An Enhanced Reduction–Adsorption Strategy for Cr(VI): Fabrication and Application of L-Cysteine-doped Carbon@Polypyrrole with a Core/Shell Composite Structure

Abstract

Reclamation and recycling of heavy metal ions can offer environmental protection and sustainable development. Here, we report the preparation of L-cysteine (L-cys)-doped glucose carbon sphere (GCS)@polypyrrole (PPy) composites (GCS@PPy/L-cys). The adsorption performance and mechanism of GCS@PPy/L-cys toward Cr­(VI) from water were investigated in detail. The chromate enrichment on GCS@PPy is significantly facilitated by doping with L-cys, which prevents the oxidative collapse of the structure. This approach leads to many reduction–adsorption sites that reduce the highly hazardous Cr­(VI) into less toxic Cr­(III). More significantly, the composite can be reused to fabricate supercapacitors that avoid secondary pollution. This strategy offers high-efficiency treatment and sustainable utilization of hypervalent metals in water.

Polypyrrole-based adsorbents for Cr(VI) ions remediation from aqueous solution: a review

“…It has large specific surface area for adsorption but commercial AC is typically expensive hence cheaper and renewable agricultural raw material have been utilised for the fabrication of AC and biochar. Due to the outstanding adsorption properties (Ghosh et al 2020) they can be used in PPy doping to produce Cr(VI) ions exceptional adsorbents and several studies have been reported to this end (Thamilarasu et al 2012;Wang et al 2013;Omwoyo et al 2015;Chen et al 2020;Li et al 2020;Reis et al 2021). Furthermore, dispersed graphene oxide (GO), is capable of providing highly active PPy-based nanocomposite with remarkable Cr(VI) ions removal efficiency (Setshedi et al 2015).…”

“…Overally, the adsorption mechanisms of PPy-based adsorbents appeared to have taken place by the reduction of Cr(VI) species to Cr(III) species under acidic conditions. In the meantime, the amine group (ÀNHÀ) of PPy is partially oxidised to the positively charged species (-NH•þ) which can attract Cr(VI) ions (Li et al 2020). Thus, the adsorption process was associated with ion exchange, electrostatic attractions, complexation, chelation reactions with protonated sites and reduction (Tran et al 2019;Liu et al 2021;Mdlalose et al 2021).…”

“…Several adsorbents have been documented for Cr(VI) ions removal. However, some challenges have been encountered including, tedious and expensive methods of preparation, generation of additional solid wastes, low adsorption capacities owing to the low specific surface areas and unavailability of active functional groups (Dinker and Kulkarni 2015;Liu et al 2017;Hato et al 2019;Du et al 2020;Li et al 2020). It is worthy reviewing polypyrrole (PPy)-based adsorbents because of their unique and enhanced properties PPy has shown great prospects in adsorption application due to its reputable environmental stability, extraordinary conductance, desirable redox properties and easiness of processing (Das and Prusty 2012;Maity et al 2019).…”

“…Lower pH typically demonstrates an improved adsorption capacity attributable to robust electrostatic attractions between aqueous Cr(VI) ions and protonated amine groups of the PPy moiety. The reduction in adsorption capacity as the original solution pH increases was largely a result of the waning electrostatic interactions between adsorbent and Cr(VI) ions as well as their competitive adsorption of Cr(VI) ions and OH À on PPy-based adsorbents adsorption sites(Amalraj et al 2016a;Li et al 2020;Shao et al 2021). Chemical redox reaction occurrence during the Cr(VI) ions adsorption process is validated by application of the Fourier Transform Infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy, Xray adsorption near edge structure (XANES) analysis techniques for the adsorbent before and after Cr(VI) ions adsorption(Mdlalose et al 2018;Chigondo et al 2019;Tran et al 2019).…”

Novel and Green Fe3O4@Sio2-L-Cys Magnetic Absorbent for Efficient Removal of Pb (II) from Aqueous Solution

“…Meanwhile, cysteine is also known as L-cysteine. Safe and non-toxic can effectively reduce the secondary pollution to the environment during water treatment [19].…”