Organic wastewater causes serious environmental pollution, and catalytic oxidation is promising technique for wastewater treatment. Developing green and effective catalysts is currently challenging. In this work, green synthesis of nano zerovalent iron loaded onto porous biochar derived from popcorn is conducted, and catalytic oxidation of Rhodamine B (RhB) is evaluated in the presence of H2O2. Effect of process factors is examined on catalytic performance for RhB removal. The mechanism of RhB removal is discussed by characterizations (Fourier transform infrared spectra and Raman) and UV–vis spectra. RhB removal is improved with high catalyst dosage, low initial RhB concentration, and high reaction temperature, while it is slightly influenced by carbonization temperature of biochar, H2O2 dosage and pH value. Under conditions of BC-250 1.0 g/L, H2O2 0.01 mol/L, pH 6.1, and temperature 30 °C, the removal rate of RhB is 92.27% at 50 min. Pseudo first-order kinetics is used to fitting experimental data, and the activation energy for RhB removal in BC-250/H2O2 system is 39 kJ/mol. RhB removal in BC-250/H2O2 system can be attributed to adsorption effect and catalytic oxidation with the dominant role of hydroxyl radical. This work gives insights into catalytic oxidation of organic wastewater using green catalyst.

To solve the problem of water pollution, researchers have proposed a photocatalytic degradation technology, in which the key factor is the development of efficient photocatalytic materials. Graphitic carbon nitride (g-C3N4), an n-type semiconductor, has been widely studied due to its suitable band gap (2.7 eV), low cost, easy preparation, non-toxicity, and high photostability. However, the pure-phase g-C3N4 still has defects such as low specific surface area, insufficient visible light absorption, low charge mobility, few active sites for interfacial reaction, and easy recombination of photogenerated electron–hole pairs, which leads to the lower photocatalytic activity of g-C3N4. Aiming at the problems mentioned above, this paper focus on the synthesis of g-C3N4-based composites with high photocatalytic activity via lemon juice induction method. Thiourea and lemon juice were selected as precursors, and carbon quantum dots (CQDs) as electron mediators were introduced anchoring on the surface of g-C3N4 to build g-C3N4/CQDs with compact interface. The results showed that small-sized CQDs are uniformly distributed on the surface of g-C3N4, and the g-C3N4/CQDs composite has a 2D0D structure, which reduces the recombination of photogenerated electron–hole pairs. The photocatalytic degradation efficiency of 4% g-C3N4/CQDs for RhB reaches the highest data of 90.9%, and the photocatalytic degradation rate is 0.016 min− 1, which is about 2.3 times that of g-C3N4. After four cycles of photocatalytic reaction, the photocatalytic degradation efficiency of the material remained at 81.7%. Therefore, the g-C3N4/CQDs synthesized via lemon juice induction has a more stable microstructure, and the charge separation efficiency is greatly improved, which is suitable for practical photocatalytic environmental protection.

In this paper, AgCl/Ag3PO4/diatomite photocatalyst is successfully synthesized by microemulsion method and anion in situ substitution method. X-ray diffraction (XRD), photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) are used to study the structural and physicochemical characteristics of the AgCl/Ag3PO4/diatomite composite. Using rhodamine B (RhB) as a simulated pollutant, the photocatalytic activity and stability of the AgCl/Ag3PO4/diatomite composite under visible light are evaluated. In the AgCl/Ag3PO4/diatomite visible light system, RhB is nearly 100 % degraded within 15 minutes. And, after five cycles of operation, the photocatalytic activity of AgCl/Ag3PO4/diatomite remains at 95 % of the original level, much higher than that of pure Ag3PO4 (40 %). In addition, the mechanism of enhanced catalytic performance is discussed. The high photocatalytic performance of AgCl/Ag3PO4/diatomite composites can be attributed to the synergistic effect of Ag3PO4, diatomite and AgCl nanoparticles. Free radical trapping experiments are used to show that holes and oxygen are the main active species. This material can quickly react with dye molecules adsorbed on the surface of diatomite to degrade RhB dye to CO2 and H2O. Even more remarkably, AgCl/Ag3PO4/diatomite can maintain above 95 % photo-degradation activity after five cycles.

In this work, a carbon-doped carbon nitride photocatalyst is successfully synthesized through a simple centrifugal spinning method after heat treatment. The morphology and properties of the prepared photo catalyst are characterized by Xray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectrophotometer (UV-vis), and specific surface area. The results show that the band gap of the prepared sample, g-CN-10 is 2.1 eV, is significantly lower than that of pure carbon nitride, 2.7 eV. As the amount of cotton candy increased, the absorption capacity of the prepared catalyst for visible light is significantly enhanced. In addition, the degradation efficiency of Rhodamine B (RhB) by sample g-CN-10 is 98.8 % over 2h, which is twice that value of pure carbon nitride. The enhancement of photocatalytic ability is attributed to the increase of specific surface area after the carbon doping modifies carbon nitride. A possible photocatalytic degradation mechanism of carbon-doped carbon nitride is also suggested.

Cubic mesocrystal CeO2 was synthesized via a hydrothermal method with glutamic acid (C5H9NO4) as a template. The XRD pattern of a calcined sample shows the face-centered cubic fluorite structure of ceria. Transmission electron microscopy (TEM) and the selected-area electron diffraction (SAED) pattern revealed that the submicron cubic mesocrystals were composed of many small crystals attached to each other with the same orientation. The UV-visible adsorption spectrum exhibited the red-shift phenomenon of mesocrystal CeO2 compared to commercial CeO2 particles; thus, the prepared materials show tremendous potential to degrade organic dyes under visible light illumination . With a concentration of a rhodamine B solution of 20 mg/L and a catalyst amount of 0.1 g/L, the reaction showed higher photocatalytic performance following irradiation with a xenon lamp (≥ 380 nm). The decoloring rate can exceed 100% after 300 min.

In the present work, WO3 and WO3-TiO2 were prepared by the chemical deposition method. Structural variations, surface state and elemental compositions were investigated for preparation of WO3-TiO2 sonocatalyst. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) were employed for characterization of these new photocatalysts. A rhodamine B (Rh.B) solution under ultrasonic irradiation was used to determine the catalytic activity. Excellent catalytic degradation of an Rh.B solution was observed using the WO3-TiO2 composites under ultrasonic irradiation. Sonocatalytic degradation is a novel technology of treating wastewater. During the ultrasonic treatment of aqueous solutions sonoluminescence, cavitaties and "hot spot" occurred, leading to the dissociation of water molecules. In case of a WO3 coupled system, a semiconductor coupled with two components has a beneficial role in improving charge separation and enhancing TiO2 response to ultrasonic radiations. In case of the addition of WO3 as new matter, the excited electrons from the WO3 particles are quickly transferred to TiO2 particle, as the conduction band of WO3 is 0.74 eV which is -0.5 eV more than that of TiO2. This transfer of charge should enhance the oxidation of the adsorbed organic substrate. The result shows that the photocatalytic performance of TiO2 nanoparticles was improved by loading WO3.

A nanocomposite consisting of Fe3O4 and MWCNT was produced via sol-gel technique using FeCl3 along with MWCNT by calcination at 300℃. The degradation effect of rhodamine B dye has been investigated under UV illumination in a darkroom. The degradation reaction was studied by monitoring the discoloration of dye as a function of irradiation time using UV-visible spectrophotometeric technique. The Fe3O4-MWCNT samples have continuous degradation ability under the UV illumination with the first order kinetics and the dye removal was better than in the pristine Fe3O4. The resultant composite catalyst was found to be efficient for the photo-Fenton reaction of the dye.

A colorimetric chemosensors Sn2+ have been designed and synthesized by three steps. The spirolactam ring-opening process of rhodamine B is one of the most useful mechanisms for controlling fluorescence properties. Herein, new fluorescent chemosensors 1 and 2 based on rhodamine B containing phenothiazine derivertive were synthesized. They exhibit selective fluorescence enhancement behaviour in the presence of Sn2+ ion. Complexation between these compounds and the metal cations were confirmed through continuous variation method. It is observed that compounds 1, 2, and Sn2+ ion are complexed by 1:1 formation. Especially the proposed compounds 1 and 2 exhibit quick, simple and facile synthetic route.

This study elucidates the COD removal of dye (Rhodamine B) through electrochemical reaction. Effects of current density (7.2 to 43.3 mA/cm2), electrolyte type (NaCl, KCl, Na2SO4, HCl), electrolyte concentration (0.5 to 2.0 g/L), air flow rate (0 to 4 L/min) and pH (3 to 11) on the COD removal of Rhodamine B were investigated. The observed results showed that the increase of pH decrease the COD removal efficiency. Whereas, the increase of current density, NaCl concentration and air flow rate caused the increase of the COD removal of Rhodamine B.

The purpose of this study is to degradation of Rhodamine B (RhB, dye) and N, N-Dimethyl-4-nitrosoaniline (RNO, indicator of the electro-generation of OH radical) in solution using boron doped diamond (BDD) electrode. The effects of applied current (0.2~1.0 A), electrolyte type (NaCl, KCl, and Na2SO4) and electrolyte concentration (0.5~3.0 g/L), solution pH (3~11) and air flow rate (0~4 L/min) were evaluated. Experimental results showed that RhB and RNO removal tendencies appeared with the almost similar thing, except of current. Optimum current for RhB degradation was 0.6 A, however, RNO degradations was increased with increase of applied current. The RhB and RNO degradation of Cl type electrolyte were higher than that of the sulfate type. The RhB and RNO degradation were increased with increase of NaCl concentration and optimum NaCl dosage was 2.5 g/L. The RhB and RNO concentrations were not influenced by pH under pH 7. Optimum air flow rate for the oxidants generation and RhB and RNO degradation were 2 L/min. Initial removal rate of electrolysis process was expressed Langmuir - Hinshelwood equation, which is used to express the initial removal rate of UV/TiO2 process.

This study has carried out to evaluate the effect of NaCl as electrolyte of single (electrolysis and UV process) and complex (electrolysis/UV) processes for the purpose of removal and mineralization of Rhodamine B (RhB) dye in water. It also evaluated the synergetic effect on the combination of electrolysis and UV process. The experimental results showed that RhB removal of UV process was decreased with increase of NaCl, while RhB removal of electrolysis and electrolysis/UV process was increased with increase of NaCl. The decolorization rate of the RhB solution in every process was more rapid than the mineralization rate identified by COD removal. The latter took longer time for further oxidation. Absorption spectra of an aqueous solution containing RhB showed a continued diminution of the RhB concentration in the bulk solution: concomitantly, no new absorption peaks appeared. This confirmed the decolorization of RhB, i.e., the breakup of the chromophores. It was observed that RhB removal in electrolysis/UV process is similar to the sum of the UV and electrolysis. However, it was found that the COD of RhB could be degraded more efficiently by the electrolysis/UV process than the sum of the two individual process. A synergetic effect was demonstrated in electrolysis/UV process.

The feasibility study of the application of the photoelectrocatalytic and electrolytic/UV decolorization of Rhodamine B (RhB) was investigated in the photoelectrocatalytic and electrolytic/UV process with TiO₂ photoelectrode and DSA (dimensionally stable anode) electrode. Three types of TiO₂ photoelectrode were used. Thermal oxidation electrode (Th-TiO₂) was made by oxidation of titanium metal sheet; sol-gel electrode (SG-TiO₂) and powder electrode (P-TiO₂) were made by coating and then heating a layer of titania sol-gel and slurry TiO₂ on titanium sheet. DSA electrodes were Ti and Ru/Ti electrode. The relative performance for RhB decolorization of each of the photoelectrodes and DSA electrodes is: Ru/Ti > Ti > SG-TiO₂ > Th-TiO₂. It was observed that photoelectrocatalytic decolorization of RhB is similar to the sum of the photocatalytic and electrolytic decolorization. Therefore the synergetic effect was not showed in pthotoelectrocatalytic reaction. Na₂SO₄ and NaCl showed different decolirization effect between pthotoelectrocatalytic and electrolytic/UV reaction. In the presence of the NaCl, RhB decolorization of Ru/Ti DSA electrode was higher than that of the other photoelectrode and Ti electrode. Optimum current, NaCl dosage and UV lamp power of the electrolytic/UV process (using Ru/Ti electrode) were 0.75 A, 0.5 g/L and 16 W, respectively.

For the RhB removal from the wastewater, electrochemical method was adapted to this study. Three dimensionally stable anode (Pt, Ir and Ru) and graphite and Ru cathode were used. In order to identify decolorization, the effects of electrode, current density, electrolyte and air flow rate were investigated. The effects of electrode material, current, electrolyte concentration and air flow rate were investigated on the decolorization of RhB. Electro-Fenton's reaction was evaluated by added Fe2+ and H2O2 generated by the graphite cathode. Performance for RhB decolorization of the four electrode systems lay in: Ru-graphite > Ru-Ru > Ir-graphite > Pt-graphite. A complete color removal was obtained for RhB (30 mg/L) at the end of 30 min of electrolysis under optimum operations of 2 g/L NaCl concentration and 2 A current. Fe2+ addition increased initial reaction and decreased final RhB concentration. However the effect was not high.

The electro-chemical decolorization of Rhodamine B (RhB) in water has been carried out by electro Fenton-like process. The effect of distance, material and shape of electrode, NaCl concentration, current, electric power, H2O2 and pH have been studied. The results obtained that decrease of RhB concentration of Fe(+)-Fe(-) electrode system was higher than that of other electrode system. The decrease of RhB concentration was not affected electrode distance and shape. Decolorization of electro Fenton-like reaction, which was added H2O2 onto the electrolysis using electrode was higher than electrolysis. Addition of NaCl decreased the electric consumption. The lower pH is, the faster initial reaction rate and reaction termination time observed.

The photocatalytic decolorization of Rhodamine B (RhB) was studied using packed-bed reactor and immobilized TiO2/UV System. The 20 W UV-A, UV-B and UV-C lamps were employed as the light source. The effect of shape and surface polishing extent of reflector, distance between the reactor and reflector, reactor material were investigated. The results showed that the order of the initial reaction constant with reflector shape was round > polygon > W > rhombus. The optimum distance between the reactor and reflector was 2 cm. The initial reaction constant of quartz reactor was 1.46 times higher than that of the PVDF reactor.

The biosorption of dye, Rhodamine B(Rh-B), onto waste activated sludge was investigated. The biosorption capacity and contact time were shown as a simulation of dye adsorption equilibrium and kinetics models. We observed that biosorption of Rh-B occurred rapidly less than 4hr. These experimental data could be better fitted by a pseudo-second-order rate equation than a pseudo-first-order rate equation. The equilibrium dependence between biosorption capacity and initial concentration of Rh-B was estimated and it was found that the equilibrium data of biosorption were fitted by four kinds of model such as Langmuir, Freundlich, Redlich- Peterson, and Koble-Corrigan model. The average percentage errors, ε(%), observed between experimental and predicted values by above each model were 21.19%, 9.97%, 10.10% and 11.76%, respectively, indicating that Freundlich and Redlich-Peterson model could be fitted more accrately than other models.

The properties of biosorption of dye(Rhodmine B) was investigated to figure out the effects of temperature as a function of dye concentration and sludge concentration by the Langmuir and Lagergen adsorption model. It was found that the uptake capacity of biosorption was increased at low temperature. The Langmuir adsorption model was found suitable for describing the biosorption of the dye. The experimental results indicated that the dye uptake process followed the pseudo-first-order kinetics.

The photocatalytic oxidation of Rhodamine B (RhB) was studied using immobilized TiO2 and fluidized bed reactor. Immobilized TiO2 onto GF/C was employed as the photocatalyst and a 30 W germicidal lamp was used as the light source and the reactor volume was 4.8 L. The effects of parameters such as the amounts of photocatalyst, initial concentration, initial pH, air flow rate and anion additives (NO3-, SO42-, Cl-, CO32-) competing for reaction. The results showed that the optimum dosage of the immobilized TiO2 was 40.0 g/L. Initial removal rate of immobilized TiO2 was expressed Langmuir - Hinshelwood equation.