Photoinduced adsorption of Cr(VI) ions in nano‐zinc oxide and nano‐zinc oxide/polypyrrole composite

Abstract

Zinc oxide-polypyrrole composites (ZnO-PPY) are novel materials that have attracted significant attention in recent years. These materials have the potential to remove hazardous pollutants from water effectively. Here, we explore facile synthesis, characterization, and adsorption capacity of hexavalent chromium anions, by nano-ZnO and nano-ZnO-PPY composite. Cold precipitation of ZnO using sodium dodecyl sulfate as an additive prevents nanoparticle growth, which permits the composite preparation with PPY. The results demonstrated that the ZnO-PPY structure was different than ZnO, more amorphous, less porous, and with a different morphology. New Fourier transform infrared spectroscopy vibrations observed in ZnO-PPY hinted an interaction with ZnO, leading to a more acidic surface. This information could point to the composite formation driven by interactions between oxygen groups and pyrrole nitrogen. Both materials performed better under light, indicating a photoinduced adsorption phenomenon favored by oxygen vacancies. The new composite demonstrated a reduced adsorption capacity compared to ZnO at neutral and slightly acidic pHs due to electrostatic repulsion of the negatively charged surface and Cr(VI) anions. At alkaline pHs, the pyrrolic nitrogen's is able to interact with partially charged Cr-complex and to carry out a ligand interchange even in a not favorable charge environment. The ZnO-PPY composite, outperformed the zinc oxide capacity.adsorption, composites, porous materials, surfaces and interfaces | INTRODUCTIONChromium is a heavy metal commonly produced and employed in industrial processes. The industries with the major Cr-emissions to the atmosphere are: coal combustion, steel, and iron management, cement production, tanning processing, catalysis, Cr-plating, and so forth. 1 Presently, chromium is one of the most hazardous pollutants found in wastewater and water reservoirs. Its ingestion causes several health afflictions at both short and long-term exposures, including acute effects such as gastrointestinal disorders, hemorrhagic diathesis, and convulsions. 2 Furthermore, hexavalent chromium has been classified by the International Agency for Research on Cancer as carcinogenic to humans (Group 1), and the WHO recommends an LD 50 of 20-250 mg/kg of hexavalent chromium. For that reason,

Facilitated Adsorption of Mercury(II) and Chromium(VI) Ions over Functionalized Carbon Nanotubes

“…Several functional materials have been developed to remove heavy metals from water to prevent their consequences and promote water purification [ 14 , 21 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. These materials promoted the removal of heavy metals from water by various techniques like adsorption [ 32 , 33 ], ion exchange [ 34 , 35 ], membrane separation [ 36 ], coagulation [ 37 ], chemical precipitation [ 38 ], extraction [ 39 ], dialysis [ 40 ], electrochemical separation [ 41 ] and more.…”

“…The additional advantage of adsorption is its high selectivity and enrichment factor [ 42 ]. Because of its importance, several adsorbents such as activated carbon [ 1 ], biochar [ 1 ], hydroxyapatite/Fe 3 O 4 /polydopamine [ 2 ], polyacrylonitrile–based porous carbon [ 3 ], vesicular basalt rock [ 6 ], activated carbon [ 7 ], ferrihydrite [ 8 ], exopolysaccharides [ 9 ], chitosan/bentonite composite [ 10 ], amine–incorporated UIO–66–NH 2 [ 20 ], silica nanoparticles [ 24 ], graphene oxide−MnFe 2 O 4 Magnetic Nanohybrids [ 25 ], zinc oxide [ 26 ], ZnS [ 31 ], and carbon nanotubes [ 43 , 44 , 45 ] were developed and verified their efficiency in removal of several heavy metals. Compared to these, carbon nanotubes (CNTs) are fascinating due to their unique physical, chemical, and mechanical properties [ 46 , 47 ].…”