Cyclodextrin-Assisted Synthesis of Pd/Co/C Nanopolyhedra by ZIF-67 as a Highly Acid Tolerant Catalyst for Hexavalent Chromium Reduction

Abstract

The palladium/cobalt/carbon (Pd/Co/C) nanopolyhedra were synthesized by calcinating the precursor prepared by a cyclodextrin (CD) modified palladium acetylacetonate loaded on ZIF-67, hydroxypropyl-β-cyclodextrin (HP-β-CD)–[Pd­(acac)2]/ZIF-67. On one hand, the HP-β-CD was used to increase the solubility of Pd­(acac)2 by supramolecular interactions, and on the other hand, ZIF-67 was employed to provide the Co/C as the magnetic support. The Pd/Co/C nanopolyhedra obtained with the assistance of HP-β-CD have high activity and reusability for the reduction of the dichromate ion in the presence of formic acid without using any buffer solution, and no significant leaching of metallic Co of the catalyst was observed. This could be ascribed to the fact that the presence of HP-β-CD could lead to a more homogeneous distribution of metallic Pd in the Pd/Co/C nanopolyhedra, which could prevent the dissolution of metallic Co by formic acid.

Heterogeneous ZnS–zinc carbonate hydroxide micro-belts for Cr(vi) reduction under simulated sunlight

“…[1][2][3] Thus, different strategies have been developed for Cr(VI) removal, such as adsorption, biological and chemical reduction as well as photocatalysis. [4][5][6][7] Among the above methods, the photocatalytic reduction of Cr(VI) to Cr(III) that could further be precipitated by inorganic bases is considered as one of the promising methods because of its eco-friendly nature and high efficiency with solar light in the presence of photocatalysts such as cadmium sulfide (CdS) based composites, CoFe 2 O 4 /BiOBr/graphene composites, CeO 2 /Mg-Al-layered double oxide nanosheets and CuS/ BiVO 4 . [8][9][10][11] In particular, CdS with a narrowband as one of the most promising photocatalysts, has been widely developed due to its efficient visible light responsive ability and good carrier transportation capability.…”

Photocatalytic Reduction and Recognition of Cr(VI): New Zn(II)-Based Metal–Organic Framework as Catalytic Surface

“…As per the recommendation of the World Health Organization (WHO), Cr­(VI) content more than 0.05 mg L –1 in drinking water can be fatal to human health and aquatic organisms . Therefore, continual detection and monitoring of Cr­(VI) concentration is a dire necessity. ,, In 2013, for the very first time, Li et al. reported a cationic luminescent MOF that could selectively detect and capture Cr 2 O 7 2– through fluorescence quenching .…”

“…However, dealing with Cr­(VI) toxicity is challenging, and methods such as ion exchange, adsorption, electrochemical reduction, microbial reduction, photocatalytic reductions, etc. are often employed to remove Cr­(VI) from wastewater. ,,,− Among these, photocatalytic reduction of Cr­(VI) to its nontoxic or comparatively less toxic version, i.e. Cr­(III), has been found to be the frequently used remedy due to its cost effectiveness, less complicated and environmental-friendly protocols with high efficiency, and recycling benefits. − Although most of the photocatalytic reductions have been performed under the influence of UV–vis light, natural sunlight driven catalytic reduction is even most cost-effective and a sustainable method for the treatment of industry effluent carrying toxic Cr­(VI) ions.…”

“…31 Therefore, continual detection and monitoring of Cr(VI) concentration is a dire necessity. 26,32,33 In 2013, for the very first time, Li et al reported a cationic luminescent MOF that could selectively detect and capture Cr 2 O 7 2− through fluorescence quenching. 34 Afterward, many efforts have been devoted to developing new MOF-based fluorescent materials for the detection of dichromate along with other oxoanions.…”

Efficient Photoreduction of Hexavalent Chromium Using the Reduced Graphene Oxide–Sm2MoO6–TiO2 Catalyst under Visible Light Illumination

“…Chromium has two general oxidation levels under relevant natural conditions: Cr­(III) and Cr­(VI). Chromium­(III) is less mobile, less toxic, and easily precipitated as hydroxides, and Cr­(III) is found in many vegetables, fruits, meats, grains, and yeast. − Cr­(VI) is highly active, dangerous, and toxic and present in the wastewater of chrome plating, electroplating, timber treatment, chilling plants, steel and alloy industries, leather tanning, automobiles, and mining industries. The release of Cr­(VI) into the water sources can induce cancer, dermatitis, chronic ulcer, gastrointestinal tract damage, and kidney and lung damage. − As a toxic environmental pollutant that induces harmful effects on human beings, the International Agency for Research on Cancer (IARC) has identified Cr­(VI) as a type I carcinogen.…”