Graphene Oxide for Removal of Strontium and Lithium from Aqueous Solutions

Abstract

One of Qatar’s grand challenges is water security, the re-use of water and the introduction of new water resources is an ongoing program of research. Advanced treatment innovations are needed for the treatment of process/produced water. As a major benefit, treated produced water could be used for landscaping, which will decrease the consumption of expensive desalinated water widely used for this purpose. Moreover, there is also a possibility to recover valuable minerals and metals from produced water effluents, considering the large volumes of produced water available. In this project, graphene oxide GO was synthesized for water treatment applications, namely for strontium and lithium removal. These pollutants are found in produced water streams with considerable concentrations. Graphene-based adsorbents are specially chosen to propose a more sustainable adsorbent, ultimately used in a wastewater treatment facility as an alternative or supportive polishing process unit. A review has been undertaken to assess the research to date relating to the ability of GO and its derivatives to adsorb heavy metal ions; the adsorption capacities are reported together with the best-fit isotherm model and the best fit kinetic model. The metals adsorption systems reviewed in detail were arsenic, lead, cadmium, nickel, mercury, chromium, copper and another ten metals were investigated as a collective item. For each heavy metal-GO treatment system, the capacities were compared with several more conventional adsorbents. In this study, GO was characterized and tested to find the maximum capacity, best-fit kinetic model, best-fit isotherm model, and the regenerative ability for the targeted pollutants in simulated produced water and real produced water. The results were then analyzed and compared to other adsorbents to evaluate GO performance. GO has an abundance of oxygen functional groups on its surface. It has a relatively large specific surface area of 232 m2/g and pore volume of 0.4 cm3/g. The GO adsorbents maximum capacities towards strontium and lithium were 131 mg/g and 128 mg/g, respectively. The best-fitting isotherms were the Langmuir and Redlich-Peterson models for strontium and lithium, respectively. The kinetic model best describing the adsorption reactions was the pseudo-second order model for both metal ions. The adsorbent was then regenerated using an eluent (HNO3) to promote desorption of the metals for a potential recovery, with a desorption rate of 96% on the first cycle and retaining an adsorption capacity of well over 80% after three cycles. The adsorbent was then utilized in a binary-component batch experiment involving the two metal ions. The adsorbent capacity decreased for both metals, with the binary system showing a higher adsorbing affinity for strontium. The results showed great promise in the utilization of GO in a multi-stage treatment setup. The project is inspired by the Qatar National Vision 2030, which aims to preserve and protect the environment and one of Qatar’s grand challenges: water security.

Date of Award	2021
Original language	American English
Awarding Institution	HBKU College of Science and Engineering