Biosurfactant-facilitated leaching of metals from spent hydrodesulphurization catalyst.

AIMS: To investigate the capabilities of different types of biosurfactants (rhamnolipids, lipopeptides, sophorolipids) to remove metals and carbon from the hazardous spent hydrodesulphurization (HDS) catalyst generated by petroleum refineries. METHODS AND RESULTS: Biosurfactants were prepared and used to treat spent HDS catalyst. Metal and carbon contents were analysed and compared with those from no-biosurfactant control treatments. All biosurfactant treatments increased carbon loss percentage from the spent HDS catalyst. The lipopeptide treatment LI, containing 17·34 mg ml-1 of crude biosurfactants, caused the highest carbon loss percentage (44·5%). Rhamnolipids were, in general, better than sophorolipids and lipopeptides as metal-removing agents. The metal content decreased as the concentration of rhamnolipids decreased. The R5 treatment, which contained 0·4 mg l-1 of crude rhamnolipids, caused the highest reduction in metal content. Molybdenum, nickle and vanadium contents were reduced by 90, 30 and 70% respectively. CONCLUSIONS: Biosurfactants might have potential application for metals and coke removal from spent HDS catalysts. The bioleaching capability depends on the type and concentration of the biosurfactant. SIGNIFICANCE AND IMPACT OF THE STUDY: This study, after further in-depth investigations, might lead to the development of an eco-friendly and economic technology to treat or even regenerate the environmentally hazardous spent HDS catalysts, which are generated in huge amounts by the petroleum refineries.

Options and processes for spent catalyst handling and utilization.

The quantity of spent hydroprocessing catalysts discarded as solid wastes in the petroleum refining industries has increased remarkably in recent years due to a rapid growth in the hydroprocessing capacity to meet the rising demand for low-sulfur fuels. Due to their toxic nature, spent hydroprocessing catalysts have been branded as hazardous wastes, and the refiners are experiencing pressure from environmental authorities to handle them safely. Several alternative methods such as reclamation of metals, rejuvenation and reuse, disposal in landfills and preparation of useful materials using spent catalysts as raw materials are available to deal with the spent catalyst problem. The technical feasibility as well as the environmental and economic aspects of these options are reviewed. In addition, details of two bench-scale processes, one for rejuvenation of spent hydroprocessing catalysts, and the other for producing non-leachable synthetic aggregate materials that were developed in this laboratory, are presented in this paper.

Laser ablation of gall bladder stones.

Study of laser interaction with calculi is presented. A system of Nd-Yag and Ho-Yag pulsed lasers were used to produce fluorescence and plasma signals at the stone surface surrounded by saline and bile fluids. Fourth harmonic from Nd-Yag laser was transmitted to the samples by graded UV optical fibres. Gall bladder stones of various compositions were subjected to the high power Ho-Yag laser. Temporal transients and spectral evolution of plasma and fluorescence signals were monitored by a streak camera. A profile of acoustic pressures generated by shock waves was recorded with sensitive hydrophones placed in the surrounding fluids. Ablation threshold, cavitation process and fluorescence dependence on the laser parameters were studied in detail. Potential of stone identification by fluorescence and possible hydrodynamic model for ablation of biological samples is discussed.

Measurement of fluorescence decay of crude oil: a potential technique to identify oil slicks.

The single photon counting technique has been used to measure the decay time for several Kuwaiti crude and refined oils. Fluorescent characteristics of two different bunker oils from widely separate geographic areas have been studied. Laser induced fluorescent data for the crude oil samples are compared with the decay time results to evaluate the potential of these techniques for the identification of oil sticks in the marine environment. Response of the oil film thickness to various excitation wavelengths from a CW Ar ion laser and a pulsed xenon lamp has been investigated.