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

Abstract

Anthropogenic activities are principally responsible for the manifestation of toxic and carcinogenic hexavalent chromium (Cr(VI)) triggering water pollution that threaten the environment and human health. The World Health Organisation (WHO) restricts Cr(VI) ions concentration to 0.1 and 0.05 mg/L in inland surface water and drinking water, respectively. The available technologies for Cr(VI) ions removal from water were highlighted with emphasis on adsorption technology. Furthermore, the characteristics of several polypyrrole-based adsorbents were scrutinized including amino containing compounds, biosorbents, graphene/graphene oxide, clay materials and many other additives with reported effective Cr(VI) ions uptake. This efficiency in Cr(VI) ions adsorption is attributed to enhanced redox properties, increased number of functional groups and well as synergistic behaviour of the materials making up the composite. The Langmuir isotherm best described the adsorption processes with maximum adsorption capacities ranging from 3.40–961.50 mg/g. The regeneration of Cr(VI) ions laden adsorbents was studied. Ion exchange, electrostatic attractions, complexation, chelation reactions with protonated sites and the reduction were the mechanisms of adsorption. Nevertheless, there are limited details on comprehensive adsorbent regeneration studies to prolong robustness in adsorption-desorption cycles and utilization of the Cr(VI) ions laden adsorbent in other areas of research to limit the threat of secondary pollution.

Advances in Sorptive Removal of Hexavalent Chromium (Cr(VI)) in Aqueous Solutions Using Polymeric Materials

“…Chigondo et al had previously reviewed the removal of Cr(VI) using PPy-based adsorbents [ 7 ]. They summarized the removal efficiencies of varied PPy adsorbents, and the mechanisms of Cr(VI) removal and methods for the regeneration of these PPy-based adsorbents were also reported [ 7 ].…”

“…Chigondo et al had previously reviewed the removal of Cr(VI) using PPy-based adsorbents [ 7 ]. They summarized the removal efficiencies of varied PPy adsorbents, and the mechanisms of Cr(VI) removal and methods for the regeneration of these PPy-based adsorbents were also reported [ 7 ]. Bearing the merits of reputable environmental stability, extraordinary conductance, desirable redox properties, ease of processing, and rich in amine groups, PPy has shown great prospects in sorptive removal of Cr(VI) ( Table 1 ).…”

“…The enhanced reduction of Cr(VI) to Cr(III) and the increased electrostatic attractions between chromium and PPy-based adsorbents jointly contributed to Cr(VI) removal at pH ~ 2.0 [ 35 ]. Except that the maximum adsorption generally occurred in the strong acid medium, the oxidation of these PPy-based adsorbents might result in the rupture of the polymer chain to reduce the adsorption [ 7 ] ( Table 1 ). Therefore, more efforts are necessary to minimize the structural deterioration of PPy-based adsorbents and acid consumption during the removal of Cr(VI).…”

“…Bearing the merits of low-cost, large surface area, high selectivity, and high adsorption capacity, polymeric materials have attracted increasing attention in removing Cr(VI) [ 5 ], which can be reflected by the sharply increasing papers published in this field (more than 300 papers in recent decades). Polypyrrole (PPy), polyaniline (PANI), polysaccharides, chitosan, and cellulose have been applied for removing Cr(VI) in wastewater [ 7 , 8 , 9 , 10 , 11 ] ( Figure 1 ). Mechanisms of ion exchange, electrostatic attraction, ligand exchange, reduction, chelation, and hydrogen bonding were involved in Cr(VI) removal.…”

Bioresourced fillers for rubber composite sustainability: current development and future opportunities

“…As a result, the NFreinforced rubber composites are sensitive to water/moisture. The amount of water absorption has increased with increasing fiber loading in the composites 249 . This characteristic is very often limiting the NF-reinforced composites application in many areas.…”