With the rapid development of industry and economies across the world, the problem of environmental pollution in aquatic environments has become one of the key issues facing the World. Consequently, the development of efficient and sensitive analytical techniques to determine the levels of organic pollutants in water environments and cost-effective strategies to remove these pollutants, are now more important than ever before. In this thesis, sensitive and selective electrochemical sensors with very good long-term stability were developed for the detection of 4-chloro-2-methylphenoxyacetic acid (MCPA), p-nitrophenol (p-NP), metronidazole (MTZ), and levofloxacin (LEVO). Two strategies were employed in the development of these sensors. Firstly, glassy carbon electrode (GCE) was activated to generate active sites to enhance the electron-transfer process. Secondly, binder-free nanocomposites were employed to facilitate the detection of MCPA, p-NP, MTZ and LEVO. The nanocomposites included graphene, bismuth and copper nanostructures. These were all formed using electrodeposition, avoiding the need to use binders that are typically employed with drop casting. Using these approaches, impressive limits of detection of 8.0 nM, 0.18 nM, 0.9 nM and 11.86 nM were achieved in the electrochemical detection of (1) MCPA at activated GCE, (2) p-NP with bismuth dendrites deposited onto activated GCE, (3) MTZ with the sequential electrodeposition of graphene nanoplatelets (Gr) and bismuth and (4) LEVO with the sequential electrodeposition of Gr and copper at GCE, respectively. Further, graphene supported magnetic nanocomposites (Gr/Fe) were fabricated and used as adsorbents for the potential removal of MCPA, p-NP, MTZ and LEVO from aquatic environments. Iron nanostructures were employed as the magnetic component. These nanocomposites not only prevent the aggregation of the graphene sheets, but also can endow graphene with magnetic properties. This makes the magnetic graphene adsorbents easy to separate by external magnetic fields, greatly simplifying the recycling process. The adsorption kinetics and adsorption isotherms were studied, and the reproducibility, selectivity and reusability of the magnetic Gr/Fe composites were evaluated.