Nasser S. Awwad

Sorption of lanthanum and erbium from aqueous solution by activated carbon prepared from rice husk.

A biomass agricultural waste material, rice husk (RH) was used for preparation of activated carbon by chemical activation using phosphoric acid. The effect of various factors, e.g. time, pH, initial concentration and temperature of carbon on the adsorption capacity of lanthanum and erbium was quantitatively determined. It was found that the monolayer capacity is 175.4 mg g(-1) for La(III) and 250 mg g(-1) for Er(III). The calculated activation energy of La(III) adsorption on the activated carbon derived from rice husk was equal to 5.84 kJ/mol while it was 3.6 kJ/mol for Er(III), which confirm that the reaction is mainly particle-diffusion-controlled. The kinetics of sorption was described by a model of a pseudo-second-order. External diffusion and intra-particular diffusion were examined. The experimental data show that the external diffusion and intra-particular diffusion are significant in the determination of the sorption rate. Therefore, the developed sorbent is considered as a better replacement technology for removal of La(III) and Er(III) ions from aqueous solution due to its low-cost and good efficiency, fast kinetics, as well as easy to handle and thus no or small amount of secondary sludge is obtained in this application.

Factors Affecting on the Sorption/Desorption of Eu (III) using Activated Carbon

Abstract The sorption and desorption of Eu (III) on H‐APC activated carbon using a batch technique has been studied as a function of carbon type, shaking time, initial pH solution, temperature, particle size of carbon, and concentration of the adsorbent and the adsorbate. The influence of different anions and cations on adsorption has been examined. The experimental data have been analyzed by Langmuir, Freundlich, and Temkin sorption isotherm models and the adsorption data for Eu (III) onto activated carbon were better correlated to the Temkin isotherm and the maximum absorption capacities obtained was 46.5 mg g−1. Anions of phosphate, carbonate, oxalate, and acetate were found to increase the adsorption of Eu (III), whereas nitrate, chloride and all studied cations, potassium, sodium, calcium, magnesium, and aluminum have a negative effect on the adsorption capacity. More than 99% europium adsorbed on H‐APC eluted with 0.5 M HCl solution. The activated carbon prepared from apricot stone using 70% H3PO4 could be considered as an adsorbent that has a commercial potential for Eu (III) treatment.

Removal of synthetic reactive dyes from textile wastewater by Sorel's cement

Removal of some reactive dyes (RY-145, RR-194 and RB-B) from textile wastewater effluents using Sorels cement is described. Parameters affecting dye uptake including contact time, reagent dosage and pH are examined and optimized. Dye adsorption equilibrium data are fitted well to the Langmiur isotherm rather than Freundlish isotherm. The adsorption isotherm indicates that the adsorption capacities are 107.67, 120.89 and 103.14 mg dye per gram of Sorels cement for RY-145, RR-194 and RB-B reactive dyes, respectively. The adsorption isotherms, including Langmuir constant (Q degrees and b) and Frendlich constant (K(F) and n), for the dyes decrease with the increase of temperature. The values of enthalpy change (DeltaH) for RY-145, RR-194 and RB-B dyes are -146.96, -49.23 and -264.86 kJ mol(-1), respectively, indicating that the removal process is exothermic. The sorption of the dyes is enhanced by increasing the pH, reaching a maximum at pH 6-11. Experimental runs conducted to measure the chemical oxygen demand (COD) of textile wastewater loaded with reactive dyes, reveal approximately 96% removal of the COD contents within 30 min under optimized conditions.

Purification of wet phosphoric acid from ferric ions using modified rice husk

Abstract A new method has been developed to reduce the concentration of Ferric ions present as inorganic impurities in crude Egyptian phosphoric acid. This method is based on the silica extracted by alkaline treatment of rice husk to carry out the exchange of ions. Several parameters (contact time, temperature, sorbent type, sorbent mass, and batch factor) were examined. Simultaneous determination of Fe 3+ ions in presence of uranium ions before and after treatment revealed that the concentration of uranium was reduced by ∼18% during the removal of Fe 3+ . Adsorption isotherm indicates that the monolayer coverage is 0.386 g Fe 3+ ions per g sorbent. In dynamic mode, the adsorption capacity at ( C e / C o =50% or Q 0.5 ) was=22.5 mg/g and the column recycled at least three times and only needs 150 ml of 0.1 M HNO 3 for each regeneration and no weight loss in sorbent per cycle should be considered. Therefore, the developed rice husk adsorbent is considered as a better replacement technology for removal of Fe 3+ ions due to its low cost and good efficiency in this application. The cost of 1 kg of the modified rice husk (MRH) is estimated and the sorption mechanism is discussed.

Treatment of phosphogypsum waste produced from phosphate ore processing.

Phosphogypsum (PG), primary byproduct from phosphoric acid production, is accumulated in large stockpiles and occupies vast areas of land. Phosphogypsum is a technologically enhanced naturally occurring radioactive material (TE-NORM) that contains radionuclides from (238)U and (232)Th decay series which are of most radio-toxicity. The reduction in concentration of radionuclides content from PG was based on leaching of (226)Ra, (210)Pb, (238)U and (40)K using tri-butyl phosphate (TBP) and tri-octyl phosphine oxide (TOPO) in kerosene. The factors which affect the leaching process such as contact time, concentration of the solvent and temperature were optimized. Based on the experimental results, about 92.1, 88.9, 83.4, 94.6% of (226)Ra, (210)Pb, (238)U and (40)K respectively were successfully removed from the PG. The reduction in the concentration of radionuclides was accompanied by reduction in the concentration of rare earth elements (∑REE) equals to 80.1%. Using the desired organic extractant under optimum conditions for treatment of the PG waste leads to obtain a decontaminated product that can be safely used in many industrial applications.

Sorption of Np(V) by synthetic hydroxyapatite

Abstract The sorption of Np(V) to synthetic hydroxyapatite was determined in batch experiments in a 0.1M NaClO4 solution. The hydroxyapatite used was of high purity as determined by SEM, EDS, XRD, FT-IR and ICP-MS analysis. Results from kinetic experiments with an initial Np(V) concentration of 1×10-7 to 1×10-6M indicate the sorption process is relatively fast with more than 90 of the Np(V) being sorbed in approximately 3 hours. Equilibrium experiments performed over the pH range of 6 to 11 indicated sorption is strongly pH dependent with distribution coefficients, Kd values (mL/g), increasing from 123L/mole at pH 6 to 69200L/mole at pH 8.5. Kd values are observed to decrease as pH further increases. Data points over a range of Np(V) concentrations were collected at pH 8 and fitted to the Langmuir isotherm model for simple adsorption. The Langmuir equation gave an excellent representation of the data. Langmuir parameters were determined to be Ca=0.032mole/mole and K=1.22×106L/mole, indicating the high affinity of hydroxyapatite for Np(V) adsorption.

Treatment of phosphogypsum waste using suitable organic extractants

Phosphogypsum (PG) is a residue of the phosphate fertilizer industry that has relatively high concentrations of harmful radioactive materials. The reduction in concentration of the radionuclides from PG was investigated. The removal process is based on leaching of radionuclides using suitable organic extractants. The studied radionuclides were 226Ra, 210Pb, 238U and 40K. The factors affect the leaching process such as type of leaching materials, contact time, concentration of the desired solvent, liquid to solid ratio, and temperature were studied. Based on the experimental results, about 71.1, 76.4, 62.4, and 75.7% of 226Ra, 210Pb, 238U and 40K respectively were successfully removed from the PG. The reduction in the concentration of radionuclides was accompanied by reduction in the concentration of rare earth elements (∑REE) equals to 69.8%. Using the desired organic extractant under optimum conditions for treatment of the PG waste leads to obtain a decontaminated product that can be safely used in many industrial applications.

Comparative study on the radioactivity of TE-NORM in different components of oil separator tanks

Abstract Natural radioactivity in the crude oil, produced water, sludge and scale wastes from the petroleum industry on the Suez gulf (Abu Redeis), Egypt were investigated. A low radioactivity was found in the produced water and crude oil samples. In the sludge waste samples, the levels of radioactivity were found to be 11.96 and 1.75 kBq kg−1 for Ra-226 (of U-series) and Ra-228 (of Th-series), respectively. In the scale waste samples, the levels of radioactivity were 11.7 and 4.2 kBq kg−1 for Ra-226 and Ra-228, respectively. Leaching of different radionuclides in the sludge and scale wastes was investigated using mineral acid alone or after treatment with certain carbonate solutions. The different parameters affecting the treatment were optimized. It is found that high removal of Ra-226 was achieved from sludge and scale wastes when pretreated with 10% sodium carbonate solution, followed by acid dissolution. Removal % of Ra-226 reached 77 and 87% from the sludge and scale wastes, respectively.