Single, simultaneous and consecutive biosorption of Cr(VI) and Orange II onto chemically modified masau stones

Abstract

Novel and low cost chemically modified masau stone (CMMS) was investigated for its biosorption of an anionic azo dye, Orange II (OII), and toxic hexavalent chromium (Cr(VI)) from aqueous systems: individually, simultaneously and consecutively. XPS and FTIR analyses indicated the introduction of quaternary-Nitrogen to the CMMS surface after activation with epichlorohydrin (etherifying agent) and diethylenetriamine (crosslinking agent). The effects of pH, contact time and initial concentration (C), and loading order on mechanisms of biosorption/reduction of OII and Cr(VI) onto CMMS were examined in detail. Several analytical techniques were employed to characterise the physio-chemical properties of the CMMS and determine the biosorption mechanisms. The pseudo second order and redox models were able to adequately predict the kinetics of biosorption. The Langmuir maximum OII biosorption capacity (q) was calculated as 136.8 mg/g for the dye onto the Cr(VI)-loaded CMMS consecutive system at C = 100 mg/dm. The q for the Cr(VI) system was found to be 87.32 mg/g at the same C max. This reveals that the biosorption of OII and Cr(VI) mainly takes place via two different mechanisms i.e. hydrogen bonding and electrostatic attraction for the dye, and biosorption-coupled reduction for Cr(VI).

Enhanced removal of acetaminophen from synthetic wastewater using multi-walled carbon nanotubes (MWCNTs) chemically modified with NaOH, HNO3/H2SO4, ozone, and/or chitosan

“…5). This stems from the fact that the higher the dose of the adsorbent, the greater the availability of exchangeable sites for Ace molecules [31].…”

Adsorptive Removal of Hexavalent Chromium by Diphenylcarbazide-GraftedMacadamiaNutshell Powder

“…In a recent study [ 18 ], it was shown that modification of natural Populus tremula fibers with amino ligands led to increased adsorption capacity of acid blue 25 from 22.33 mg/g for unmodified to 48 mg/g for hydrazine fiber and 67 mg/g for ethylenediamine fiber. Masau stones were chemically modified with diethylenetriamine through a cross-linking protocol, and 87.32 mg/g adsorption capacity was reported [ 19 ]. The presence of protonated amino groups at acidic conditions was credited to the biosorption-coupled reduction removal mechanism of Cr(VI).…”

Recent advances in hexavalent chromium removal from aqueous solutions by adsorptive methods

“…Besides the dominant adsorption-reduction mechanism, recent studies have reported three mechanisms all taking place simultaneously, ion-exchange, electrostatic attraction, and reduction. 34,36 The ion exchange mechanism was explained on the basis of the presence of CO 3 2À in the interlayer structures of magnetic particles imprinted cellulose-based biocomposites made from hydrotalcite (HT) and hydroxyapatite (Hap). 36 The electrostatic attraction of chromate anions to the adsorbent's surface could be the result of the presence of higher valence cations like Ca 2+ , Mg 2+ and Fe 3+ in the adsorbent 36 as indicated in Fig.…”

“…The typical study, Masau stones cross-linked with epichlorohydrin (ECH) and graed with diethylenetriamine (DETA) were experimented for the removal of Cr(VI) from aqueous solutions. 34 The adsorption capacity of 87.33 mg g À1 was achieved within 250 min. A complex mechanism of removal involving adsorption of Cr(VI) through electrostatic attraction, hydrogen bonding, and p-p interactions was reported.…”

“…A complex mechanism of removal involving adsorption of Cr(VI) through electrostatic attraction, hydrogen bonding, and p-p interactions was reported. 34 Application of lignocellulose-based materials in metal ion conscation has been covered in several recent reviews. 1,2,114,115,117 Hence, the current review will not attempt to repeat those reviews but will instead focus on the overall trend in adsorbent synthesis and application.…”