Munther Kandah

Zinc and cadmium adsorption on low-grade phosphate

An attempt was made to utilize low-grade phosphate (LGP) as an adsorbent for Zn2+ and Cd2+ over a range of initial metal ions concentrations (10–50 ppm), agitation time (5–210 min), adsorbent concentration (1–7 g/l) and pH (2–6). Adsorption of both Zn2+ and Cd2+ increased with increased LGP concentration and reached maximum uptake at 5 g/l and pH between 4 and 6 for both metal ions. The amount adsorbed increases with time and initial metal concentrations for both metal ions. The equilibrium time was achieved for both metal ions after 30 min. The process of uptake obeys both the Langmuir and Freundlich isotherms. The affinity of LGP for H+ is considerably higher than for Zn2+ and Cd2+. The equilibrium uptake of zinc ions decreases with the increase in the initial cadmium ions concentration and that of cadmium ions decreases as the initial zinc ions concentration increases. Desorption of LGP with 0.1 N H2SO4 was done for three cycles successfully.

Nickel Removal from Aqueous Solutions Using Sheep Manure Wastes

This paper reports a study on the potential use of sheep manure waste (SMW) for the removal of nickel ions from aqueous solutions. The adsorption of nickel ions from aqueous solutions on SMW has been studied as functions of contact time, initial pH, amount of sorbent, sorbent particle size, initial concentration of nickel ions, salt, and chelating agents. The experimental results showed that the SMW has a high affinity for nickel binding, where 79 % removal of 100 ppm initial nickel ions concentration was obtained using 8.0 mg SMW/mL, at pH 6.5 in 4 minutes equilibrium time. The equilibrium adsorption data were analyzed using four different isotherms: the Langmuir, Freundlich, Redlich‐Peterson, and Sips isotherm equations. The results of the kinetic studies showed that the adsorption of nickel ions on SMW is a pseudo‐first order with respect to the nickel ions solution concentration.

Competitive Adsorption of Nickel and Cadmium on Sheep Manure Wastes: Experimental and Prediction Studies

Sheep manure wastes (SMW) previously have been shown to be very efficient in removing nickel and cadmium from single-component, dilute aqueous solutions. Simultaneous removal of nickel and cadmium ions from aqueous solutions using SMW has been investigated in this study. The experimental results showed that the SMW has a relatively higher affinity for cadmium binding than that for nickel. Different multicomponent-isotherm models; extended Langmuir, modified Langmuir, extended Redlich–Peterson, and extended Sips isotherm models, were used to predict the removal of either ions using single metal isotherm data.

Study of microdroplet generation from vacuum arcs on graphite cathodes

The emission of microdroplets from the cathode surface in the vacuum arc ion plating deposition technique is the major drawback to the technique’s industrial use. The generation of these particles from graphite cathodes is studied in this article and correlated to the local thermal load in the cathode spot area. A pulse discharge was used for a precise control of this load. Increases in the arc current level, arc duration time, and, more generally, the local temperature of the cathode were found to increase the number and the average size of the emitted particles. Particles under these conditions also show an increase in the width of their size distributions. Increasing the distance between cathode and substrate was found to decrease the number density of particles observed on the substrate according to the solid angle covered. The microdroplets show a graphite structure and diameters between 0.2 and 2.0 μm. Conditions needed to decrease the number of particles emitted to the substrate are given.

Erosion study on graphite cathodes using pulsed vacuum arcs

In this work, the dependence of the cathode erosion rate on vacuum arc spot velocities and cathode pore size are investigated for four types of graphite under an external variable magnetic field. Different graphite cathode properties show varying erosion rates, indicating that each graphite type should be treated as a different material. Increasing the spot velocity through an increase of the magnetic field intensity on a given cathode material decreases the erosion rate. At given magnetic field values, cathodes having higher arc velocities show an increase in the erosion rate. Other studies indicating that the increase in the arc spot velocity leads to a reduction in macroparticles emission indicate a possibility of increasing. The emission of the carbon ions component. A decrease in the pore size of the cathode also shows an increase in the cathode erosion rate.

The Aqueous Adsorption of Copper and Cadmium Ions onto Sheep Manure

Dried sheep manure (SM) has been found to be an effective adsorbent for the removal of copper and cadmium ions from dilute aqueous solutions. Batch adsorption experiments using different concentrations of copper and cadmium ions (2.0–20.0 mg/ml) were carried out for different periods of agitation. Adsorption uptakes were found to increase with an increase in the initial metal ion concentration, SM concentration and solution pH for both copper and cadmium ions. Maximum uptakes for 100 ppm Cu2+ and 100 ppm Cd2+ ions were found to be 17.8 mg/g and 10.8 mg/g, respectively. The equilibrium uptakes for both copper and cadmium ions were attained within the first 10 min. The Langmuir isotherm model failed to represent the adsorption of both copper and cadmium ions on SM. In contrast, the Freundlich isotherm model fitted the experimental data for both copper and cadmium ions very well. The presence of EDTA in the solution decreased the equilibrium uptake of both copper and cadmium ions significantly.

Competitive Adsorption of Copper-Nickel and Copper-Cadmium Binaries on SMW

In this study, the technical feasibility of using a low‐cost sorbent, sheep manure waste (SMW), for the removal of copper, nickel and cadmium ions from aqueous solutions containing Cu2+ ‐‐Cd2+ or Cu2+ ‐‐Ni2+ binaries is investigated. The scope of the study includes the investigation of the affinity of each metal ion in the presence of the other. Experimental results showed that the SMW has high affinity for the three studied heavy metals, and the affinity of the SMW for these metals is in the order copper > cadmium > nickel. The presence of copper in a solution containing Ni2+ or Cd2+ reduces significantly the percentage removal of both nickel and cadmium. On the other hand, the percentage removal of copper was not affected significantly by the presence of either nickel or cadmium. The equilibrium adsorption data were fit very well with Langmuir, Freundlich, Redlich‐Peterson, and Sips isotherm equations. The prediction of the binary adsorption from single metal adsorption data was in fair agreement with the experimental results. The role of ion exchange and carboxyl groups in the adsorption process were also studied.

The Potential Use of Low-Grade Phosphate Rocks as Adsorbent

This study evaluates the suitability of using low-grade phosphate for Cu 2+ removal. The study also investigates the effects of the presence of ethylenediaminetetraacetic acid (EDTA), citric acid, tartaric acid and sodium chloride in a solution containing Cu 2+ on the adsorption capacity of Cu 2+ onto low-grade phosphate. For aqueous solutions with 100 ppm Cu 2+ , the percentage removal of Cu 2+ at pH 4 onto 0.2 g of 0.063 mm low-grade phosphate was found to be 96.6% after one hour. Using one mmol of either Cu 2+ , Cu-NaCl, Cu-tartaric acid, Cu-EDTA, or Cu-citric acid aqueous solutions, the present work shows trend of the percentage removal of Cu 2+ at equilibrium time: Cu 2+ > Cu-NaCl > Cu-tartaric acid > Cu-EDTA > Cu-citric acid. It is also found that increasing the concentration of ligand to copper ratio decreases the percentage removal of Cu 2+ significantly. This means that the adsorption capacity is ligand type and concentration dependent.

Vacuum arc cathode spot movement on various kinds of graphite cathodes

Vacuum arc spot movement on various graphite cathode materials is investigated. The dependence of the arc spot velocity on physical, mechanical and electrical properties of the different cathode materials is measured in the presence of a variable magnetic field. It is shown that the cathode spot velocity is larger on cathodes having large grain size, low electrical resistivity and higher apparent density. The spot velocity is lower for cathodes having larger pore sizes and total porosity.

Evidence of columnar diamond growth structures within cathode spot craters of vacuum arcs on carbon

Cross-sections of erosion craters formed by vacuum arc discharges on graphite cathodes are examined using electron microscopy. These reveal erosion craters that are covered with a growth layer forming a continuous film on the arced surface. The film surface is composed of sphere-like structures similar to cauliflower diamond and to the emitted macro-particles (MPs) observed in coating experiments using graphite vacuum arc sources. The film thickness within the cathode erosion craters evolves with the mean values of the MP diameter and mean crater depth for four graphite material morphologies. These two parameters increase with a decrease in arc spot velocity. The growth layer shows a relatively porous columnar structure, with micro-Raman spectroscopy indicating an evolution from amorphous carbon (cathode base), to graphitic (middle), to diamond dominating the top layer.