Cafer Saka

Applications on agricultural and forest waste adsorbents for the removal of lead (II) from contaminated waters

At present, there is growing interest in using low cost, commercially available materials for the adsorption of heavy metals. The major advantages of adsorption technologies are its effectiveness in reducing the concentration of heavy metal ions to very low levels and the use of inexpensive adsorbent materials. In this review, agricultural and forest waste adsorbents were used to remove Pb2+ ions in wastewater treatment, and their technical feasibilities were reviewed in studies mainly from 2000 to 2010. They all were compared with each other by metal binding capacities, metal removal performances, sorbent dose, optimum pH, temperature, initial concentration and contact time. Although commercial activated carbon is widely used in wastewater treatment applications, it has high costs. The use of agricultural by-products as adsorbent material to purify heavy metal contaminated water has become increasingly popular through the past decade because they are less expensive, biodegradable, abundant and efficient. Instead of activated carbon, this study was focused on the inexpensive materials such as agricultural and forest waste. It was shown that these alternative adsorbents had sufficient binding capacity to remove Pb2+ ions from wastewater.

Preparation and characterization of activated carbon from acorn shell by physical activation with H2O-CO2 in two-step pretreatment.

Activated carbons have been prepared by physical activation with H2O-CO2 in two-step pre-treatment including ZnCl2-HCl from acorn shell at 850 °C. The active carbons were characterized by N2 adsorption at 77 K. Adsorption capacity was demonstrated by the iodine numbers. The surface chemical characteristics of activated carbons were determined by FTIR spectroscopic method. The microstructure of the activated carbons prepared was examined by scanning electron microscopy. The maximum BET surface area of the obtained activated carbon was found to be around 1779 m(2)/g.

Removal of Lead(II) from Aqueous Solutions using Pre-boiled and Formaldehyde-Treated Onion Skins as a New Adsorbent

The adsorption characteristics of Pb2+ on pre-boiled treated onion skins (PTOS) and formaldehyde-treated onion skins (FTOS) were evaluated. The effects of Pb2+ initial concentration, agitation rate, solution pH, and temperature on Pb2+ adsorption were investigated in batch systems. Pb2+ adsorption was found to increase with increase in initial concentration. The point of zero net charge (PZC) was 6.53. The optimum pH for the maximum removal of Pb2+ was 6.0. The adsorption equilibrium data was best represented by the Langmuir isotherm model for FTOS and the Freundlich isotherm model for PTOS. The maximum amounts of Pb2+ adsorbed (qm), as evaluated by the Langmuir isotherm, was 200 mgg−1 for FTOS. The efficiencies of PTOS and FTOS for Pb2+ removal were 84,8.0% and 93.5% at 0.15 g/200 mL−1 adsorbent dose, respectively. (C 0 = 50 mg L−1). Study concluded that onion skins, a waste material, have good potential as an adsorbent to remove toxic metals like Pb2+ from water. Boehm titration analysis was conducted to determine the surface groups. It was found that the adsorption kinetics of Pb2+ obeyed pseudo-first-order kinetic model as based on Δq (%) values. FTIR and SEM images before and after adsorption was recorded to explore changes in adsorbent-surface morphology. Activation energy (Ea) was obtained as 25.596 kJ/mol.

Removal of Methylene Blue from Aqueous Solutions by using Cold Plasma, Microwave Radiation and Formaldehyde Treated Acorn Shell

In this paper, cold plasma (CPTAS), formaldehyde (FTAS), and microwave radiation treated (MTAS) acorn shell obtained from Quercus petraea tree as biosorbent was characterized and its dye removal ability at different dye concentrations was studied. The isoelectric point, functional groups and morphology of acorn shell was investigated as adsorbent surface characteristics. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and UV–Vis spectrophotometry were used. Methylene blue (MB) was used as model cationic dye. The Langmuir and Freundlich adsorption isotherm models were applied to describe the equilibrium isotherms. The results indicated that the data for adsorption of MB onto treated acorn shell fitted well with the Langmuir isotherm model. Comparison of adsorption capacities of CPTAS with FTAS has shown a significant increase by as much as about 30 mg/g (33.32%) in MB adsorption.The pseudo-first order, pseudo-second order kinetic models were examined to evaluate the kinetic data, and the rate constants were calculated. Adsorption kinetic of dyes followed pseudo-first order kinetics. Thermodynamic parameters such as free energy, enthalpy, and entropy of dye adsorption were obtained. The results indicated that acorn shell could be used as a natural biosorbent for the removal of cationic dyes.

Hydrogen Generation from Sodium Borohydride Hydrolysis with a Cu–Co-Based Catalyst: A Kinetic Study

In the present work, Cu–Co-supported catalysts were tested for hydrogen generation from the hydrolysis reaction of an alkaline sodium borohydride solution. Cu–Co catalysts were prepared by the chemical reduction with NaBH4 and characterized with scanning electron microscope. The effect of Cu–Co ratio was investigated. The results suggested that the optimal mixture percentage of Cu–Co catalyst was 60:40; excessive Cu resulted in poor catalytic activity. The reactions were carried out at temperatures of 20, 30, 40, and 50°C. The experimental data was fitted to the nth-order kinetic models. The results indicate that the nth-order model gives a reasonable description of the hydrogen generation rate over all of the temperature range. The activation energy and pre-exponential factor of the nth-order reaction model were obtained as 42.66 kJ mol−1 and 1.21 × 104, respectively.

The Removal of Methylene Blue from Aqueous Solutions by Using Microwave Heating and Pre-boiling Treated Onion Skins as a New Adsorbent

Abstract Varying the parameters, such as dye concentration, adsorbent dose, and pH, carried out the potential feasibility of microwave heating treated and pre-boiling treated onion skins for removal of methylene blue. The amount of dye uptake (mg g−1) was found to increase with an increase in contact time, adsorbent dosage, and in initial dye concentration. Lagergren first-order and second-order were used to fit the experimental data. Equilibrium isotherms were analyzed by Langmuir and Freundlich. Based on regression coefficient, the equilibrium data found fitted well to the Langmuir equilibrium model than other models. The adsorption capacities were found to be 142.67 and 55.55 mg g−1 for microwave heating treated onion skins and pre-boiling treated onion skins by Langmuir isotherm. The equilibrium time was found to be 150 min for 50 mg L−1 dye concentrations. The maximum removals for microwave heating treated onion skins and pre-boiling treated onion skins were obtained 86.34 and 94.13% at natural pH 10.0 for adsorbent doses of 0.15 g/200 mL.

Hydrogen Production by Catalytic Hydrolysis of Sodium Borohydride with a Bimetallic Solid-State Co-Fe Complex Catalyst

The addition of the active non-noble metal species on a ligand can influence the catalytic performance of catalyst. In the present work, a new bi-metallic solid-state complex catalyst system, including 4-4’-methylene bis(2,6-diethyl) aniline-3,5-di-tert-butylsalisilaldimin ligand and Fe and Co metal salts are prepared for hydrogen generation by catalytic hydrolysis of NaBH4. It was found that the Co/Fe mixture ratio, temperature, NaBH4, and NaOH concentrations, all exert considerable influence on the catalytic effectiveness of Co–Fe complex catalyst towards the hydrolysis reaction of NaBH4. The results suggested that the optimal mixture percentage of Co–Fe complex catalyst is 80:20. The obtained complex catalysts are characterized by XRD, FT-IR, and SEM techniques.

The Effect of Microwave Irradiation on a Co-B-based Catalyst for Hydrogen Generation by Hydrolysis of NaBH4 Solution

A Co-B-based catalyst was prepared under microwave irradiation for hydrogen generation by hydrolysis of NaBH4 solution. The activity of Co-B catalyst for hydrogen generation was studied in comparison with another Co-B catalyst prepared by the known methods. The results show that Co-B catalyst reduced prepared under microwave irradiation was quick and was completed in only 17 min, while the Co-B catalyst produced in a known method was slow and was completed in 27 min. The hydrogen generation from the hydrolys of NaBH4 with Co-B catalyst was investigated depending on NaBH4 and NaOH concentrations in solution, temperature, microwave applying time, and microwave applying power. Hydrolysis kinetics of NaBH4 were investigated at a temperature range of 30–50°C and zero-order kinetics were applied to the obtained data.

High-Performance Liquid Chromatography Methods to Simultaneous Determination of Anti-Retroviral Drugs in Biological Matrices

Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS or Aids) is symptoms and infections resulting from the damage to the human immune system. The purpose of this paper is to review the literature for high performance liquid chromatography methods to simultaneous determination of anti-retroviral drugs in biological matrices covering the articles mainly from 2001 to 2009. The biological matrix samples include various biological matrices such as human plasma, serum, breast milk, saliva, cerebrospinal fluid and seminal fluid. The review covers high-performance liquid chromatography coupled with ultraviolet detection and reversed-phase high-performance liquid chromatography coupled with tandem mass spectrometry.

Effects of plasma treatment, La content and temperature on the La–Ni–Mo–B catalysts for hydrogen production from NaBH4 hydrolysis

ABSTRACT La–Ni–Mo–B catalysts with 0.15, 0.21 and 0.30-mol La molar ratio are prepared by a mixing method followed by a plasma treatment, characterised and investigated for hydrogen production via sodium borohydride hydrolysis. XRD, SEM, Brunauer–Emmett–Teller and FTIR techniques are used for characterising the catalysts. The hydrogen generation rate at 60°C compared to 30°C using La–Ni–Mo–B under the same conditions is significantly different. The effect of temperature, plasma application time and different plasma gases on hydrogen generation from NaBH4 hydrolysis reaction using La0.21–Ni–Mo–B catalyst is investigated. It was found that the plasma-treated catalysts exhibited low activation energy for zero order (58 kJ mol−1).