Effect of co-presence of NSAIDs with cadmium: i) evaluation of NSAID-bearing water for washing Cd from soil, ii) Cd removal from NSAID-bearing water using magnetic graphene oxide

Cadmium “Cd” is a toxic pollutant that may present in soil and water. This work evaluates: i) the use of non-steroidal anti-inflammatory drugs “NSAIDs”-bearing water for washing soil containing Cd(II), ii) removal of Cd(II) from NSAID-bearing water by adsorption onto magnetic graphene oxide which can be easily separated by strong magnet. The studied NSAIDs are aspirin, ketoprofen, ibuprofern and diclofenac. The Cd(II)-NSAIDs complexes were synthesized and characterized by FT-IR. Graphene was initially oxidized by either nitric acid, or ammonium persulphate method, or Hummer's method. Magnetite was then deposited on graphene oxide to give the corresponding magnetic graphene oxides (NA-MGO, APS-MGO and Hum-MGO, respectively). The effect of the following factors on Cd(II) uptake was investigated: NSAIDs type, pH, graphene oxidation method, magnetite:graphene oxide mass ratio in the adsorbent, (Cd(II):NSAID) molar ratio. Maximum Cd(II) uptake was achieved using “magnetic graphene oxidized with ammonium persulphate where the mass ratio of magnetite to graphene oxide was 2:1” in the presence of diclofenac at pH6. The best Cd(II):diclofenac molar ratio was 1:3. The maximum adsorption capacity of Cd(II) was found to be 83 mg L−1. The regeneration of the adsorbent was possible by 0.3 M HNO3 solution and 80% of adsorption efficiency was maintained after five cycles. Upon presence of co-existing ions, 80% of the adsorption efficiency was maintained. Various NSAIDs-containing waters were used for washing Cd-containing soil; the maximum removal efficiencies of Cd were 18% and 16% using 5 mM diclofenac or 10 mM aspirin, respectively. Using diclofenac or aspirin-spiked real pharmaceutical wastewater gave 28% removal of Cd. The optimum adsorption method was used for removal of Cd(II) from diclofenac-containing soil-washing water, where two successive adsorptions were needed for complete Cd uptake.