Chromium removal from flocculation effluent of liquid-phase oil-based drill-cuttings using powdered activated carbon

M.J. Ayotamuno, R.N. Okparanma, S.O.T. Ogaji and S.D. Probert

Applied Energy, 2007, vol. 84, issue 10, 1002-1011

Abstract: The practice of injecting the flocculation effluent of liquid-phase oil-based drill-cuttings (LP-OBDCs) into the ground is a popular current disposal-option for this type of drilling waste in Nigeria. Unfortunately, this practice leads to environmental degradation because this flocculation effluent contains high concentrations of chromium (Cr6+), which is a heavy-metal pollutant. Consequently, it is recommended that the flocculation effluent be treated in a batch adsorption process, using powdered activated-carbon (PAC) in order to improve the quality of the flocculation effluent before its sub-surface injection. A representative sample of the untreated LP-OBDC was collected from a mud pit close to an oil-well in the Niger Delta region of Nigeria. Initial characterization of the untreated LP-OBDC showed that the concentration of Cr6+ was 5.26Â g/m3. Flocculation of the LP-OBDCs was carried out using aluminum sulphate and sodium chloride as coagulant and flocculant, respectively. After flocculation, the Cr6+ was reduced to 5.01Â g/m3 (i.e. a 4.75% reduction). The flocculation effluent was then subjected to an activated-carbon batch-adsorption process. At the end of the process, the Cr6+ content was further reduced to 2.77Â g/m3 (i.e. a 44.7% reduction), which shows a significant improvement on the quality of the flocculation effluent. The adsorption mechanism of Cr6+ onto the PAC fitted the second-order kinetic model (with R2Â =Â 1.00 approximately) with equilibrium being attained within 60Â minutes of contact time. Performance characteristics of the PAC show that the maximum adsorption capacity of the adsorbent at equilibrium is 1.60Â mg/g (i.e. a 64.0% adsorption) at the initial chromium-concentration, C0, of 2.50Â g/m3. Also, adsorption-capacity data, obtained using the regressed Freudlich's isotherm (, were quite close to the pertinent experimental data (with R2Â =Â 0.981). The adsorption intensity, n, is 1.32, indicating a strongly favourable adsorption, which shows that a large amount of chromium is adsorbed at low concentrations of adsorbate in the flocculation effluent.

Keywords: Heavy-metal; removal; Oil-based; drill-cuttings; Activated-carbon; adsorption (search for similar items in EconPapers)
Date: 2007
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

Downloads: (external link)
http://www.sciencedirect.com/science/article/pii/S0306-2619(07)00047-5
Full text for ScienceDirect subscribers only

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:eee:appene:v:84:y:2007:i:10:p:1002-1011

Ordering information: This journal article can be ordered from
http://www.elsevier.com/wps/find/journaldescription.cws_home/405891/bibliographic
http://www.elsevier. ... 405891/bibliographic

Access Statistics for this article

Applied Energy is currently edited by J. Yan

More articles in Applied Energy from Elsevier
Bibliographic data for series maintained by Catherine Liu ().