Özge Hanay

Effect of anions on removing Cu2+, Mn2+ and Zn2+ in electrocoagulation process using aluminum electrodes

In the present study, the performance of electrocoagulation process with aluminum electrodes in the treatment of Cu(2+), Zn(2+) and Mn(2+) containing aqueous solutions was investigated by depending on type of anion in solution, considering some operating conditions such as initial metal concentration and pH. Results obtained from synthetic wastewater showed that type of anion in solutions has a significant effect on the metal removal. The initial concentration of zinc influenced significantly the performance of electrocoagulation process as compared with the results obtained from Mn and Cu metals. Anions studied did not generate an important difference between pH variations. Best removals for three metals were achieved with increasing the pH in the presence of both anions. Total removals of copper and zinc reached almost 100% after 5 min at pH values > 7. At the end of the experiments for 35 min, the Mn removals were 85 and 80% in the presence of sulfate and chloride anions, respectively.

Evaluation for Agricultural Usage with Speciation of Heavy Metals in a Municipal Sewage Sludge

This study was carried out to evaluate the agricultural usage of an anaerobically digested sludge in the contents and fractions of heavy metals. Therefore, a sequential extraction scheme according to the BCR’s (Community Bureau of Reference) guidelines and total acid digestion were applied to sewage sludge samples. The results of total heavy metal concentrations in sewage sludge showed that the highest total concentrations were Fe, Zn and Mn. When Turkish, Europe and US EPA directives were compared with each other by depending on the use of sludge for agricultural purposes, all the heavy metals determined for this sludge were below the maximum permitted levels, except for Cd. This sludge should not be applied to land due to its high Cd content. The results of heavy metal fractions indicated that some metals (Cd, Mn, Pb, and Fe) distributed mainly in the residual fraction. All fractions of Zn showed no variation. Cu and Cr were most abundant in the oxidizable phase while Ni was in exchangeable phase. Although total content of Ni in the sludge is lower than the maximum levels allowed by all the directives, it tends to be easily moved and dispersed in the environment. Due to its high mobility, the examined sewage sludge may cause phyto-toxicity after its agricultural application.

Effect of EDTA as washing solution on removing of heavy metals from sewage sludge by electrokinetic

This paper presents the effect of ethylene diamine tetraacetic acid (EDTA) as a washing solution on the electrokinetic process for removal of Cr, Pb and Zn from sewage sludge. The sequential chemical extraction scheme according to the guidelines of BCR (Community Bureau of Reference) was applied to the sludge samples to evaluate the effect of EDTA on metal fractionation during electrokinetic processes. The highest removals of the heavy metals were 34% for Cr, 27% for Pb and 20% for Zn with 0.1N EDTA. The removal priority of the metals by electrokinetic process was found to be Cr>Pb>Zn. According to the results of BCR analysis, addition of EDTA did not create the inter-transformation of Cr, Pb and Zn although the metal concentration decreased.

Removal of Pb from sewage sludge by electrokinetics: Effect of pH and washing solution type

In this study, the effect of pH and washing solution on the removal of lead from sewage sludge by electrokinetics was investigated. The six experimental runs were carried out at two different pH values – 3 and 4 – using acetic acid, nitric acid and phosphoric acid. In addition, the sequential chemical extraction scheme according to the BCR’s (Community Bureau of Reference) guidelines was applied to the sludge samples to evaluate the effect of acidic solutions on Pb fractionation during electrokinetic processes. Using nitric acid as the washing solution resulted in the highest removal efficiency of Pb (39%) amongst all the experiments. Acetic acid also provided similar removal percentages (37% and 38%) at different pre‐acidification conditions. On the other hand, the removal efficiencies were 36% and 27% with pre‐acidification using phosphoric acid at pH 3 and 4, respectively, resulting in the lowest efficiencies. The results obtained by BCR analysis showed that the metal present near the anode partitioned in to more mobile forms while the metal near the cathode partitioned in to less mobile forms, such as precipitated or adsorbed forms, as the electrokinetic process proceeded. The inter‐fractional transformations of Pb formed only when using acetic acid. The similar percentages obtained by using different washing solutions indicated that the type of acid used as washing solution was less effective than the values of pH for removal of Pb from sewage sludge during the electrokinetic process.

Membrane fouling control in anaerobic submerged membrane bioreactor

AbstractIn this study, the aim was to assess the impact of different membrane modules such as cylinder-shaped, funnel-shaped, and U-shaped on the membrane fouling behavior in a laboratory-scale submerged anaerobic membrane bioreactor (AnSMBR) treating the synthetic wastewater for over 124 days. A series of analysis, including soluble microbial products (SMP), extracellular polymeric substances (EPSs), scanning electron microscopy, energy dispersive X-ray spectroscopy, particle size distribution, and filtration resistances, was performed by considering all membrane modules. The results showed that difference between COD and TOC removals was negligible in membrane modules designed at different forms. However, the priority of the membrane modules in terms of providing high permeate fluxes was found to be cylinder-shaped > funnel-shaped > U-shaped bundle. Both SMP and EPS within cake formed on the fibers in the cylinder-shaped module were lower than those in the U-shaped and funnel-shaped modules. The particl...

Comprehensive evaluation of adsorption and degradation of tetracycline and oxytetracycline by nanoscale zero-valent iron

AbstractThe interaction of tetracycline (TC) and oxytetracycline (OTC) with nanoscale zero-valent iron (nZVI) was examined with a batch experimental series in order to determine the removal efficiency and transformation products. Experimental variables, such as solution pH, nZVI dosage, contact time, initial TCs concentration, and reaction temperature, were systematically studied. Adsorption kinetics showed that equilibrium was reached within 2 h according to the pseudo-second-order model. The adsorption behavior was pH-dependent and favored at pH 6 regardless of TC type considered due to electrostatic attraction between nZVI and TCs. The adsorption capacity of TC was more than that of OTC. The results of LC-MS-MS showed that main transformation product was 4-epi-tetracycline for TC and insignificant for OTC. On the other hand, desorption studies exhibited that nZVI adsorbed not only parent compounds but also transformation products. The results showed that the removal mechanism of TC and OTC by using nZV...

Removal of tetracyclines from aqueous solution by nanoscale Cu/Fe bimetallic particle

ABSTRACTBimetallic nanoparticle (BNP) that comprises nanoscale zero-valent iron with a noble metal such as Pd, Pt, Ni, Ag, or Cu has been effective in removing various organic and inorganic compounds. In this study, the removal performance of tetracycline antibiotics, tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC), from aqueous solution by nanoscale copper/iron (Cu/Fe) bimetallic particle was investigated. Batch experiments were performed to evaluate the effect of experimental variables such as solution pH, bimetallic particle dosage, and temperature on the removal efficiency of tetracyclines. The results obtained from the study indicated that the removal rate of tetracyclines was greatly dependent on pH. The removal of TCs above 90% was achieved at optimum conditions. The Langmuir and Freundlich adsorption models were applied to experimental data and the results fitted to Langmuir model. The pseudo-first-order and the pseudo-second-order models were used to express of adsorption ki...