ABSTRACT
In this work, a novel adsorbent with stabilizing of PAMAM dendrimer on the surface of sand was successfully synthesized and used to remove NP from water. The characterization of the adsorbent was performed by XRD, FTIR, TEM, and FE-SEM. Batch and column studies were conducted to evaluate the performance of the adsorbent. It was found that Freundlich isotherm and pseudo-second order models are perfectly stimulated the adsorption behavior and kinetic rate of NP uptake. In column study, first the effect of bed depth, flow rate and initial concentration of NP on the performance of the adsorbent were evaluated then the breakthrough curve for each condition was drawn. Finally, Thomas model constants to describe NP adsorption were calculated. As the result of the experiments, it might be concluded that in conventional water treatment plants which the removal of NP is negligible, the use of synthesized adsorbent as a filter media can be a promising way to selectively remove NP from water.
ABSTRACT
This work makes a comparison between electrocoagulation (EC), photoelectrocoagulation, peroxi-electrocoagulation and peroxi-photoelectrocoagulation processes to investigate the removal of chemical oxygen demand (COD) from pharmaceutical wastewater. The effects of operational parameters such as initial pH, current density, applied voltage, amount of hydrogen peroxide and electrolysis time on COD removal efficiency were investigated and the optimum operating range for each of these operating variables was experimentally determined. In electrocoagulation process, the optimum values of pH and voltage were determined to be 7 and 40 V, respectively. Desired pH and hydrogen peroxide concentration in the Fenton-based processes were found to be 3 and 300 mg/L, respectively. The amounts of COD, pH, electrical conductivity, temperature and total dissolved solids (TDS) were on-line monitored. Results indicated that under the optimum operating range for each process, the COD removal efficiency was in order of peroxi-electrocoagulation > peroxi-photoelectrocoagulation > photoelectrocoagulation>electrocoagulation. Finally, a kinetic study was carried out using the linear pseudo-second-order model and results showed that the pseudo-second-order equation provided the best correlation for the COD removal rate.
Subject(s)
Drug Industry , Electrocoagulation/methods , Industrial Waste , Oxygen/chemistry , Water Pollutants, Chemical/isolation & purification , Hydrogen-Ion Concentration , Kinetics , Photochemical ProcessesABSTRACT
Electrocoagulation (EC) process using aluminum electrodes is proposed for removing fluoride from treated industrial wastewater originated from steel industry. Effects of different operating conditions such as temperature, pH, voltage, hydraulic retention time (HRT) and number of aluminum plates between anode and cathode plates on removal efficiency are investigated. Experimental results showed that by increasing HRT, removal efficiency increases but after 5 min changes are negligible. Therefore, the total HRT required is only 5 min. The more HRT, the more electrical current is needed in order to achieve to constant voltage and temperature in system. In addition, it is found that pH value decreases from 6.91 to 4.6 during first 10 min but it increases up to 9.5 during 50 min. After treatment, the fluoride concentration was reduced from initial 4.0-6.0 mg/L to lower than 0.5 mg/L. The pH of the influent is found as a very important variable which affects fluoride removal significantly. The optimal range for the influent is 6.0-7.0 at which not only effective defluoridation can be achieved, but also no pH readjustment is needed after treatment. Moreover, increasing number of aluminum plates between anode and cathode plates in bipolar system does not significantly affect fluoride removal. Finally, the kinetic analysis is done for the system which indicates that the adsorption system obeys the second-order kinetic model.
