Efficient Removal of Heavy Metals from Polluted Water with High Selectivity for Mercury(II) by 2-Imino-4-thiobiuret–Partially Reduced Graphene Oxide (IT-PRGO)

Abstract

A novel chelating adsorbent, based on the chemical modification of graphene oxide by functionalization amidinothiourea to form 2-imino-4-thiobiuret-partially reduced graphene oxide (IT-PRGO), is used for the effective extraction of the toxic metal ions Hg(II), Cu(II), Pb(II), Cr(VI), and As(V) from wastewater. FTIR and Raman spectroscopy, XRD, and XPS confirm the successful incorporation of the amidinothiourea groups within the partially reduced GO nanosheets through nucleophilic substitution reactions with the acyl chloride groups in the chemically modified GO. The IT-PRGO adsorbent shows exceptional selectivity for the extraction of Hg(II) with a capacity of 624 mg/g, placing it among the top of carbon-based materials known for the high capacity of Hg(II) removal from aqueous solutions. The maximum sorption capacities for As(V), Cu(II), Cr(VI), and Pb(II) are 19.0, 37.0, 63.0, and 101.5 mg/g, respectively. The IT-PRGO displays a 100% removal of Hg(II) at concentrations up to 100 ppm with 90%, 95%, and 100% removal within 15, 30, and 90 min, respectively, at 50 ppm concentration. In a mixture of six heavy metal ions containing 10 ppm of each ion, the IT-PRGO shows a removal of 3% Zn(II), 4% Ni(II), 9% Cd(II), 21% Cu(II), 63% Pb(II), and 100% Hg(II). A monolayer adsorption behavior is suggested based on the excellent agreement of the experimental sorption isotherms with the Langmuir model. The sorption kinetics can be fitted well to a pseudo-second-order kinetic model which suggests a chemisorption mechanism via the amidinothiourea groups grafted on the reduced graphene oxide nanosheets. Desorption studies demonstrate that the IT-PRGO is easily regenerated with the desorption of the metal ions Hg(II), Cu(II), Pb(II), Cr(VI), and As(V) reaching 96%, 100%, 100%, 96%, and 100%, respectively, from their maximum sorption capacities using different eluents. The IT-PRGO is proposed as a top performing remediation adsorbent for the extraction of heavy metals from waste and polluted water.

Recent Advances in Applications of Hybrid Graphene Materials for Metals Removal from Wastewater

“…Similarly, GOMCS-IL suffered a slight loss in adsorption capacity after 4 cycles of adsorption-desorption, indicating good recyclability of GOMCS-IL [33]. IT-PRGO was also reusable and very efficient in adsorbing Pb (II) [47]. Mg−Al LDH/ pRGO was effectively regenerated using HCl as an eluting agent and was reusable without loss in removal efficiency [26].…”

“…The best performing graphene composites for mercury removal were modified with organic compounds. The five highest capacities reported all utilizes organic compounds in preparation of the adsorbents [36,44,47,76,129,130].…”

“…High adsorption capacities of mercury in the range of 168-700 mg/g have been obtained with different graphene composites [36,47,[129][130][131][132][133][134][135]. The synthesis process of 2, 20-dipyridylamine (DPA) was a simple precipitation in the presence of nitrogen gas.…”

A Polymerization‐Cutting Strategy: Self‐Protection Synthesis of Thiol‐Based Nanoporous Adsorbents for Efficient Mercury Removal

“…Water is a vitally important resource for human life. However, with the rapid generation of an enormous amount of detrimental chemical waste from various industries, water pollution has been a serious worldwide problem for several decades . As one of the hazardous metal ions, mercury has drawn increasing attention due to its poisonous and harmful effects on human health.…”

“…However, with the rapid generation of an enormous amount of detrimental chemical waste from variousi ndustries, water pollution has been as erious worldwide problem for severald ecades. [1][2][3][4] As one of the hazardousm etal ions, mercury has drawn increasinga ttentiond ue to its poisonous and harmful effects on human health. Notably,t he soluble divalent mercury ions (Hg 2 + )c an be easily transferred into highert oxic organometallic forms via biological methylation.…”