Monireh Khadem, Farnoush Faridbod, Parviz Norouzi, Abbas Foroushani Rahimi Foroushani, Mohammad Reza Ganjali, Seyed Jamaleddin Shahtaheri, Rasoul Yarahmadi,
Volume 7, Issue 1 (4-2017)
Abstract
Diazinon is commonly used for pest control in the agricultural fields because of its relatively low cost and high efficiency. Due to the increasing application of pesticides, reliable and accurate analytical methods are necessary for their monitoring. This work was aimed to design the high selective electrochemical sensor for determining of diazinon in biological and environmental samples. The composition of sensor was modified with multi-walls carbon nanotubes and a molecularly imprinted polymer (MIP). A diazinon MIP was synthesized and applied in the carbon paste electrode (CP). The prepared sensor was used to determine the concentration of analyte. Parameters affecting the sensor response, such as sample pH, electrolyte concentration and its pH, and the instrumental parameters of square wave voltammetry, were optimized in different levels to select the optimum conditions for analysis of diazinon. The MIP-CP electrode showed very high specificity for determining the analyte. The obtained linear range was 1×10-6 to 5×10-10 mol L-1. The detection limit was 2.7×10-10 molL-1. This sensor was successfully used to determine the diazinon in environmental and biological real samples without special sample pretreatment before analysis.
Hojatolla Kakaei, Mojtaba Beygzadeh, Farideh Golbabaei, Mohammad Reza Ganjali, Mehdi Jahangiri, Sayed Jamaleddin Shahtaheri,
Volume 9, Issue 4 (12-2019)
Abstract
Introduction: Hydrogen sulfide is one of the most important impurities in natural gas. Due to the fact that this gas is hazardous, toxic, corrosive and volatile, therefore, the removal of hydrogen sulfide has been studied using several methods. One of the most known procedures is the adsorption process. In the present study, activated carbon and activated carbon-based composite scaffolds (MOF-5) were used as a cartridge mask to remove hydrogen sulfide from respiratory air.
Methods and Materials: First, activated carbon (AC) was converted to powder form by ball mill, and AC / MOF-5 composite with 10%, 25%, and 40% MOF-5 to AC was synthesized from the MOF-5 metal-organic scaffold. Then, the rates of adsorption and breakthrough time using a designed setup were tested in two ranges of temperatures, humidities and concentrations. XRD, SEM and BET were used to determine the properties of composite absorbents. The Aeroqual S500 Direct-reading sensor with 0.01 ppm accuracy was used to measure the exact amount of hydrogen sulfide gas.
Results: The AC/MOF-5 composite showed higher adsorption and breakthrough time compare to the other adsorbents. The Specific surface area (BET), average pore diameter, and total pore volume of the adsorbent were 814 m2 /g, 1.6795 nm, and 0.342 cm3 /g, respectively. The isotherm diagram showed that, according to IUPAC, most of the pore size of this adsorbent was classified in the micro-porous group. The maximum adsorption (mg/gS) and breakthrough time (min) were related to AC/MOF-5(40 Wt. %) adsorbent with 60.41 mg/gS (SD = 1.08) and 56.26 min (SD =2.38) at a temperature of 15 ° C, a concentration of 9.88 ppm (SD = 0.70), a moisture content of 51.06% (SD = 0.15) and a pressure drop of 51.34 mm water. By adding more than 25% MOF-5 metal-metal scaffold to activated carbon, the amount of adsorption, breakthrough time and pressure drop were increased.
Conclusion: AC / MOF-5 composite adsorbent due to its porous structure, high specific surface area, and most importantly, having Zn-O-C groups increased the adsorption rate as well as the pollutant Breakthrough time. However, it showed a relatively higher pressure drop than commercial activated carbon (AC).
