Removal of microcystin-LR and microcystin-RR by graphene oxide: Adsorption and kinetic experiments

• Use of graphene oxide (GO) for removal of microcystin-LR and microcystin-RR is demonstrated.
• High adsorption capacity with 1699.7 μg/g for MC-LR and 1877.8 μg/g for MC-RR was observed.
• The influence of other environmental pollutants on removal of microcystins was examined.
• The performance to GO is superior to that of commercially available activated carbon.
• After adsorption, GO can be regenerated and reused up to 10 times.

Graphene oxide (GO) was employed in the present study for removal of two commonly occurring algal toxins, microcystin-LR (MC-LR) and microcystin-RR (MC-RR), from water. The adsorption performance of GO was compared to that of commercially available activated carbon. Further, adsorption experiments were conducted in the presence of other environmental pollutants to understand the matrix effects of contaminated water on the selective adsorption of MC-LR and MC-RR onto GO. The environmental pollutants addressed in this study included different anions (nitrate (NO3−)(NO3−), nitrite (NO2−)(NO2−), sulphate (SO42−)(SO42−), chloride (Cl−), phosphate (PO43−)(PO43−) and fluoride (F−)) and cations (sodium (Na+), potassium (K+), magnesium (Mg2+) and calcium (Ca2+)). GO showed very a high adsorption capacity of 1700 μg/g for removal of MC-LR and 1878 μg/g for MC-RR while the maximum adsorption capacity obtained with the commercial activated carbon was 1481.7 μg/g and 1034.1 μg/g for MC-LR and MC-RR, respectively. The sorption kinetic experiments revealed that more than 90% removal of both MC-LR/RR was achieved within 5 min for all the doses studied (500, 700 and 900 μg/L). GO could be reused as an adsorbent following ten cycles of adsorption/desorption with no significant loss in its adsorption capacity.

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