reusability and is effective to degrade rhodamine B and acid orange 7. This work not only contributes to the field of wastewater treatment, but also provides insights into the synthesis of Fenton-like catalysts. The results manifest that Cu-C3N4 is a promising Fenton-like catalyst for dye degradation in the field of environmental pollution remediation.

Removal of Zn(II) and Ni(II) heavy metal ions by new alginic acid-ester derivatives materials

The present work concerns the preparation of new materials based on alginic acid (AA) and diols in a facile and efficient process by improving the adsorption properties of Zn(II) and Ni(II) metal ions on the modified AA. The materials were analysed by zeta potential, thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), in addition to the Fourier Transform InfraRed spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) before and after the adsorption behaviour was conducted. The results show that the esterification of AA with diols of different lengths significantly improves its adsorption efficiency of Zn(II) and Ni(II) with Qmax up to 200 mg/g and 185.185 mg/g respectively. Equilibrium and kinetic studies showed that the Langmuir and Freundlich adsorption isotherm models fit the experimental data well, and followed a pseudo-first order kinetic model and the particle diffusion model with correlation coefficients R2 ≈ 1.

Sequestration of toxic Pb(II) ions using ultrasonic modified agro waste: Adsorption mechanism and modelling study

Treating the effluents from industries by using biological and agricultural wastes is an emerging field of research. In this study, three different biosorbents are prepared from tamarind seeds such as; raw, sulphuric acid-modified and ultrasonic-assisted surface-modified tamarind seed powder has been utilized to expel the Pb (II) ions from synthetic solution. The surface characteristics of the newly synthesized raw and surface modified agro-waste biomass were studied by FTIR and SEM. An experimental study was carried out to investigate the effect of different parameters on adsorption of Pb(II) ions using raw, sulphuric acid-modified and ultrasonic-assisted surface-modified tamarind seeds. The maximum Pb(II) ions adsorption was found at pH - 6.0, temperature - 303 K, biosorbent dosage - 3.5 g/L and contact time - 60 min for raw tamarind seeds and 30 min for sulphuric acid-modified and ultrasonic-assisted surface-modified tamarind seeds. The adsorption mechanism was described by Langmuir isotherm and pseudo-first order kinetic model. Among the three biosorbents, ultrasonic-assisted surface-modified tamarind seeds show higher adsorption capacity (18.86 mg/g) of Pb(II) ions removal from the synthetic solution. The thermodynamic study declared that the present Pb(II) ions adsorption onto the prepared biosorbents was spontaneous, exothermic and followed physical adsorption process. Results have shown that tamarind seed was found to be the best adsorbent in the expulsion of Pb(II) ions from the wastewater environment.