Sabeha Ouki - Academia.edu (original) (raw)

Papers by Sabeha Ouki

Journal of Property Investment & Finance, 2008

ABSTRACT Abstract: LG-MgO is an economically feasible and environmental friendly material compare... more ABSTRACT Abstract: LG-MgO is an economically feasible and environmental friendly material compared to ordinary Portland cement. LG-MgO is as alkaline as lime which acts as a buffering agent within the pH 9-11, helps minimizing the solubility of heavy metals and avoids the re-dissolution that lime does when used in the matrix. Bulk density, unconfined compressive strength (UCS) and setting time are measured as the physical parameters. A study of the leaching behaviour of stabilised EAFD waste has been performed using granular leaching test-BS EN 12457-3:2002. Several S/S forms were produced by using cement and MgO as binders. The results also showed that replacing cement by up to 80% of MgO reduced strength from 50.4 to 5.6 MPa at 28 days of curing age. The addition of EAFD at 40% decreased strength from 50.4 to 38.4 MPa and at 70% waste addition up to 12.4 MPa for the pure-cement-based waste forms at curing age of 28 days. Although the UCS values decreased with the addition of both EAFD and MgO into the matrix, they still met the UCS Waste Acceptance Criteria (WAC) limits (> 1MPa at UCS28days). The results proved that with 70% EAFD addition into the mix matrix both the initial and final setting times have increased compared to 0% and 40% waste addition. ZnO and PbO content of the EAFD cause the retardation of hydration reactions. The acid neutralisation capacity (ANC) has been undertaken to evaluate the worst leaching case scenario. In order to test the worst case scenario acid was added at different ratios from 1 to 16 meq/g acid additions. No heavy metals leaching were observed at both C-M-1-2 and C-M-1-4 ratios where there is no waste. Mo leached for the rest of the mix designs where even at 12 meq/g acid addition none of the metals (Pb, Cd, Cr, and Zn) leached extensively. All the metals leaching rates, except for Mo, were within the WAC limits and hence met the leaching requirements. Granular leaching test results, which are same as 0 meq/g acid addition leaching rates of mix designs, met the WAC limits. Only at C-M-1-2-70 and C-M-1-4-70 mix ratios Mo leached at concentrations exceeding the WAC limits.

Journal of Solid Waste Technology and Management

Water Science & Technology, 2006

The presence, in sewage sludge, of excess levels of the potentially toxic elements (PTE) copper, ... more The presence, in sewage sludge, of excess levels of the potentially toxic elements (PTE) copper, zinc, chromium, cadmium, nickel, lead and mercury, could impact on our ability to recycle these residues in the future. Far stricter limits on the levels of PTEs are likely in proposed legislation. A method involving the dosing of Fenton&amp;#39;s reagent, a mixture of ferrous iron and hydrogen peroxide, under acidic conditions was evaluated for its potential to reduce metal levels. The [Fe]:[H2O2] (w/w) ratio was found to give a good indication of the percentage copper and zinc elution obtainable. Sites with no iron dosing as part of wastewater treatment required extra iron to be added in order to initiate the Fenton&amp;#39;s reaction. A significant reduction, in excess of 70%, of the copper and zinc was eluted from both raw primary and activated sludge solid fractions. Cadmium and nickel could be reduced to below detection limits but elution of mercury, lead and chromium was less than 40%. The iron catalyst concentration was found to be a crucial parameter. This process has the potential to reduce the heavy metal content of the sludge and allow the recycling of sludge to continue in a sustainable manner.

Water, Air, and Soil Pollution, 2009

Soil and Sediment Contamination, 2007

Soil & Sediment Contamination, 16:233–251, 2007 Copyright © Taylor & Francis Group, LLC I... more Soil & Sediment Contamination, 16:233–251, 2007 Copyright © Taylor & Francis Group, LLC ISSN: 1532-0383 print / 1549-7887 online DOI: 10.1080/15320380601169441 ... Immobilization of Heavy Metals in Soil Using ... VISHNU PRIYA GADEPALLE,1 SABEHA K. OUKI,1 ...

Proceedings of the Water Environment Federation, 2014

Waste Management, 2002

In recent years, Backscattered Scanning Electron microscopy techniques (BSE), coupled with an ima... more In recent years, Backscattered Scanning Electron microscopy techniques (BSE), coupled with an image analysis system have been recognised as a powerful tool for quantitative analysis. This paper investigates the effect of metal additions (Ba, Cu, Ni, Zn, Cr(III), Pb and Cd) to Portland cement to produce a solidified product which meets the durability criteria quantified by the ratio of hydrated products and porosity. In addition, other indicators of the progress of cement hydration such as the bulk density and evaporable water of the solidified products were also measured. Metal concentrations of 0.1 and 1% per weight of cement at a constant water/cement ratio of 0.4 were examined. The same measurements were conducted on control samples of different water/ cement ratio. The results have shown that the control samples at different W/C ratio showed consistent trend in residual cement porosity, density and evaporable water content. It also showed that low dosage of metal nitrate additions can reduce cement hydration by up to 50% and at the same time reduce the observable porosity. Overall, this work has shown that Scanning Electron Microscopy (SEM) and image analysis are powerful tools and could be used to quantify the observable porosity and cement hydration in solidified systems.

Journal of Hazardous Materials, 2002

The aim of this study is to investigate the effect of four metal nitrate contaminants, namely chr... more The aim of this study is to investigate the effect of four metal nitrate contaminants, namely chromium, manganese, lead and zinc on the mechanical and leaching characteristics of cement-based materials. For this purpose, three different matrices made of: (i) Portland cement, (ii) Portland cement and silica fume, and (iii) Portland cement and natural zeolite were studied. The effects of metals on the stabilised/solidified (S/S) product characteristics were monitored by measuring: (i) setting time, (ii) compressive strength, (iii) acid neutralisation capacity (ANC), and (iv) solubility of the metal contaminants as a function of pH. The results of both mechanical and leaching tests showed the importance of the contaminant/matrix couple considered. Setting time was accelerated in presence of chromium, while in presence of manganese, lead and zinc it was delayed. However, for the last two contaminants, a 10% replacement of cement by silica fume and zeolite, markedly accelerated the setting time compared to the cement-only matrix. Although the early strength development was adversely affected in presence of all four contaminants, the long-term strength was less affected compared to the control materials. Although the ANC of the materials was not markedly affected by the presence of contaminants, the nature of the matrix did modify the ANC behaviour of the solidified materials. The increased strength and reduced ANC observed in the presence of silica fume are both due to pozzolanic reaction. The type of matrix used for solidification did not affect the solubility of the four metal contaminants. Overall, the results showed that the use of blended cements must be carried out with care and the performance assessment of waste-containing cement-based materials must take into consideration both the mechanical and leaching characteristics of the systems.

Chemical Engineering Journal, 2016

Journal of Chemical Technology & Biotechnology

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