Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash as modified papermaking fillers

Silica (SiO₂) nanoparticles and silica/calcium carbonate (SiO₂/CaCO₃) core–shell nanocomposites were prepared by sol–gel technique as fillers for papermaking application. Semi-burned rice straw ash (SBRSA), as waste material, was used to prepare the targeted fillers. Preparation of SiO₂ nanoparticles and SiO₂/CaCO₃ nanocomposites was carried out using Na₂SiO₃ solution that was prepared from SBRSA and CaCO₃ nanoparticles of 30–70 nm. The targeted SiO₂/CaCO₃ nanocomposites were prepared with different molar ratio of SiO₂:CaCO₃ 1:15, 1:10 and 1:5. The percentage of silica increased from 62.5% to 82.9% by thermal treatment of SBRSA at 800 °C for 2 h. The prepared SiO₂ nanoparticles and SiO₂/CaCO₃ nanocomposites were characterized by using XRD, XRF, TEM, FT-IR and Zeta potential. The results indicate that a pure semi-crystalline SiO₂ nanoparticle and semi-crystalline shell of SiO₂ coated CaCO₃ core particles were produced. The work extended also to investigate the effect of the prepared fillers on physical, mechanical and optical properties of paper.Application of the prepared SiO₂ nanoparticles and SiO₂/CaCO₃ nanocomposites improved the optical properties of paper (brightness, whiteness and opacity) but it slightly reduced the mechanical properties when compared to commercial precipitated CaCO₃ (PCC) filler.The results showed that the retention of SiO₂ nano-particles was highly increased. The retention of the prepared nanocomposites increased along with increasing of SiO₂:CaCO₃ molar ratio.     

Efficient photocatalytic treatment of sugar mill wastewater with 2%Ag3PO4/Fe/GTiP nanocomposite

The large amount of colored substances exist in the sugar mills wastewater that give higher organic load to the effluent. Therefore, a novel study of sugar mill wastewater treatment was carried out under photocatalysis by using a nanocomposite of silver phosphate-iron-graphene oxide-titanium phosphate (Ag₃PO₄/Fe/GTiP). The catalyst was prepared by simple chemical process with 2% content of Ag₃PO₄ to Fe/GTiP. The light, catalyst dosage, pH, and scavenger impacts on the decolorization and chemical oxygen demand (COD) removal from the sugar mill wastewater were observed. The highest decolorization and COD removal of 85.02% and 80.3% was achieved under pH-1 by using 50 W visible halogen light at catalyst dosage of 100 mg/75 ml in 200 min. The excellent recycled results were observed up to four cycles. The obtained results proves that this catalyst has high photocatalytic efficiency to treat the sugar mill wastewater.     

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics,efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al₂O₃ was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O₂^–, and ¹O₂), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al₂O₃ catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ～ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ～ 0.032$/m³, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al₂O₃ exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.     

Effect of organic and inorganic compounds on dissolution kinetics of chalcopyrite in hydrogen peroxide– Hydrochloric acid system

The addition of 2-Propanol as an organic substance and NaCl as an inorganic compound in hydrochloric acid with hydrogen peroxide as a strong leaching agent of chalcopyrite was investigated. The effects of the leaching parameters on copper extraction, such as stirring speed, H₂O₂ concentration, temperature, HCl concentration and solid/liquid ratio were studied. The maximum final copper extraction of 54.55% was obtained with 600 rpm stirring speed, 1.5 M H₂O₂, 0.5 M HCl, 600 rpm, 50 °C, 240 min of the reaction and particle size of ?106 +75 µm. Further experiments were performed when the solid-to-liquid ratio (S/L), stirring speed, temperature, HCl, H₂O₂ and leaching time were kept constant to examine the influence of NaCl and 2-Propanol concentrations in the range of 0–0.5 M and 0–3 M, respectively. The results showed that the copper extraction was increased up to 58.11% with addition of NaCl. While copper extraction yield reached 94.25% in case of addition of 2-propanol with the optimum parameters(0.5 M HCl,50 °C, 1.5 M H₂O₂, 600 rpm, particle size ?106 +75 μm, solid liquid ratio 2g/L, 3 M 2-propanol). The chalcopyrite leaching in hydrogen peroxide– hydrochloric acid system was found to be described by the interface transfer and diffusion across the product layer with activation energy of 77.14 kJ/mol. Addition of 2-propanol suggested that the reaction was under product layer diffusion control and decreased the activation energy of chalcopyrite leaching to 67.98 kJ/mol.     

Electrochemical degradation of 2,4-Dinitrotoluene (DNT) from aqueous solutions using three-dimensional electrocatalytic reactor (3DER): Degradation pathway,evaluation of toxicity and optimization using RSM-CCD

2,4-Dinitrotoluene (2,4-DNT) has been found to be an important petrochemical compound, which is primarily employed for the synthesis of tolylene diisocyanate and the production of dyes, rubber, and explosives. Since this compound has high toxicity and carcinogenicity, the cautions should be considered when wastewater contaminated with DNTs and their derivatives is released into the environment. Thus, the object of the present study was the investigation of the 2,4-DNT degradation efficiency using the three-dimensional electrocatalytic reactor (3DER) with two different types of particle electrodes (granular activated carbon (GAC) and magnetized clinoptilolite zeolite (MCZ)@Fe₃O₄ nanoparticles)). Preparation of the graphite (G)/β-PbO₂ anode was done by electrochemically depositing PbO₂ layers on graphite sheets. The prepared graphite sheet and a stainless-steel 316 sheet (with the same dimensions) were employed as the anode and the cathode, respectively. Field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), and energy-dispersive X-ray spectroscopy mapping (EDS-mapping) confirmed the successful preparation of G/β-PbO₂ anode. The surface morphology, chemical composition of MCZ@Fe₃O₄ nanoparticles as a particle electrode were determined by scanning electron microscope (SEM) and XRD pattern. To determine the optimal conditions, we employed the response surface methodology-based central composite design (RSM-CCD) method. According to observed results, higher efficiency of 3DER was obtained by increasing the reaction time and current density and decreasing pH and the pollutant concentration. Studies highlighted the initial 2,4-DNT concentration of 23.5 mg/L, current density 4.8 mA/cm², pH of 4.1, electrolysis time of 50 min, particle electrodes dose = 6 g/250 cc as optimum values of parameters. The 2,4-DNT degradation efficiencies using GAC and MCZ@Fe₃O₄ nanoparticles as particle electrodes under mentioned optimal conditions were 98.6% and 96.5%, respectively. Moreover, the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies were 88.5% and 80.9% at the end of 50 min, respectively. Furthermore, results were indicative of an enhancement in average oxidation state (AOS) (from 1.27 to 2.36) and carbon oxidation state (COS) (from 1.27 to 3.68) in the 3DER process and a reduction in the COD/TOC ratio (from 1.81 to 1.09); these signposts the effectiveness of 3DER system for providing the biodegradability of 2,4-DNT. Considering the results, the 3DER could lead to suitable results for the degradation of wastewater containing DNT and resistant contaminants as pretreatment and has remarkable applicability for enhancing the biodegradability of wastewater.     

新型球形纳米空心SiO2的模板合成方法研究

以纳米碳酸钙颗粒为新颖的无机模板剂, 硅酸钠为无机硅源, 通过溶胶-凝胶法形成CaCO₃/SiO₂的核壳结构; 随后通过高温煅烧、酸溶和干燥处理, 合成出了具有高比表面积的球形纳米空心二氧化硅粒子. 然后, 分别采用TEM, SEM, EDS, XRD, FTIR和TG等测试手段对样品进行了分析和表征, 并考察了不同合成条件, 如反应温度、反应pH值、煅烧温度和包覆反应时SiO₂/CaCO₃的配比对纳米空心二氧化硅粒子的比表面积变化. 实验结果表明: 较高的反应温度如60～80 ℃, pH值9左右、SiO₂包覆量为碳酸钙质量的10%, 以及煅烧温度为700 ℃, 有利于形成空心形貌较好、比表面较大的球形纳米空心二氧化硅.     

Thermal stability and UV-shielding properties of polymethyl methacrylate and polystyrene modified with calcium carbonate nanoparticles

The influences of nanosized CaCO₃ on the thermal and optical properties embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) were investigated. Calcium carbonate nanoparticles were synthesized by in situ deposition technique, and its nano size (32–35 nm) was confirmed by scanning electron microscope (SEM) and X-ray studies. Nanocomposites samples of PMMA/CaCO₃ and PS/CaCO₃ were prepared with different filler loading (0–4 wt%) of CaCO₃ nanoparticles by solution mixing technique. The Fourier transform infrared analysis confirmed that CaCO₃ nanoparticles were present in the polymers matrices. The morphology and elemental composition of nanocomposites were evaluated by SEM and energy dispersive X-ray spectroscopy. The thermal properties of nanocomposites were characterized by differential scanning calorimetric, thermogravimetric, and differential thermogravimetry analysis, and the results indicate that the incorporation of CaCO₃ nanoparticles could significantly improve the thermal properties of PMMA/CaCO₃ and PS/CaCO₃ nanocomposites. The glass transition temperature (T _g ) and decomposition temperature (T _d ) of nanocomposites with 4 wt% of CaCO₃ nanoparticles were increased by 30 and 24 K in case of PMMA/CaCO₃ and 32  and 15 K in the case of PS/CaCO₃ nanocomposites, respectively. The obtained transparent nanocomposites films were characterized using UV–Vis spectrophotometer which shows the transparencies of nanocomposites are almost maintained in visible region while the intensity of absorption band in ultraviolet (UV) region is increased with CaCO₃ nanoparticles contents and these composites particles could enhance the UV-shielding properties of polymers.     

Assessment of copper(II) biosorption from aqueous solution by agricultural and industrial residues

In this study, newspaper scraps (NS) and maize spatha (MS) treated in turn by HNO₃ and MeOH were evaluated for the biosorption of Cu²⁺ ions, on the basis of batch experiments. The effects of several parameters were investigated, including contact time, solution pH, shaking speed, biosorbent dosage and ionic strength. Under optimal conditions, the maximum sorption capacities (Q_max) were (60.386 ± 0.006) and (44.90 ± 0.02) μmol Cu²⁺ per g of sorbent, respectively, for NS and MS chemically treated with HNO₃. The optimal parameters were pH: 5, contact time: 40 min and shaking speed: 100 rpm for NS, while for MS the same parameters were pH 5, 20 min and 150 rpm, respectively. It was found that Cu²⁺ biosorption is disfavored by an increase in ionic strength and by the presence of some interfering cations. The experimental data obtained with NS best matched the Langmuir’s sorption model (R² = 0.994) while the Temkin model best described biosorption on MS (R² = 0.987). The biosorption of Cu²⁺ on both materials followed pseudo-second order kinetics, and the desorption of Cu²⁺ ions was effective in 0.01 M HCl solution.     

Coagulation and UF treatment of pulp and paper mill wastewater in comparison

A study using coagulation-flocculation and ultrafiltration (UF)methods for pulp and paper mills’ wastewater (WW)was carried out. The reduction efficiencies of turbidity and chemical oxygen demand (COD), the removal efficiency of total suspended solids (TSS) and absorbance at 254 nm were the main evaluating parameters. Using coagulation-flocculation, the efficiencies of alum and polyaluminum chloride (PACl)were studied, when used alone and when coupled with flocculant aids. During the coagulation-flocculation process, use of a single coagulant, the coagulant dosage, and the pH, play an important role in determining the coagulation efficiency. At the optimum PACl dosage of 840 mg L⁻¹ and optimum pH of 9.0, turbidity reduction was found to be 94.5%. A combination of inorganic coagulant and flocculant, or polymer was applied, in which PACl was used coupled with the polyelectrolytes Organopol WPB20 and WPB40. PACl coupled with Organopol WPB20 by optimal pH 9 gave a 98.3% reduction of turbidity, 91.9% removal of TSS, and a 60.2% reduction in COD. Ultrafiltration trials were carried out on a pilot scale. A tubular module was used with ceramic membrane. This membrane is a multi-channel membrane with an active surface layer made of Al₂O₃ and ZrO₂. Within the acidic range, the turbidity and TSS were removed at above 99%.     

Cinnamon zeylanicum bark extract and powder mediated green synthesis of nano-crystalline silver particles and its bactericidal activity

The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology as it does not involve any harmful chemicals. The present study reports the synthesis of silver (Ag) nanoparticles from silver precursor using the bark extract and powder of novel Cinnamon zeylanicum. Water-soluble organics present in the plant materials were mainly responsible for the reduction of silver ions to nano-sized Ag particles. TEM and XRD results confirmed the presence of nano-crystalline Ag particles. The pH played a major role in size control of the particles. Bark extract produced more Ag nanoparticles than the powder did, which was attributed to the large availability of the reducing agents in the extract. Zeta potential studies showed that the surface charge of the formed nanoparticles was highly negative. The EC₅₀ value of the synthesized nanoparticles against Escherichia coli BL-21 strain was 11 ± 1.72 mg/L. ThusC. zeylanicum bark extract and powder are a good bio-resource/biomaterial for the synthesis of Ag nanoparticles with antimicrobial activity.     

Influence of pH on the incorporation and growth of Pb<Subscript>2</Subscript>CrO<Subscript>5</Subscript> crystallites in silica matrix

Pb₂CrO₅ nanoparticles were embedded in an amorphous SiO₂ matrix by the sol–gel process. The pH and heat treatment effects were evaluated in terms of structural, microstructural and optical properties from Pb₂CrO₅/SiO₂ compounds. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS), and diffuse reflectance techniques were employed. Kubelka–Munk theory was used to calculate diffuse reflectance spectra that were compared to the experimental results. Finally, colorimetric coordinates of the Pb₂CrO₅/SiO₂ compounds were shown and discussed. In general, an acid pH initially dissolves Pb₂CrO₅ nanoparticles and following heat treatment at 600 °C crystallized into PbCrO₄ composition with grain size around 6 nm in SiO₂ matrix. No Pb₂CrO₅ solubilization was observed for basic pH. These nanoparticles were incorporated in silica matrix showing a variety of color ranging from yellow to orange.     

Breakup promotion of deformed EPDM droplets by the migration of nanoparticles during extrusion

The effect of migration of calcium carbonate (CaCO₃) nanoparticles on the breakup dynamics of Ethylene-Propylene-Diene Monomer (EPDM) droplets in Polypropylene (PP) matrix during melt extrusion was investigated in situ. The breakup process of EPDM droplets was sped up dramatically when the migration of CaCO₃ nano-particles from dispersed phase to matrix was introduced to PP/EPDM melts. It was found that both the total breakup time and the shape stability of slender EPDM droplets decreased with the increase of CaCO₃ concentration. Both the maximum value in equivalent diameter d and aspect ratio AR of EPDM droplets were also reduced by increasing the composition of CaCO₃ nanoparticles. Results were discussed in consideration of interfacial tension and migration of CaCO₃ nanoparticles. Reduction in interfacial tension is mainly responsible for the improved breakup process in the two-step composites with CaCO₃ nanoparticles (<2 wt%). Higher composition of CaCO₃ (≥2 wt%) induced the CaCO₃ aggregates in the EPDM phase. These aggregates acted as stress concentration when the EPDM droplets break up.     

Feasibility of treating swine manure in an anaerobic sequencing batch biofilm reactor with mechanical stirring

Anaerobic sequencing batch reactors containing granular or flocculent biomass have been employed successfully in the treatment of piggery wastewater. However, the studies in which these reactors were employed did not focus specifically on accelerating the hydrolysis step, even though the degradation of this chemical oxygen demand (COD) fraction is likely to be the limiting step in many investigations of this type of wastewater. The mechanically stirred anaerobic sequencing batch biofilm reactor offers an alternative for hastening the hydrolysis step, because mechanical agitation can help to speed up the reduction of particle sizes in the fraction of particulate organic matter. In the present study, a 4.5-L reactor was operated at 30°C, with biomass immobilized on cubic polyurethane foam matrices (1 cm of side) and mechanical stirring provided by three flat-blade turbines (6 cm) at agitation rates varying from 0 to 500 rpm. The reactor was operated to treat diluted swine waste, and mechanical stirring efficiently improved degradation of the suspended COD. The operational data indicate that the reactor remained stable during the testing period. After 2 h of operation at 500 rpm, the suspended COD decreased by about 65% (from 1500 to 380 mg/L). Apparent kinetic constants were also calculated by modified first-order expressions.     

Enhancement of water barrier properties and tribological performance of hybrid glass fiber/epoxy composites with inclusions of carbon and silica nanoparticles

Water barrier properties and tribological performance (hardness and wear behavior) of new hybrid nanocomposites under dry and wet conditions were investigated. The new fabricated hybrid nanocomposite laminates consist of epoxy reinforced with woven and nonwoven tissue glass fibers and two different types of nanoparticles, silica (SiO₂) and carbon black nanoparticles (C). These nanoparticles were incorporated into epoxy resin as a single nanoparticle (either SiO₂ or C) or combining SiO₂ and C nanoparticles simultaneously with different weight fractions. The results showed that addition of carbon nanoparticles with 0.5 and 1 wt% resulted in maximum reduction in water uptake by 28.55% and 21.66%, respectively, as compared with neat glass fiber reinforced epoxy composites. Addition of all studied types and contents of nanoparticles improves hardness in dry and wet conditions over unfilled fiber composites. Under dry conditions, maximum reduction of 47.26% in weight loss was obtained with specimens containing 1 wt% carbon nanoparticles; however, in wet conditions, weight loss was reduced by 17.525% for specimens containing 0.5 wt% carbon nanoparticles as compared with unfilled fiber composites. Diffusion coefficients for different types of the hybrid nanocomposites were computed using Fickian and Langmuir models of diffusion. Copyright © 2017 John Wiley & Sons, Ltd.     

Optimization of multiple parameters for treatment of coking wastewater using Fenton oxidation

Present study deals with the treatment of coking wastewater (CWW) using Fenton oxidation process for the degradation of pollutants containing chemical oxygen demand (COD), phenol and cyanide. The experiments were performed in batch mode to study the effect of operating parameters like initial pH (pH_i), temperature (T), oxidant H₂O₂ amount, catalyst mass loading (Cw) and treatment time (t_R). The response surface methodology (RSM) gave optimum value of pH, H₂O₂, Cw and t_R as 3, 0.3 M, 1.85 g/L (0.0266 M) and 1.52 h. At this optimum operating condition maximum 84.66% COD, 88.46% phenol and 79.34% cyanide reduction were achieved from initial value of COD (COD_i) = 2810.0 mg/L, phenol_i = 283.0 mg/L and cyanide_i = 18.88 mg/L. Results reflect that Fenton oxidation is an effective process for the reduction of pollutants present in CWW. The CWW treated by Fenton oxidation having average value COD = 590.0 mg/L, phenol = 39.49 mg/L and cyanide = 5.2 mg/L was further treated by adsorption process as second stage treatment, and these values were reached to COD = 199.0 mg/L, phenol = 0.0 mg/L and cyanide = 2.36 mg/L. The response surface methodology (RSM) was used for the designing and optimization of the experiments. Analysis of variance (ANOVA) suggested the high regression coefficient R² = 0.999 and 0.993 for COD and phenol removal respectively. The two stage treated CWW can be recycled and reused in same industry for various purpose.     

Enhancement of Cd2+ removal on CuMgAl-layered double hydroxide/montmorillonite nanocomposite: Kinetic,isotherm, and thermodynamic studies

In recent decades, great progress has been made in the application of adsorption processes to mitigate water pollution by hazardous metals. However, developing a highly efficient adsorbent is essential if the adsorption process is to be successfully applied in practical applications. In this study, a CuMgAl-layered double hydroxides/montmorillonite nanocomposite (CuMgAl-LDH/MMt) was prepared, characterized, and then used as a novel adsorbent for adsorption of Cd²⁺ ions from wastewater. The effects of initial pH, adsorbent dosage, agitation speed, particle size, contact time, initial Cd²⁺ concentration, and temperature on the pollutant removal efficiency were analyzed. An isotherm model reading revealed that the results of the experimental work were a good fit with the Freundlich model. The maximum adsorption capacity was reached at 174.87 mg/g under optimal conditions (pH 5, dosage of 0.02 g/l, agitation speed of 150 rpm, and particle size of 87 μm) at 50 ppm after 120 min of adsorption time. Kinetic studies showed that pseudo-second-order models were best fitted to the adsorption data, indicating heterogeneous adsorption of Cd²⁺ ions onto multilayer CuMgAl-LDH/MMt sites, and that the adsorption process is primarily chemical adsorption. Thermodynamic parameters (ΔS^o, ΔH^o, and ΔG^o) demonstrated that Cd²⁺ adsorption onto adsorbent was exothermic and spontaneous. Moreover, the synthesized adsorbent can be recovered after five consecutive cycles with a minimal reduction in the adsorption ability of 29.56 %. The study showed that specific heavy metals can be removed from aqueous solution by a newly prepared adsorbent due to its excellent morphology, high stability under a wide range of conditions, recyclability, and high adsorption capacity.     

Optimising zero-valent iron from industrial waste using a modified air-Fenton system to treat cutting oil wastewater using response surface methodology

This study investigates the treatment of cutting oil wastewater from the automotive parts manufacturing industry to promote sustainability via the use of ‘used shot blasts’, which are the by-products of auto parts production. Used shot blasts are rich iron sources of Fe⁰, which becomes an effective catalyst in the Fenton reaction. A modified air-Fenton (MAF) system was proposed to generate hydroxyl radicals that eliminated recalcitrant organics in cutting oil wastewater. First, the Taguchi method, comprising the L18 orthogonal array design, was used to identify significant operation factors, including the size and amount of used shot blasts, initial pH, reaction time, mixing speed, initial cutting oil concentration, and air flow rate. Then, a central composite rotatable design coupled with response surface methodology (RSM) was used to determine the optimal conditions and model the influencing variables. The results provided three crucial variables for the cutting oil wastewater treatment through use of the MAF system: initial pH, the amount of used shot blasts, and initial cutting oil concentration. RSM was applied to reveal the optimum operating conditions, achieving a maximum removal efficiency of 92.82% for chemical oxygen demand (COD), 80.18% for total organic carbon (TOC), and 99.55% for turbidity within 45 min of operating the MAF system. The model agreed well with the experimental data, with coefficient of determination values of 0.9819, 0.9654, and 0.9715 for COD, TOC, and turbidity removal efficiency, respectively. Pseudo-second-order reaction kinetics fitted well for COD removal, with a rate constant of 0.0218 min^?1 and hydrogen peroxide generation of 0.0169 M. Overall, the proposed MAF system was efficient and had a low operating cost (0.67 USD/m³).     

Oxygen plasma-treated gold nanoparticle-based field-effect devices as transducer structures for bio-chemical sensing

EIS (electrolyte-insulator-semiconductor) sensors based on the functionalization of uncoated gold nanoparticles supported on a Si/SiO₂ structure are presented. Oxygen plasma etching at moderate power (<200 W) provides a convenient and efficient way to remove organic capping agents from the gold nanoparticles without significant damage. Higher power intensities destroy the linkage between the SiO₂ and the gold nanoparticles, and some of the gold nanoparticles are removed from the surface. The flat-band potential shift, i.e. the pH dependence of the gold-coated EIS sensors is similar (33 mV/pH) to the uncoated EIS pH-sensor. Lead, penicillin and glucose sensors were prepared by immobilization of β-cyclodextrin, penicillinase and glucose oxidase by various immobilization techniques.

     

Modification of nano-hybrid silicon acrylic resin with anticorrosion and hydrophobic properties

Silicone-acrylic resin (SAR) was prepared from acrylic monomers and silicone prepolymer by the free radical solution polymerization, and then mixed TiO₂ and SiO₂ nanoparticles modified by KH570 were added to prepare nanocomposite coating. Thermogravimetric analysis and contact angle measurements showed that the acrylic resin modified by silicone prepolymer exhibited an improved thermostability and a better hydrophobicity compared with the unmodified sample. The adding of nanoparticles further increased the hydrophobicity. The contact angle of modified silicone-acrylic resin with mixed TiO₂ and SiO₂ nanoparticles of 3 wt% is the highest, 108.4°. The UV resistance and weather resistance of the modified silicone-acrylic resin are significantly improved. It was also found through electrochemical impedance spectroscopy that the corrosion resistance was significantly improved by the addition of mixed TiO₂ and SiO₂ nanoparticles. Modified silicone-acrylic resin with mixed TiO₂ and SiO₂ nanoparticles of 3 wt% and 5 wt% coating system maintains an excellent anticorrosion performance (coating resistance R_c of more than 10⁹ Ω cm²) even at 3.5% NaCl electrolyte medium till to 1800 h.     

Posttreatment of Olive Mill Wastewater by Immobilized TiO2 Photocatalysis

A photocatalytic reactor with UV/TiO₂ was used for the posttreatment of olive mill wastewater after anaerobic digestion. A factorial experimental design was adopted to determine the statistical significance of each parameter tested, namely, initial chemical oxygen demand (COD), pH, treatment time and recirculation flow and possible interactions in three response variables: phenols, color and COD removals. Removal efficiencies of 90.8 ± 2.7%, 79.3 ± 1.9% and 50.3 ± 6.3% were obtained for total phenols (TPh), color and COD respectively. TPh and color were almost completely removed after 24 h of treatment, while the COD removal was partial. Because increasing the treatment time is economically unfeasible a recirculation to the anaerobic reactor should be considered. Regarding the most significant variables, the TPh removal efficiency is dependent of the initial COD concentration; the color removal efficiency decreased with increasing COD concentration and pH; and, the COD removal efficiency is directly linked with the treatment time. The interaction between the initial COD and treatment time affect negatively the response variables tested because of the inactivation of some active sites of the TiO₂ paper.