Abstract
Graphene oxide (GO) has excellent physicochemical properties and is used in multiple areas. However, the potential toxicity and environmental problems associated with GO increase its risk to the ecological system. In this study, cement was employed as a coagulant to eliminate GO from aqueous solutions. The effects of the cement dosage, the contact time, and the concentration and volume of the aqueous GO solution on the GO coagulation capacity were investigated in detail. The results showed that the dosage of cement had a significant effect on the coagulation process, and coagulation equilibrium was achieved in less than 1 h. Compared to coagulants used to remove GO from water in other reports, cement exhibited an ultrahigh coagulation capacity of approximately 5981.2 mg/g with 0.4 mg/mL GO solution. The kinetic analysis showed that the GO removal behavior could be described by a pseudo second-order model. The in-depth mechanism of GO coagulation using cement included Ca2+-induced coagulation of GO and adsorption by the hydrated product of cement paste. The present study revealed that cement could be a very cheap and promising material for the efficient elimination of GO from aqueous solutions.
Highlights
Graphene oxide (GO) is one of the most important graphene derivatives and has many unique features, such as excellent mechanical properties, high surface functionalization, high surface area and good dispersibility in aqueous solutions [1]
The potential toxicity and high mobility of GO can cause serious long-term cumulative toxic effects in living organisms, and it has been demonstrated that GO and its derivatives can accumulate in the lung, liver and spleen for a long time [12,13,14]
Cement was employed to remove GO from an aqueous solution, and the effects of the cement dosage, the GO concentration and volume, and the amount of hydrated cement paste prepared with different contact times, on GO coagulation behavior were investigated in detail
Summary
Graphene oxide (GO) is one of the most important graphene derivatives and has many unique features, such as excellent mechanical properties, high surface functionalization, high surface area and good dispersibility in aqueous solutions [1]. Many technologies have been applied to deal with various pollutants (e.g., organic dyes and heavy metal ions), including ion exchange [17,18], adsorption [19,20], coagulation [21], chemical precipitation [22] and membrane separation [23] In comparison with these technologies, coagulation has been considered a promising potential method for the removal and aggregation of GO or other nanomaterials. A study by Yuan et al found that calcined MgAl-layered double hydroxides (MgAl-LDH) showed moderate removal capacity of 984.2 mg/g towards GO, due to the memory effect of calcined LDH [20] These methods for removing GO are slow and time-consuming because of the dominance of physical absorption or coagulation in most cases. Cement was employed to remove GO from an aqueous solution, and the effects of the cement dosage, the GO concentration and volume, and the amount of hydrated cement paste prepared with different contact times, on GO coagulation behavior were investigated in detail
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