Chemical Oxygen Demand Measurements Research Articles

Biosynthesis of NiO Nanoparticles Using Soursop (Annona muricata L.) Fruit Peel Green Waste and Their Photocatalytic Performance on Crystal Violet Dye

A simple, inexpensive, and eco-friendly route has been demonstrated for synthesizing spherical NiO nanoparticles (NiO NPs) with a size range between 20 and 90 nm using aqueous extract of soursop (Annona muricata L.) fruit peel green waste which plays the role of reducing and stabilizing agent during the synthesis. The formation, morphology, structure and other physicochemical properties of the resulting NiO NPs were characterized by various experimental techniques such as X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The photocatalytic performance of the prepared NiO NPs was assessed toward the photodegradation of crystal violet (CV) dye as a model pollutant under sunlight illumination. The measurement of chemical oxygen demand (COD) values verified the degree mineralization of CV dye. The results show that nearly 99.0% of CV pollutant was photodegraded at 105 min of illumination, making it a promising candidate for wastewater treatment.

Solar light-driven CeVO4/ZnO nanoheterojunction for the mineralization of Reactive Orange 4.

In this study, we synthesized CeVO4/ZnO nanoheterojunction photocatalyst through hydrothermal-precipitation method. The prepared photocatalyst was characterized by Fourier transform infrared analysis (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) with elemental color mapping (ECM), high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED) pattern, UV-vis diffuse reflection spectroscopy (UV-vis-DRS), BET, and photoluminescence (PL) spectroscopy. The BET surface area of CeVO4/ZnO is 10.50m2/g. The photocatalytic activity of CeVO4/ZnO nanoheterojunction under solar light was investigated for the degradation of Reactive Orange 4 (RO 4). CeVO4/ZnO has been found to be more effective for mineralization of RO 4 than the prepared ZnO at neutral pH. The addition of TBA (•OH scavenger) contributes a significant decrease in the photodegradation efficiently of the catalyst. Chemical oxygen demand (COD) measurements confirmed the complete mineralization of RO 4. In addition, it found that the photocatalyst was stable and reusable. Graphical abstract.

Measurement of Aluminum and Chemical Oxygen Demand in the Effluent of Mordanted Cotton Against Environmental Regulations

Despite toxicity concerns of chemical mordants used in natural dyeing, there is limited research on the measurement, quality, and safe disposal of the chemical mordant effluent. This study measured the aluminum ions across the premordanting process of cotton print cloth using inductively coupled plasma mass spectrometry and calculated the oxidizable organic matter in the effluent through chemical oxygen demand (COD). The amount of aluminum absorbed by the cotton print cloth was low (2.31%–5.16%). The effluent COD was 23.91g COD/kg. Upon neutralization of the acidic condition, the aluminum in the effluent met discharge to freshwater regulations, and the COD met discharge to U.S. municipal sewage systems. However, the Global Harmonized System restricts aluminum acetate dibasic from organic certification due to its boric acid content. The high mordant concentration in the effluent supports the reuse of mordant baths but not direct disposal to the land or standing waters.

Reduction of chemical oxygen demand in a conventional activated sludge system treating coke oven wastewater

The best available techniques reference document for iron and steel production sets a strict limit value for the treated effluent of coke oven wastewater treatment plants regarding Chemical Oxygen Demand (COD). The objective was to find options to decrease residual COD, in order to safely meet the threshold for a specific plant. Membrane filtration experiments showed that the remaining COD can only be reduced by 6–27%, indicating that the majority of compounds are dissolved, not suspended. Inert COD measurements of the effluent showed that 82–96% of the residual COD is non-biodegradable. Of the approximately 30 different organic substances found in the influent, Gas Chromatography - Mass Spectrometry (GC-MS) analysis detected, two-thirds were also present in the biologically treated wastewater. These results proved that the activated sludge treatment step is operating at its maximum achievable efficiency, thus further polishing steps had to be investigated to achieve the required COD. A combined physico-chemical post-treatment of the biologically treated effluent showed outstanding results and managed to decrease the COD to below 220 mg/l in all tested samples. This solution could be used universally in those coke oven wastewater treatment plants that are experiencing issues with levels of residual COD in their discharge.

Photoactive CdO:TiO2 nanocomposites for dyes degradation under visible light

CdO:TiO2 nanocomposites were synthesized by sol-gel precipitating method for different volume ratios and examined the photoactivity of synthesized nanomaterials. The structure of nanomaterials was analysized by X-ray diffraction (XRD) while FE-SEM and HR-TEM were used for morphological property. XRD patterns showed anatase phase for TiO2 and cubic phases for CdO, respectively, where as a mixed structure was observed for CdO:TiO2. The optical bandgaps were found between 2.10 and 3.25 eV for the different volume ratios. The CdO:TiO2 (1:1) was found suitable for the degradation of both organic methyl blue and methyl orange dye under visible light. The boosted charge separation and low recombination rates were responsible to enhance the performance of the photocatalic activity in visible light. The photodegradation was increased from 75% to 99% for CdO to CdO:TiO2 for methyl orange dye at a pH value of 7. The mineralization property of the dyes was confirmed by biological oxygen and a chemical oxygen demand measurements.

Real-Time on-Line Photoelectrochemical Determination of Chemical Oxygen Demand By Field-Effect Transistor Using an Extended Gate with Controllable Nanostructures

Introduction Chemical oxygen demand (COD) is the oxygen equivalent on degradation of the organic compounds, which is a significant parameter of water quality assessment.[1] Currently, photoelectrochemical (PEC) COD determination method has appealed intensive attention due to its strong oxidation ability and low recombination rate of photogenerated electron-hole pairs. However, one common drawback in the conventional PEC measurements is the requirement of a three-electrode configuration which is an impediment for the device miniaturization.[2] Herein, we developed a real-time on-line PEC sensor toward sensitive and rapid COD determination based on extended-gate field-effect transistors (EGFETs). The performance of the EGFETs-based sensors can be easily modulated by alternating the sensing elements on the extended gate electrode.[3,4]Experimental sectionIn the PEC thin-layer COD detection cell, the working electrode is composed of 3D TiO2 nanotube arrays on Ti mesh (3D TNTAs/Ti) which was prepared by electrochemical anodization (Fig. 1). The 3D TNTAs/Ti working electrode was connected to the gate of MOSFET, forming an extended-gate field-effect transistor sensor. Characterization of electrodes, PEC measurements and COD determination were then conducted in details. Besides 3D TNTAs, photoelectrodes with other controllable nanostructures were also selected and the corresponding sensing performance was investigated. Results and Conclusions Using different sensing elements on the extended-gate electrode, EGFETs-based sensors have been developed to measure pH, DNA, protein, urea, glucose, etc. Here, self-assembled 3D TiO2 nanotube arrays decorated with Pt nanoparticles was firstly employed as the sensor electrode in the EGFET-based sensor toward COD detection. The COD detection conditions have been firstly optimized, and then the analytical principle has been proposed and validated.The COD sensor shows a low detection limit of 0.12 mg/L COD and a wide linear range from 1.44 mg/L to 672 mg/L at the flow rate of 1.0 mL/s, suggesting its great potential application in real-time on-line COD measurement. The validity of the proposed device has been testified in both synthetic and real water samples. The sensitive and stable detection can be attributed to synergistic effects from the superior oxidation ability of the 3D TNTAs/Ti sensing electrode, the flexibility of EGFET-based device, and the unique structure of the thin-layer reactor.In order to demonstrate the feasibility of the proposed device in practical COD determination, the actual wastewater samples were analyzed by both conventional dichromate method and the proposed sensor. The relative standard deviation (RSD) obtained from the proposed sensor were below 9% indicating that the reproducibility is good. The COD values determined by the proposed sensor show excellent correspondence with the conventional dichromate method according to the small relative error within 10%. Moreover, other EGFET-based sensors with various controllable nanostructures were also investigated, and the underlying mechanism was verified.

Synchronous role of coupled adsorption-photocatalytic degradation of Direct Red 80 with nanocrystalline TiO2-coated non-woven fibres materials in a static batch photoreactor

The aim of this research is the application of the industrially produced TiO2-coated non-woven fibres for coupled adsorption-photocatalytic degradation of synthetic textile dye Direct Red 80. The adsorption efficiency of DR80 samples has been studied in the dark. The tested TiO2 catalyst, that exhibited significant adsorption capacities due to its high specific surface area, proven to be effective photocatalyst for photodegradation of the studied dye. The effect of the experimental parameters, such as initial dye concentration, pH and temperature on the photodegradation, were investigated. The effect of inorganic ions (Na2SO4, NaCl, NaNO3, CH3COONa, NaHCO3 et Na2HPO4) was also studied. A pseudo-first-order kinetic reaction was illustrated using the Langmuir-Hinshelwood model and rate constant and adsorption equilibrium constant were calculated (k = 1.1873 mg/L.min and KLH = 0.0660 L/mg, respectively). The highest photodegradation efficiency is obtained at pH = 3. The presence of HPO42−, HCO3−, CH3COO− ions decreased the photodegradation rate, however, Cl−, NO3− increased the reaction rate. The degradation of pollutant has been monitored by spectrophotometry. To evaluate the extent of mineralization of the studied dye, Chemical Oxygen Demand (COD) measurements during the experiment were conducted, where the important abatement of 88.64% was reached after 7 h of the treatment. The identification of the reactive intermediates products by using high performance liquid chromatography (HPLC), allowed suggesting the oxidative degradation mechanism for Direct Red 80 dye.

Highly efficient degradation of concentrated Rhodamine-B effluent using environment friendly needle-plate non-thermal plasma probe

A simple, portable and cost effective design of single (1 T) and triple (3 T) needle-plate geometry of atmospheric pressure plasma probes was used to study the degradation of aqueous effluent solution made up of Rhodamine B (Rh-B). Mainly these torches were used to generate the Advanced Oxidative Species (AOS) useful for the degradation of 10−4 M aqueous solution of Rh-B dye. The optical emission spectroscopy was used to understand the nature of oxidizing species generated during the plasma formation.The de-colorization as well as degradation of dye solution (effluent) was monitored using UV–vis spectroscopy. Further, Chemical Oxygen Demand (COD) measurements were used to investigate quality of plasma treated and untreated effluent. Liquid Chromatography Mass Spectroscopy (LCMS) measurements were used to understand degradation pathway of the Rh-B effluent. In order to increase the amount of effluent to be degraded, the 1 T assembly was modified to 3 T so as to treat flowing effluent solution. The concentration of chemically active species such as OH·, O3 etc. generated in the 3 T assembly was found to be higher than that of 1 T assembly. In order to check the toxicity of the plasma treated effluent, the growth of soil microbes was investigated by feeding plasma treated effluent solution. The result indicate that, the aqueous solution of effluent kill the soil microbes whereas post plasma treated effluent (PTW/pH-PTW) boost the growth of soil microbes. Therefore, present study also depicts that plasma treated effluent is not only nontoxic but also it facilitates the growth of soil microbes.

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

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

Degradation of Reactive Red 120 dye by a heterogeneous Sono-Fenton process with goethite deposited onto silica and calcite sand

The degradation of Reactive Red 120 dye (RR-120) in synthetic waters was studied. Two processes were considered: homogeneous sono-Fenton with iron(II) sulfate and heterogeneous sono-Fenton with synthetic goethite and goethite deposited onto silica and calcite sand (modified catalysts GS and GC, respectively). In 60 min of reaction, the homogeneous sono-Fenton process allowed a degradation of 98.10 %, in contrast with 96.07 % for the heterogeneous sono-Fenton process with goethite at pH 3.0. The removal of RR-120 increased when the modified catalysts were used instead of bare goethite. Chemical oxygen demand (COD) and total organic carbon (TOC) measurements showed that the highest TOC and COD removals were achieved with the homogeneous sono-Fenton process. Biochemical oxygen demand (BOD5) measurements allowed confirmed that the highest value of BOD5/COD was achieved with a heterogeneous sono-Fenton process (0.88?0.04 with the modified catalyst GC), demonstrating that the biodegradability of the residual organic compounds was remarkably improved.

Novel Fe2V4O13/ZnO nano-heterojunction: Effective decomposition of methyl orange under solar light irradiation

A simple and efficient method was established for the synthesis of Fe2V4O13/ZnO nanocomposites. Photocatalytic degradation of Methyl Orange (MO) dye by using synthesized photocatalysts was investigated under solar irradiation. The effects of operational parameters such as pH, catalyst loading, initial dye concentration, and reusability were studied. The complete mineralization of MO was confirmed by chemical oxygen demand (COD) measurements. Moreover, the catalyst was found to be stable and reusable.

Assessing the performance of bio compost as soil media in extensive green roof

Composted green waste is a recycled material which can be produced locally, adding value to the environmental credentials of a green roof system. As the organic component of green roof growing media, composted green waste can contribute positively to the physical requirements as well as improve environmental performance. In addition it can contain nutrients for plant growth and survival. These will not typically be provided by an inert inorganic substrate and will help establish vegetation. This study is aimed to investigate the performance of bio compost as soil media in extensive green roof with respect to different composition. Runoff were tested for total suspended solids (TS), turbidity, chemical oxygen demand (COD), pH, and color measurements. The results showed that 50% of bio compost in soil media has the best performance in term of plant growth and runoff quality.

Application feasibility of chromophoric dissolved organic matter (CDOM) absorption coefficient as the substitute for chemical oxygen demand concentration in lakes and reservoirs

化学需氧量是衡量水体中有机物量及污染程度的综合性指标，也是我国《地表水环境质量标准（GB 3838—2002）》的重要评价指标.然而，由于测定过程缓慢和使用了有毒有害试剂易于形成二次污染，现行标准的高锰酸钾和重铬酸钾化学需氧量测定方法无法做到环境友好，也不能反映当前快速和实时监测的技术需求.因此，迫切需要发展操作简便、快速高效、灵敏可靠、环境友好和环保绿色的化学需氧量替代检测方法.本文首先从文献计量学视角比较我国与世界上发达国家化学需氧量研究主题论文发文量，剖析了我国发展化学需氧量替代检测方法的迫切性.基于全国大范围65个湖库706个样本有色可溶性有机物吸收系数、化学需氧量和其他水质参数同步调查数据，构建广覆盖范围的有色可溶性有机物特征波长吸收系数和化学需氧量间高精度线性关系模型，确定了地表水环境质量评价的吸收系数阈值，模型可以广泛应用于不同类型（深水、浅水、大型、中型、小型）和不同营养状态（贫、中、富营养）湖库水体有机物浓度的定量表征，具有一定普适性.通过对比有色可溶性有机物吸收系数和传统的高锰酸钾、重铬酸钾法优势和不足，明确了有色可溶性有机物吸收系数替代化学需氧量用于湖库水体开展有机物表征和污染程度评价的可行性和应用前景.;Chemical oxygen demand (COD) is a comprehensive index to measure the amount of organic matter and reflect pollution degree of organic matter in water. Meanwhile, COD is also an important assessment index of environmental quality standard for surface water (GB 3838-2002). However, due to time consuming, the use of toxic and harmful reagents in the determination process and the easiness to produce secondary pollution, the current potassium permanganate and potassium dichromate COD determination methods are not environmentally friendly and cannot reflect the current rapid and real-time technical requirements. Therefore, there is an urgent need to develop a simple, rapid and efficient, sensitive and reliable, environmentally friendly and pollution-free green alternative detection method of COD. Firstly, from the perspective of bibliometrics by comparing total publication number of COD subject in China and the developed countries in the world, this study analyzes the urgency of developing alternative methods of COD in China. Based on the dataset of 706 samples covering a large range of COD concentration from 65 lakes and reservoirs in China, the high-precision linear relationship models between chromophoric dissolved organic matter (CDOM) absorption coefficient at 350 nm and 254 nm and COD concentration are constructed. In addition, the threshold and standard of CDOM absorption coefficient used to assess the surface water environmental quality was determined. Our linear models can be widely used to accurately and quantitatively characterize organic matter concentration and assess pollution degree in different types (deep and shallow water, large, medium and small area) and different trophic states (oligotrophic, mesotrophic, and eutrophic) of lake and reservoir waters with certain universality. By comparing the advantages and disadvantages of CDOM absorption coefficient and traditional COD measurement methods of potassium permanganate and potassium dichromate, this study demonstrates the feasibility and application prospect using CDOM absorption coefficient to substitute COD concentration for characterizing organic matter quantity and assess the pollution degree in lakes and reservoirs.

Relationship between Instant Sampling and Daily Average Values of COD for Urban Wastewater Treatment Plants in China

Most guidelines for urban wastewater treatment plants (WWTPs) are established on a time basis determination to determine performance and compliance with discharge standards and limits (i.e., maximum daily-average). Nevertheless, there is a lack of a systematic analysis of the relationship between instant sampling and daily average discharge concentration values. The present study used the chemical oxygen demand (COD) automated monitoring data that were collected from 1738 WWTPs in China to discuss the relationship between instant sampling and daily average values. A ratio model (K value) was developed to study the relationship between the reliability of the instant sampling value and the daily average limit for the COD measurements. The K value revealed that the ratio of COD instant and daily average measured concentrations for WWTPs in China collectively ranged from 1.00 to 1.45. The results of this study suggest setting the K value of COD to 1.3 for WWTPs in China to estimate the corresponding instant sampling limit of COD, as well as for most WWTPs in China, in order to ensure the stability of compliance to the daily average limits. The instant sampling value of COD in 24 h should be controlled no more than five times out of the instant sampling limit, which is 1.3 times of the daily average limit.

Performance of oat hulls activated carbon for COD and color removal from landfill leachate

This research aimed to recover oat hulls as activated carbon, using the produced adsorbent to remove the organic matter removal from landfill leachate. The organic matter content in leachate was determined by measurements of chemical oxygen demand (COD) and color. In addition, the maximum adsorptive capacities associated with the adsorbents were also determined. Adsorption batch tests were initially performed with synthetic leachate, and variables such as pH, activated carbon dose, temperature and contact time were evaluated. The effectiveness of the adsorbents was also verified for real landfill leachate. Oat hulls samples were chemically activated with phosphoric acid (impregnation ratios, 60 and 100 %) and pyrolyzed (N2 atmosphere) at 350 and 500 °C. The 100% impregnation ratio resulted in adsorbents with higher surface areas (1090–3880 m2 g−1) rather than the ratio 60 % (123–731 m2 g−1). It was found that the organic matter removal from synthetic leachate was favored by performing the adsorption tests at 20 °C, pH 4, and using a 20-g L−1 activated carbon dose. Under these experimental conditions, the activated carbon sample impregnated at 100% with phosphoric acid and pyrolyzed at 500 °C completely removed the color from leachate, and COD removal was up to 90%. Therefore, oat hulls comprise a suitable precursor for activated carbon, and its application for leachate treatment should be encouraged.

Real-time and hazard-free water quality monitoring based on microwave planar resonator sensor

This manuscript presents the development of a microwave microfluidic sensor for monitoring organic contaminants in water. This method offers a contactless, non-intrusive, and real-time monitoring system. The sensor is comprised of a compact double-ring resonator integrated with a 3D-printed microfluidic channel, operating at 4.5∼4.6 GHz with a quality factor of 120. The channel configuration on the resonator ensures maximum interaction between the electromagnetic field and the liquid sample and provides high sensitivity and resolution. The developed sensor was used to monitor organics (glucose, acetate and glucose-acetate mix) and the chemical oxygen demand (COD) standard (potassium hydrogen phthalate) in concentrations ranging from 50 to 800 mg/L as COD. The feasibility, reproducibility, and accuracy of the sensing platform was further validated by analyzing the S21 characteristic of the sensor. A monotonic decrease in the resonant amplitude of S21 was observed as the concentration of organics increased, with the sensitivity of 0.603 dB/COD [g/L], 0.087 dB/COD [g/L], 0.099 dB/COD [g/L] and 0.077 dB/COD [g/L] for potassium hydrogen phthalate, sodium acetate, glucose, and a glucose- acetate mixture, respectively. The findings support the capability of the microwave microfluidic sensor to detect dielectric properties variation associated with a minimum concentration of 17 mg/L glucose in water in real time. The response of the sensor was compared with conventional COD measurements using potassium dichromate digestion to compare the efficiency of the developed sensor with the spectrophotometric method to measure COD.

Removal of the Rhodamine B Dye at Ti/Ru0.3Ti0.7O2 Anode Using Flow Cell System

The electrochemical oxidation of the Rhodamine B dye (Rh-B) was carried out using dimensionally stable type anode (DSA, Ti/Ru0.3Ti0.7O2). The work was performed using the electrochemical flow cell system. The effect of several operating factors, such as supporting electrolytes, current density, electrolysis time, temperature, and initial concentration of Rh-B dye, were investigated. The UV-visible spectroscopy and chemical oxygen demand (COD) measurements were conducted to monitor the removal and degradation of Rh-B. The best color removal achieved was found to be 98.3% after 10 min applying 3.9 mA·cm−2 as a current density using 0.07 mol·L−1 of NaCl. Meanwhile, the highest COD removal rate (93.0%) was obtained for an applied current density of 3.9 mA·cm−2 as the optimal operating condition after 180 min reaction time, with 2.98 kW h·m−3 as energy consumption. This shows that the best conditions for color removal are not certainly the same as those for the COD removal. The rises in the concentration of NaCl, and applied current increased the Rh-B color removal rate. The decline in Rh-B dye concentration followed pseudo-first-order kinetics. The obtained values of apparent rate constant were increased by increasing chloride ion concentration. It is concluded that the electro-oxidation on DSA electrode using a flow cell is a suitable process for the removal of Rh-B dye in aqueous solutions.

Influence of Cu + g-C3N4 incorporation on the photocatalytic dye decomposition of ZnO film coated on stainless steel wire meshes

The present study is aimed to enhance the photocatalytic dye degradation efficiency of ZnO thin film by suitably adding copper + graphitic carbon nitride (Cu + g-C3N4). The thin films were deposited on flexible stainless steel substrates using nebulizer spray method. The prepared samples were subjected to XRD, PL, FTIR, DRS, SEM, HRTEM, EDAX and XPS studies to analyze how the addition of Cu + g-C3N4 changes the structural, optical and surface morphological properties of ZnO films which in turn influences its photocatalytic ability. The band gap values were found to be reduced from 3.29 to 2.83 and 2.53 after adding Cu and Cu + g-C3N4, respectively. To evaluate the role of active species, quenching experiments have been done. The mineralization of dye molecules was confirmed by chemical oxygen demand (COD) measurements. The present study addresses the mechanism behind the enhancement of photocatalytic dye degradation against Methylene Blue (MB) dye with authentic support from the characterization studies and relevant literature. The experimental results are verified using density functional theory (DFT) calculations.

An order determination method in direct derivative absorption spectroscopy for correction of turbidity effects on COD measurements without baseline required.

In chemical oxygen demand (COD) measurements based on ultraviolet-visible spectroscopy, turbidity interference represents a difficult technical problem. Common methods need the spectrum of real turbidity particles as the baseline, but it is inconvenient and vain to obtain because it changes with perturbation. Due to lack of theoretical guidance, the direct derivative method with no need of baseline was rarely used. Here in, we studied the absorption spectra of turbidity particles in series of samples and proposed an order determination method in the` direct derivative. In turbidity interference handling, the absorbance derivative of turbidity at each wavelength fell to zero by determining the appropriate derivative order. Two parameters were presented for order determination, which represented the overall size of particles and its scattering type based on the spectral shape and profile. Experiments showed that the formazine solution, as an extreme situation, had the largest parameters, so the derivative order was determined depending on it to ensure effective turbidity correctionin various real water samples. Through comparing the correction effects and COD prediction results of first-to-fourth order derivative spectra, the proposed method was verified to provide theoretical basis of direct derivative method and reduce blindness in the order determination.

Photocatalytic degradation of phenol using ionic liquid stabilized TiO2 nanoparticles

This paper describes the successful synthesis of ionic liquid stabilized TiO2 and it was characterized by various instrumental techniques such as UV–vis, FT-IR, XRD and TEM analysis. The photocatalytic activity of ionic liquid stabilized TiO2 nanoparticles (TiO2 NPs) was evaluated by analyzing the degradation of aqueous phenol solution by UV irradiation. The effect of phase composition of TiO2 NPs namely, anatase and rutile, on photocatalytic activity was studied using chemical oxygen demand (COD) and fluorescence measurements. The results show that pure anatase phase shows lesser photocatalytic activity compared to a mixed anatase: rutile phase (80:20) and the degradation mechanism is also investigated. The remarkable point is that the ionic liquid tunes the phases of the TiO2 NPs and this work provides a promising approach to fabricate TiO2 based catalyst with efficient photocatalytic performance.