The mutual influence of Y⋯N and H⋯H interactions in XHY⋯NCH⋯HM complexes (X = F, Cl, Br; Y = S, Se; M = Li, Na, BeH, MgH): Tuning of the chalcogen bond by dihydrogen bond interaction

The equilibrium structures, interaction energies, and bonding properties of ternary XHY⋯NCH⋯HM complexes are studied by ab initio calculations, where X = F, Cl, Br, Y = S, Se, and M = Li, Na, BeH, MgH. The ab initio calculations are carried out at the MP2/aug-cc-pVTZ level. The results indicate that all optimized Y⋯N and H⋯H binding distances in the ternary complexes are smaller than the corresponding values in the binary systems. The calculated cooperative energies (Ecoop) are between -0.20 kcal/mol in BrHS⋯NCH⋯HBeH and -3.29 kcal/mol in FHSe⋯NCH⋯HNa. For a given Y and M, the estimated Ecoop values increase as X = F > Cl > Br. In addition, the selenium-bonded complexes exibit larger Ecoop values than those of the sulfur-bonded counterparts. The cooperativity between Y⋯N and H⋯H interactions is further analyzed by quantum theory of atoms in molecules and natural bond orbital methods. Cooperative effects make an increase in the J(Y-N) and J(H-H) spin-spin coupling constants of the ternary complexes with respect to the binary systems. © 2016 Published by NRC Research Press

Rapid removal of phenol from aqueous solutions by AC_Fe3O4 nano-composite: Kinetics and equilibrium studies

Background and purpose: Phenol and its derivatives are used as raw material in many chemical, pharmaceutical and petrochemical industries. It is classified as priority pollutant, due to its high toxicity. In this study, the magnetic activated carbon nano-composite was used for quick removal of phenol. Materials and methods: The activated carbon was modified by magnetic nano-particles. Then physical properties of the adsorbent were investigated using BET, XRD and SEM. Afterwards, adsorption behavior of phenol onto the adsorbent was studied considering various parameters such as: pH, phenol concentration, contact time and adsorbent dosage. Also, the isotherms and adsorption kinetics model was studied. Results: BET analysis showed 10.25% decrease in the specific area of activated carbon after being amended by the Fe3O4 nano-particles. SEM and XRD confirmed the presence of Fe3O4 nanoparticles on the activated carbon. Optimum absorption points in this process were pH=8, contact time of 15 min and adsorbent dose 2 g/L. The Longmuir isotherm and pseudo-second-order kinetics were fitted to the data. The maximum adsorption capacity of phenol on AC_Fe3O4 was 84.033 mg/g. Conclusion: Creating magnetic properties on the activated carbon which has a high adsorption capacity of phenol could result in quick separation of phenol from aqueous solutions. Also, this adsorbent could be widely applied since it is inexpensive and simple to use. © 2015, Mazandaran University of Medical Sciences. All rights reserved

Electrochemical Process for Diazinon Removal from Aqueous Media: Design of Experiments, Optimization, and DLLME-GC-FID Method for Diazinon Determination

In the present study, electrochemical process was studied via removal of diazinon (O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate) as an insecticide/ acaricide organic case study. Influences of three operational parameters including initial ferrous ion concentration, initial hydrogen peroxide concentration, and initial diazinon concentration were measured and optimized in diazinon removal process. Response surface methodology (RSM) was used to design the experiments. The experimental data collected in a laboratory-scaled batch reactor equipped with four graphite bar electrodes as cathode and an aluminum sheet electrode as an anode. Quantitative analysis of diazinon was done with gas chromatography equipped with flame photometric detector. Disperse liquid–liquid microextraction was used prior to gas chromatography in order to extraction and preconcentration of diazinon from aqueous media to extraction phase. Acetone and chlorobenzene were used as disperser and extraction solvent, respectively. Maximum diazinon removal efficiency of 87% (0.85mg mass removal) in C0 of 2mg/L and 80% (120mg mass removal) in C0 of 300mg/L was achieved under different experimental conditions. The obtained experimental data were used for model building by RSM approach. Finally, optimization process was carried out using RSM algorithm. © 2015, King Fahd University of Petroleum & Minerals

Catalytic Ozonation of Phenolic Wastewater: Identification and Toxicity of Intermediates

A new strategy in catalytic ozonation removal method for degradation and detoxification of phenol from industrial wastewater was investigated. Magnetic carbon nanocomposite, as a novel catalyst, was synthesized and then used in the catalytic ozonation process (COP) and the effects of operational conditions such as initial pH, reaction time, and initial concentration of phenol on the degradation efficiency and the toxicity assay have been investigated. The results showed that the highest catalytic potential was achieved at optimal neutral pH and the removal efficiency of phenol and COD is 98.5% and 69.8%, respectively. First-order modeling demonstrated that the reactions were dependent on the initial concentration of phenol, with kinetic constants varying from 0.038 min−1 ([phenol]o = 1500mg/L) to 1.273 min−1 ([phenol]o = 50mg/L). Bioassay analysis showed that phenol was highly toxic to Daphnia magna (LC50 96 h = 5.6mg/L). Comparison of toxicity units (TU) of row wastewater (36.01) and the treated effluent showed that TU value, after slightly increasing in the first steps of ozonation for construction of more toxic intermediates, severely reduced at the end of reaction (2.23).Thus, COP was able to effectively remove the toxicity of intermediates which were formed during the chemical oxidation of phenolic wastewaters

Evaluation of rapid purification of high concentrations of 2, 4-Dinitrophenol in wastewater using catalytic ozonation with carboneus nanocomposite

Background and purpose: 2, 4-dinitrophenol (DNP) are carcinogenic and non-biodegradable pollutants that exist at high concentration in wastewater of chemical industries. In this study, treatment and removal of organic materials (COD) in wastewater was carried out by catalytic ozonation process (COP) using carbon Nano-composite catalysts. Materials and methods: This study was conducted in cylindrical 250 mL semi-continuous reactor and the effects of several parameters including pH of the solution (4-10), the amount of catalyst concentrations (0 to 4 g/L), reaction time (0 to 60 min), and saturated catalyst was studied on treatment of high concentration of DNP and the COD removal efficiency. Also, the kinetics were compared with single ozonation (SOP). Results: Removal efficiency of high concentrations of DNP (1500 mg/L) and kinetics of the COP process catalyst concentration of 4 g/L was 83 (0.0241 min-1) while the results in SOP were 50 (0.0108 min-1). The optimum pH was 6 with the reaction time of 60 min. However, the removal efficiency of COD at initial concentration of 610 mg/L in the SOP process was 61 which increased to 92 after addition of the catalyst. The main mechanism of process was chemical oxidation and a small share (3) was due to adsorption. Conclusion: The results showed that COP and this new catalyst effectively and quickly removed high concentrations of DNP and COD. This method is believed to be economic due to the short time of ozonation, recovery and reuse of the catalyst. © 2016, AMazandaran University of Medical Sciences. All rights reserved

Adsorption of 2, 4 dinitrophenol from aqueous solutions using ordered mesoporous carbon CMK-3

Background and purpose: 2, 4 dinitrophenol is the most important nitrophenol compound that is widely used in paints, adhesives, wood preservatives, solvents, pesticides, and explosive materials. Because of the high toxicity and non-biodegradability of 2, 4 DNP, must be prevented from entering the water body. The aim of this study was to evaluate the performance of ordered mesoporous carbon CMK-3 in adsorption of 2, 4 dinitrophenol from aqueous solutions and the effect of various parameters on the performance of this process. Materials and methods: In this experimental study, mesoporous carbon, CMK-3 was prepared using hexagonal SBA-15 mesoporous silica in a batch reactor. The synthesized materials were characterized by XRD, BET and TEM. After Synthesis of CMK-3, the effect of different parameters were investigated on adsorption process including pH (3-11), contact time (20 -180 min) initial concentration of 2, 4 dinitrophenol (10-500mg/L), and adsorbent dose (0.2-1.2 gr/L). Results: Removal efficiency increased when pH and initial concentration of 2, 4-dinitrophenol decreased and contact time and adsorbant doze increased. The optimum pH was 5 and the equilibrium time was 100 minutes. The optimal dose of CMK-3 was 0.4 g/L and the adsorption capacity of 2, 4 dinitrophenol by CMK-3 was 194 mg/g. Conclusion: In general, mesoporous carbon CMK-3 showed high capacity in removal of 2,4 dinitrophenol from aqueous solutions. Therefore, it can be used in the treatment of wastewater containing 2,4 dinitrophenol. © 2016, Mazandaran University of Medical Sciences. All rights reserved

Rapid removal of phenol from aqueous solutions by ACFe<inf>3</inf>O<inf>4</inf> nano-composite: Kinetics and equilibrium studies

Background and purpose: Phenol and its derivatives are used as raw material in many chemical, pharmaceutical and petrochemical industries. It is classified as priority pollutant, due to its high toxicity. In this study, the magnetic activated carbon nano-composite was used for quick removal of phenol. Materials and methods: The activated carbon was modified by magnetic nano-particles. Then physical properties of the adsorbent were investigated using BET, XRD and SEM. Afterwards, adsorption behavior of phenol onto the adsorbent was studied considering various parameters such as: pH, phenol concentration, contact time and adsorbent dosage. Also, the isotherms and adsorption kinetics model was studied. Results: BET analysis showed 10.25 decrease in the specific area of activated carbon after being amended by the Fe3O4 nano-particles. SEM and XRD confirmed the presence of Fe3O4 nanoparticles on the activated carbon. Optimum absorption points in this process were pH=8, contact time of 15 min and adsorbent dose 2 g/L. The Longmuir isotherm and pseudo-second-order kinetics were fitted to the data. The maximum adsorption capacity of phenol on ACFe3O4 was 84.033 mg/g. Conclusion: Creating magnetic properties on the activated carbon which has a high adsorption capacity of phenol could result in quick separation of phenol from aqueous solutions. Also, this adsorbent could be widely applied since it is inexpensive and simple to use. © 2015, Mazandaran University of Medical Sciences. All rights reserved

Disinfection of effluent using catalytic ozonation process and economical comparison with chlorination

Background and purpose: Many conventional disinfection methods of effluents raise some health, efficiency and economic concerns. In order to increase the efficiency of disinfection of real effluent, in this study, the catalytic ozonation process was performed and economically compared with chlorination. Materials and methods: Magnetic activated carbon was used as acatalyst in a semi-continuous reactor for disinfection of effluent of municipal wastewater treatment plant in Bandargaz, Iran in 2015. The efficiency of disinfection was determined by thermo-tolerant coliform as indication, and the effect of parameters such as catalyst concentration (0, 0.5, 1, 2, and 5 g/L), initial number of coliforms, contact time (1, 2, 5, 10, 20 and 40 min) and catalyst reuse on disinfection process was evaluated. Finally economic comparison was done with the chlorination. Results: The results showed that the efficiency of disinfection was increased by increase in the concentration of carbon nano-composite and contact time; at 1 g/L concentration of Catalyst about 1.99 log reduction was observed after 2 min exposure time in which the effluent standards were obtained; while 1.91 log reduction of micro-organisms was measured for single ozonation. The first-order kinetics constant of single ozonation (0.42 min-1) showed an approximately 9-fold increase when the catalyst (2 g/L) was added to the solution. After 7 times reuse of nano-composite, the diminution of efficiency was negligible (1.5); and more than 57 fall of the cost was observed in a 5-year operational period compared with chlorination. Conclusion: The catalytic ozonation with the new catalyst of effluent could effectively disinfect the effluent in a short-contact-time, and due to economic considerations it can be used as an effective and economical method in wastewater treatment plants. © 2016, Mazandaran University of Medical Sciences. All rights reserved

Removal efficiency of nitrate, phosphate, fecal and total coliforms by horizontal subsurface flow-constructed wetland from domestic wastewater

Background: Constructed wetlands are systems designed based on the utilization of natural processes, including vegetation, soil, and their associated microbial assemblage to assist in treating different types of wastewater. Methods: Two local Appalachian plants (Louis latifolia and Phragmites australis) were planted into smallscale constructed wetlands to treat domestic wastewater in the North of Iran. The influent wastewater and the effluent from each wetland were sampled daily for 120 days. Experiments were conducted based on the mean ± standard deviation (SD) by analysis of variance (ANOVA). Results: It was found that nitrate, phosphate, fecal and total coliforms were reduced by 84.4%, 94.4%, 96.3%, 93.9% for P. australis and 73.3%, 64.0%, 94.4%, 92.1% for L. latifolia, respectively. Conclusion: According to the results, by using the HF-CW technology with L. latifolia and P. australis plants, the treated wastewater fully meets the wastewater discharge parameters of WHO standards

Influence of bioaugmentation on biodegradation of phenanthrene-contaminated soil by earthworm in lab scale

Background: Use of earthworm to eliminate the phenanthrene from the soil (bioaccumulation) is developed as an economical method. Bioaugmentation of microorganism was used for promotion of bioaccumulation by earthworm. The aim of this study was to determine the bioaccumulation or biodegradation of phenanthrene by Eisenia fetida and bacterial consortium in polluted soil. Methods: The amount of 0.4 kg of the polluted soil in the ratio of 10 and 30 mg phenanthrene per kg of dry soil was transferred into each pot. Afterwards, bacteria and earthworms were added to each pot in separate and combination. The samples were kept under field conditions, and the retention concentrations of phenanthrene were analyzed after 8 weeks. Results: Results showed that the Eisenia fetida was able to significantly remove phenanthrene from the polluted soil samples. Bioaccumulation and bioaugmentation alone have the removal efficiency of 60.24 and 50.3, respectively. In the combined mode, phenanthrene removal efficiency was 63.81. Conclusions: The current study indicated that the use of earthworms, could improve both phenanthrene bioavailability and microbial activity, which led to enhancing removal of carbon-based pollutants. ©2014 Asgharnia et al