Production potentials of massive offshore oil and gas reserves represent a promising source of energy security for the world. However, recent developments in environmental pollution control are drawing attention to the problem of persistent hazardous metal content of produced (formation and injected) water from oil and gas reservoir that are discharged everyday from offshore facilities. The removal of heavy metal has become a very important industrial problem. Present methods for metal recovery from produced water are becoming increasingly undesirable for a number of reasons. The continued success of metal recovery from produced water hinges on the development of new technology.

In this study, a pilot-scale packed-bed reactor has been developed in order to investigate influences of process parameters and their interactions on the recovery of metals from produced water using diatomaceous material. The material was formed into a packed configuration to provide a high adsorbent area-to-aqueous solution volume ratio. Activated carbon and ion-exchange resin were tested for comparison. The results obtained show that flow-rate, residence time, metal concentration loading and packed-bed geometry significantly influenced the efficiency of the reactor system metal recovery and have to be considered in the design of large-scale system. An optimum residence time of 2 hours has been found to give the metal recovery capacities of 60%, 76% and 80% for the ion-exchange resin, diatomaceous material and activated carbon respectively. The sequestered metals were efficiently eluted from the diatomaceous material using different elution solutions for different metals. Selectivity of adsorbent for specific metals can be manipulated on the uptake and elution sides of the process. Present study also revealed that diatomaceous material can be regenerated and used many times over just as conventional adsorbents or ion-exchange resins in process wastewater purification as well as metal recovery processes.

The application of the packed-bed reactor using the readily available diatomaceous material is therefore recommended for economical and cost effective large-scale purification and recovery of metals from oil and gas produced water loaded with metals.

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