Electrochemical detection of oxytetracycline employing sugarcane carbon modified graphite electrode.

The present study used CeO2-Co3O4 quantum dots@porous carbon/multiwalled carbon nanotube (CeO2-Co3O4 QDs@PC/MWCNT/GE) composites to modify graphite electrodes to fabricate high-sensitivity electrochemical sensors to detect the presence of oxytetracycline (OTC). The quantum dots were made from waste sugarcane bagasse. The electrochemical analysis demonstrated the superior electrochemical performance of CeO2-Co3O4 QDs@PC/MWCNT/GE, with a peak current density of 1.276 mA/cm2. Electrochemical impedance spectroscopy (EIS) revealed lower impedance values for CeO2-Co3O4 QDs@PC/MWCNT/GE compared to other electrodes, indicating enhanced conductivity. The modified electrode exhibited an enlarged electrochemically active area, with values of 0.602 cm2, almost seven times that of the bare graphite electrode (0.079 cm2). The results showed that the CeO2-Co3O4 QDs@PC/MWCNT/GE had excellent performance for OTC detection, and its linear calibration range was 1.007 × 10-8 to 2.04 × 10-7 M (i.e., 0.005-0.1 ppm) and 1.007 × 10-6 to 1.209 × 10-4 M (i.e., 0.5-60 ppm). The limit of detection and limit of quantification were 1.23 nM (0.61 ppb) and 4.09 nM (2.03 ppb) (S/N = 3), respectively. The electrode demonstrated long-term stability for up to 7 weeks. This method provides a new way to prepare electrochemical sensors for OTC detection.

Novel design of amine and metal hydroxide functional group modified onto sludge biochar for arsenic removal.

This study involved novel-designed sludge biochar (SB) adsorbed for arsenic removal with lower operating costs and higher adsorption efficiency properties. Generally, biochar only relies on micropores for pollutant adsorption, but physical adsorption is not highly efficient for arsenic removal. Therefore, in order to improve the removal efficiency of arsenic by SB, diethylenetriamine (DETA) and FeCl3 were used in this study to modify the surface of SB by an immersion method. The objectives of this research are to obtain optimum operation conditions by assessing the effect of different Fe content, pH and initial concentration on adsorbing arsenic. This study is the first to use Density Functional Theory (DFT) to simulate and verify the adsorption mechanism of arsenic by SB. Results showed the presence of amine/iron oxyhydroxides functional groups greatly promoted SB surface activity and its arsenic adsorption potential. The surface area, pore volume and pore size of the SB were estimated to be 525 m2 g-1, 0.35 cm3 g-1 and 8.71 nm, respectively. The DFT model result is the same as the result of arsenic adsorption performance with high adsorption energy (-246.3 kJmol-1) and shorter bond distances (1.42 Å), indicating strong chemical adsorption between arsenic and material. The reaction mechanism is divided into four pathways, including oxidation-reduction, complexation, electrostatic adsorption and pore adsorption.

Preparation of Metal Modified onto Biochar from Hazardous Waste for Arsenic Removal.

Use of urban sludge, hospital sludge, and aquatic product sludge as a biochar adsorbent from wastewater treatment plants was investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated at high temperatures to increase porosity and surface area. Effective of arsenic adsorption in water presents a newly designed metal doped to biochar. The biochar was characterized by scanning electron microscope (SEM) with energy dispersive X-ray (EDS), nitrogen adsorption/desorption isotherm analyzer (BET), thermo gravimetric analysis (TGA) and X-ray diffraction (XRD) analysis. Results display uniform pore sizes and high surface area (>490 m²g-1) of the biochar. Thence, urban sludge, hospital sludge, and aquatic product sludge can be used as carbon sources. The highest amount of Fe, Mn, and Ni loading onto the biochar was determined to be 8.0%, 6.0% and 10.0%, respectively. All biochar samples have arsenic adsorption capacities positively correlated with initial concentration. The corresponding removal efficiency of As(V) is 98% and As(III) is 84% at pH 3 with an adsorption capacity of 4.12 and 3.6 mg g-1, respectively. The adsorption capacity of As(V) and As(III) clearly decreased in the presence of PO43- (2.34 and 1.46 mg g-1, respectively). Due to competition for adsorption sites, the PO43- can effectively reduce arsenic adsorption. The arsenic species adsorption-desorption recycles on biochar are also discussed.

Adsorption Configurations of Iron Complexes on As(III) Adsorption Over Sludge Biochar Surface.

Waste recycling and reuse will result in significant material and energy savings. In this research, usage of hospital sludge as a biochar adsorbent for wastewater treatment plants was investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated with ZnCl2to increase surface area and porosity. A newly designed iron metal doped sludge biochar carbon (SBC) has effective adsorption of inorganic arsenic (As(III), As2O3) in water. The findings clearly demonstrate the viability and utility of using hospital sludge as a source of carbon to generate SBC. The adsorption mechanism of As(III) on SBC's iron-metal-modified surface has been studied using density functional theory (DFT) to understand the impact of functional complexes on adsorption As(III). Tests showed physical as well as chemical adsorption of As(III) on Fe-SBC surface. Fe's involvement in functional complexes greatly fostered SBC surface activity and it's As(III) adsorption ability. The physical adsorption energies of As(III) with Fe functional complexes on the SBC surface were -42.3 KJ mol-1. Other hand, the chemical adsorption energies of As(III) on Fe-SBC surface was -325.5 KJ mol-1. As(III) is capable of interacting in a bidentate fashion with the dopants through the protonated oxygen atoms and this conformation of the cyclic structure is higher in the adsorption energy than the others.

Aqueous Oxytetracycline and Norfloxacin Sonocatalytic Degradation in the Presence of Peroxydisulfate with Multilayer Sheet-Like Zinc Oxide.

Multilayer ZnO sheet-like flakes were synthesized by a simple method of precipitation and characterized by the techniques of X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The findings are proven that the SEM images show the overall morphology of a single sheet-like ZnO nanostructure made from uniformly thick nano-sheets. In an aqueous environment, the acoustic ability of the prepared material was assessed using ultrasound (US) radiation to degrade oxytetracycline (OTC) and norfloxacin (NF). To increase the degradation efficiency, a US/ZnO/peroxodisulfate system was developed by introducing ammonium persulfate ((NH4)2S2O8) and sodium persulfate (Na2S2O8), exhibiting excellent synergistic effects. Result show the decomposition efficiency for NF removal with Na2S2O8 (64%) appeared to be slightly better than with (NH4)2S2O8 (56%). By contrast, the ultrasonic catalytic efficiency of Na2S2O8 (98%) was slightly better than that of (NH4)2S2O8 (94%) for OTC removal. The addition of scavengers to the US/ZnO/peroxodisulfate system through the NF and OTC results in the largest effect of holes. The degradation is considered to be often caused by holes. In this system, the Na2S2O8 can have two roles to increase the rate of degradation: (1) The SO4- formed by Na2S2O8 under ultrasonic irradiation directly degraded to norfloxacin on ZnO surface; and (2) S2O82- behaved as an electron acceptor, inhibiting recombination of electron hole pairs, enabling the development of more ·OH. Therefore, the synergistic effect significantly increases US/ZnO/peroxodisulfate sonocatalytic activity (Hu, S.B., et al., 2017. Aqueous norfloxacin sonocatalytic degradation with multilayer flower-like ZnO in the presence of peroxydisulfate. Ultrasonics Sonochemistry, 38(1), pp.446-454).

Preparation of Zn-Doped Amino Functionalized Biochar from Hazardous Waste for Arsenic Removal.

The utilization of sludge from Far Eastern Memorial hospital (New Taipei city, Taiwan) wastewater treatment plants as biochar adsorbent was investigated. The sludge was carbonized using microwave carbonization and then chemically activated at high temperatures by using ZnCl2 to enhance porosity and surface area. A newly designed Zndoped amino-functionalized sludge biochar (Zn-SBC-DETA) presents effective As adsorption in water. The adsorbent was characterized by nitrogen adsorption-desorption, scanning electron microscopy (SEM) and thermogravimetric analysis. Results show that the surface area and average pore volume of Zn-SBC-DETA are 525 m² g-1 and 0.35 cm³ g-1, respectively. SEM results reveal that Zn-SBC-DETA has uniform pore size. The highest adsorption efficiency of As(III) is 79% at pH 3 with an adsorption capacity of 0.84 mg g-1. In addition, the adsorption efficiency of As(V) is 98% at pH 3 with an adsorption capacity of 1.43 mg g-1. The adsorption data can be described well by the Langmuir model rather than by the Freundlich model The data show good compliance with the pseudo second-order equation, and the correlation coefficient for the linear plots is higher than 0.97. Combined with the As species after reacting with Zn-SBC-DETA, the As transformation and adsorption mechanism are also discussed.

Preparation of Fe-SBC from Urban Sludge for Organic and Inorganic Arsenic Removal.

In the process of water treatment adsorption has been proved to be the best, because of its significant advantages. It is recognized that recycling and reuse of waste can result in significant savings in materials cost. In this research, the adsorption of organic and inorganic arsenic using sludge biochar (SBC) made from urban sludge were analyzed. The sludge was carbonized using calciner carbonization and then chemically activated at high temperatures and a newly designed Fe-doped sludge biochar (Fe-SBC) presents effective As adsorption in water. Results show that the surface area and average pore volume of Fe-SBC are 498 m² g-1 and 0.33 cm³ g-1, respectively. The adsorption capacity of p-ASA, As(V) and As(III) on Fe-SBC was calculated as 5.47, 3.83 and 3.24 mg L-1, respectively. The adsorption capacity of As were obviously decreased in presence of PO3-4. After six times recycles of adsorption-desorption processes, the adsorption capacity of p-ASA, As(V) and As(III) on Fe-SBC obvious reduction.

Preparation and Photocatalytic Hydrogen Production of Pt-Graphene/TiO2 Composites from Water Splitting.

Hydrogen is considered as a promising energy source with its high energy yield, renewable, environment friendly properties. TiO2 modified with noble metal and nonmetal is widely used. In this study, Pt and graphene (GN) were used to modify TiO2 nanoparticles. GN/TiO2 (TG), Pt-TiO2 (PT), Pt-GN/TiO2 (PTG) was successfully synthesized by modified Hummers' method, alcohol thermal and photodeposition method, respectively. The characterizations of the synthesized catalysts by UV-vis/DRS, components analysis, XRD and TEM analysis were conducted. Results showed the maximum hydrogen production rate was approximately 4.71 mmol h-1 g-1 when the Pt content was 1.0 wt.%. Higher and lower than 1.0 wt.% of Pt loading content both result in low efficiency of hydrogen production. The situation of graphene is similar to Pt. The optimal ratio for grapheme is 10 wt.%. The highest hydrogen production rate is 6.58 mmol h-1 g-1 by 1.5 wt.% Pt-5 wt.% GN/TiO2 (1.5PTG5), which is about 1.4 and 2.2 times higher than that of Pt-TiO2 and GN/TiO2 binary composites, respectively. The utilization of low-cost graphene can reduce the use of noble metal Pt in photocatalytic hydrogen production. The mechanism of Pt-GN/TiO2 for the improved photocatalytic activity is proposed. 0.1 g L-1 is found to be the optimum catalyst concentration for optimal hydrogen production.

Hexamethyldisilazane Removal with Mesoporous Materials Prepared from Calcium Fluoride Sludge.

A large amount of calcium fluoride sludge is generated by the semiconductor industry every year. It also requires a high amount of fuel consumption using rotor concentrators and thermal oxidizers to treat VOCs. The mesoporous adsorbent prepared by calcium fluoride sludge was used for VOCs treatment. The semiconductor industry employs HMDS to promote the adhesion of photo-resistant material to oxide(s) due to the formation of silicon dioxide, which blocks porous adsorbents. The adsorption of HMDS (Hexamethyldisiloxane) was tested with mesoporous silica materials synthesized from calcium fluoride (CF-MCM). The resulting samples were characterized by XRD, XRF, FTIR, N2-adsorption-desorption techniques. The prepared samples possessed high specific surface area, large pore volume and large pore diameter. The crystal patterns of CF-MCM were similar with Mobil composite matter (MCM-41) from TEM image. The adsorption capacity of HMDS with CF-MCM was 40 and 80 mg g-1, respectively, under 100 and 500 ppm HMDS. The effects of operation parameters, such as contact time and mixture concentration, on the performance of CF-MCM were also discussed in this study.

Effects of Different Sacrificial Agents and Hydrogen Production from Wastewater by Pt-Graphene/TiO2.

The Pt and graphene (GN) were used to modify TiO2 nanoparticles. GN/TiO2, Pt-TiO2, Pt-GN/TiO2 were successfully synthesized by modified Hummers' method, alcohol thermal and photodeposition method, respectively. The characterizations of the synthesized catalysts by different characterization techniques, including N2 adsorption-desorption isotherm, fourier transform infrared spectroscopy (FTIR), inductively coupled plasma (ICP) technique and element analyzer (EA), respectively. In addition, different sacrificial agents (methanol, ethanol, n-propanol, i-propanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and glycerol) have been investigated. There is clearly a linear relationship between hydrogen production rate and the polarity of monohydric alcohols. According to the Langmuir-Hinshelwood results, the surface pseudo-first order rate constant k = 15.06 mmol h-1 g-1 and the adsorption coefficient k = 0.50 mol L-1 were obtained. The feasibility of hydrogen production from wastewater obtained from terephthalic acid industry was studied. After reusing the catalyst under the same experimental conditions, the hydrogen production rate has only slightly decreased for 3 more cycles, which indicated the stability of the synthesized catalysts.

Preparation of Zn-Doped Biochar from Sewage Sludge for Chromium Ion Removal.

Recycling and reuse waste can result in significant savings in materials and energy. In this study, the adsorption of Cr(VI) was analyzed using activated carbon (AC) and biochar (BSC) made from sewage sludge. BSC materials were synthesized using zinc chloride as an activator coupled with carbonized sewage sludge. Specific surface area, pore size distribution, and pore volume were determined by measuring nitrogen adsorption-desorption (BET). BSC morphology was measured using field-emission scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Results showed that the surface area and average pore volume of the BSC were 490 m2 g-1 and 0.8 cm3 g-1, respectively. SEM results revealed that BSC had uniform pore size. Effects of varying the initial Cr(VI) concentrations, pH values, and dosages of BSC on adsorption performance were also determined. Results showed that the maximum removal efficiency of Cr(VI) was above 99%, and adsorption capacity of 50% ZnCl2-BSC was 677 mg g-1.

Adsorption of Methyl Blue on Mesoporous Materials Using Rice Husk Ash as Silica Source.

It is recognized that recycling and reuse of waste can result in significant savings in materials and energy. In this research, the adsorption of methyl blue (MB) using waste rice husk ash (Rha) and mesoporous silica materials made from Rha (R-MCM) were analyzed. Mesoporous silica materials were synthesized using cetyltrimethyl ammonium bromide (CTAB) as a cationic surfactant and Rha as the silica source. The prepared samples were characterized by Brunnaur-Emmet-Teller (BET) adsorption isotherm analyzer and transmission electron microscope (TEM) analysis. The results showed the surface area of R-MCM materials was 1347 m2g-1 and the pore volume was 0.906 cm3g-1. TEM analysis showed that the mesoporous materials generally exhibited ordered hexagonal arrays of mesopores with a uniform pore size. The effects on adsorption performance under different initial dye concentrations, different pH values and different dosages of adsorbent were also studied. Both Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The results show that the maximum removal efficiency of MB more than 99%.

Preparation of Amine-Modified Polyacrylonitrile Fibers: Copper Removalin Aqueous Solution.

In this study, Polyacrylonitrile (PAN) fibers were prepared by a simple and effective electrospinning method. Subsequently, the PAN fibers were modified by diethylenetriamine (DETA) to produce aminated polyacrylonitrile (APAN) fibers. Finally, the adsorbability of copper ions on the surface of the fibers was examined in an aqueous solution. The characteristics of APAN fibers were analyzed using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD); The surface amination was confirmed by FTIR. The adsorption data fitted well with the Freundlich isotherm. Thermodynamic parameters of the adsorption process were calculated. The standard Gibb's free energy change, standard enthalpy change, and standard entropy change was -1.46 KJ/mol, -54.72 kJ/mol, and -178.75 kJ/mol/K, respectively. Furthermore, the results show that adsorption of copper onto APAN fibers were spontaneous and exothermic in nature. The equilibrium adsorption capacity of PAN fibers was only 0.10 mg g(-1) for 10 mg L(-1) of copper solution removal under pH 6 and 298 K. In contrast, the equilibrium adsorption capacity of APAN fibers was 45.05 mg g(-1) under the same conditions. The prepared APAN fibers exhibit high efficiency for Cu(II) removal from Waste water and may be used as a reference for future investigation.

Treatment of Volatile Organic Compounds with Mesoporous Materials Prepared from Calcium Fluoride Sludge.

Large amount of calcium fluoride sludge was generated by semiconductor industry every year. It also needs high requirement of fuel consumption using rotor concentrator and thermal oxidizer to treat VOCs. The mesoporous catalyst prepared by calcium fluoride sludge was used for VOCs treatment in this study. Acetone is a kind of solvent and used in a large number of laboratories and factories. The serious problems will be caused when it exposed to the environmental. Economic and practical technology is needed to eliminate this kind of hazardous air pollutant. In this research, the adsorption of acetone was tested with CF-MCM (mesoporous silica materials synthesized from calcium fluoride). The raw material was mixed with cationic cetyltrimethyl ammonium bromide (CTAB) surfactants, firstly. The prepared mesoporous silica materials were characterized by nitrogen adsorption and desorption analysis, transmission electron microscope (TEM), scanning electron microscopy (SEM), X-ray powder diffractometer (XRPD) and Fourier transform infrared spectroscopy (FTIR). The results showed that the surface area, large pore volume and pore diameter could be up to 862 m2 g(-1), 0.57 cm3 g(-1) and 2.9 nm, respectively. The crystal patterns of CF-MCM were similar with MCM-41 from TEM image. The adsorption capacity of acetone with CF-MCM was 118, 190, 194 and 201 mg g(-1), respectively, under 500, 1000, 1500 and 2000 ppm. Furthermore, the adsorption capacity of MCM-41 and CF-MCM was almost the same. The effects of operation parameters, such as contact time and mixture concentration, on the performance of CF-MCM were also discussed in this study.

Synthesis, Characterization and Application of N-Ti/13X/MCM-41 Mesoporous Molecular Sieves.

Di-n-butyl phthalate (DBP) is a type of phthalate ester. In recent years, an increasing number of studies have examined the removal of DBP. In this study we use a composite material of N-Ti/13X/MCM-41, synthesized by nitrogen, molecular sieve 13X, tetrabutyl orthotitanate and tetraethyl orthosilicate as raw materials, CTAB as a structural template and tetrabutyl titanate and urea under hydrothermal conditions. The optimized experimental conditions, such as the amount of material, reaction time, pH value and initial concentration were tested. The surface areas of N-Ti/13X/MCM-41 were found to be 664 m2g(-1). TEM micrographs revealed N-Ti/13X/MCM-41 is consisting of aggregates of spherical particles, similar with standard synthesized MCM-41 (Mobil Composition of Matter No. 41). Through photocatalytic degradation experiments, the optimum degradation efficiency of DBP was more than 90% at a pH 6.0 with catalyst dosing of 0.15 g L(-1).

Application of forward osmosis (FO) under ultrasonication on sludge thickening of waste activated sludge.

Forward osmosis (FO) is an emerging process for dewatering solid-liquid stream which has the potential to be innovative and sustainable. However, the applications have still been hindered by low water flux and membrane fouling when activated sludge is used as the feed solution due to bound water from microbial cells. Hence, a novel strategy was designed to increase sludge thickening and reduce membrane fouling in the FO process under ultrasonic condition. The results from the ultrasound/FO hybrid system showed that the sludge concentration reached up to 20,400 and 28,400 mg/L from initial sludge concentrations of 3000 and 8000 mg/L with frequency of 40 kHz after 22 hours, while the system without ultrasound had to spend 26 hours to achieve the same sludge concentration. This identifies that the presence of ultrasound strongly affected sludge structure as well as sludge thickening of the FO process. Furthermore, the ultrasound/FO hybrid system could achieve NH4+-N removal efficiency of 96%, PO4(3-)-P of 98% and dissolved organic carbon (DOC) of 99%. The overall performance demonstrates that the proposed ultrasound/FO system using seawater as a draw solution is promising for sludge thickening application.

Photocatalytic Degradation of Di-n-Butyl Phthalate by N-Doped Ti/13X/MCM-41 Molecular Sieve.

Di-n-butyl phthalate (DBP) is a type of phthalate ester, and has been classified as an environmental endocrine disruptor. It causes serious harm to the environment and humans and it is found widely in air, waste water, rivers and soil. In recent years, an increasing number of studies examined the removal of DBP. Photocatalytic degradation has been of particular interest because of its efficient and thorough advantages and is the focus of this study. Here we use a composite material of N-Ti/13X/MCM-41, synthesized, using 13X and tetraethyl orthosilicate as raw material, CTAB as structural template, tetrabutyl titanate and urea under hydrothermal conditions. The optimized experimental conditions, such as, Si/Al (molar ratio), pH value, crystallization time, calcination temperature and N/Ti (molar ratio), were tested using photodegradation experiments of DBP. The samples were characterized by XRD, TEM, FT-IR, N2 adsorption-desorption. Experimental results reveal the surface area of the N-Ti/13X/MCM-41 to be 664 m2 g(-1) and the average pore sizes to be 2.79 nm. TEM micrographs showed the N-Ti/13X/MCM-41 consists of aggregates of spherical particles, similar to the shapes associated with standard MCM-41 synthesized under basic conditions. Photocatalytic degradation experimental results revealed that optimal synthesis of the composite material occurs when Si/Al = 15, pH = 9.0, crystallization time is 48 hours, calcination temperature is 350 °C and the N/Ti ratios is 2.0. Under such conditions, the degradation efficiency of DBP more was found to be more than 90%.