Removal of barium, cobalt, strontium and zinc from solution by natural and synthetic allophane adsorbents

Abstract

Abstract:The capacity and the mechanism of the adsorption of aqueous barium (Ba), cobalt (Co), strontium (Sr) and zinc (Zn) by Ecuadorian (NatAllo) and synthetic (SynAllo-1 and SynAllo-2) allophanes were studied as a function of contact time, pH and metal ion concentration using kinetic and equilibrium experiments. The mineralogy, nano-structure and chemical composition of the allophanes were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and specific surface area analyses. The evolution of adsorption fitted to a pseudo-first-order reaction kinetics, where equilibrium between aqueous metal ions and allophane was reached within < 10 min. The metal ion removal efficiencies varied from 0.7 to 99.7 % at pH 4.0 to 8.5. At equilibrium, the adsorption behavior is better described by the Langmuir model than by the Dubinin-Radushkevich model, yielding sorption capacities of 10.6, 17.2 and 38.6 mg/g for Ba , 12.4, 19.3 and 29.0 mg/g for HCoO , 7.2, 15.9 and 34.4 mg/g for Sr and 20.9, 26.9 and 36.9 mg/g for Zn , respectively, by NatAllo, SynAllo-2 and SynAllo-1. The uptake mechanism is based on a physical adsorption process. Allophane holds great potential to remove aqueous metal ions and could be used instead of zeolites, montmorillonite, carbonates and phosphates for wastewater treatment.

Magnesium isotope fractionation during hydrothermal seawater-basalt interaction

“…This suggests that the metal ion (Mg) uptake by secondary clay minerals and the related isotope fractionation mechanism are highly dependent on the starting fluid composition (including the pH, concentration of elements required for mineral formation, and the presence or absence of seed crystals and precipitation inhibitors). Furthermore, fractionation also depends on the physicochemical and surface characteristics of the alteration mineral (such as crystal structure and bond lengths, specific surface area, surface charge, etc., Li et al, 2014;Baldermann et al, 2018). Such factors can be further complicated by aqueous solution speciation, as Mg isotope fractionation can occur between individual species (e.g., Schott et al, 2016).…”

Zinc-Containing Effluent Treatment Using Shewanella xiamenensis Biofilm Formed on Zeolite

“…It can be inferred from Figure 5 that the sorption capacity of the mineral-organic sorbent sharply increased with the increase of Zn(II) concentration in solution ( Figure 5 ), from 1.2 to 4.4 mg/L in the Zn-system, from 1.2 to 2.9 in the Zn/Cu/Sr system, from 0.9 to 2.9 in the Zn/Ni/Cu system, and from 0.8 to 2.6 mg/g in the Zn/Cu/Sr/Ba system. At low metal ion concentrations, a large number of available binding sites facilitate metal ion sorption, while at high metal concentrations, the number of binding sites on sorbent surfaces is limited and a sorption maximum has been attained [ 24 ].…”

Removal of heavy metals (Co, Cr, and Zn) during calcium–aluminium–silicate–hydrate and trioctahedral smectite formation

“…The total concentrations of aqueous Na, Al, Ca, Co, Cr, Si and Zn were analysed in acidified aliquots (2% HNO 3 ) by inductively coupled plasma optical emission spectroscopy (ICP-OES) using a PerkinElmer Optima 8300 DV. The analytical precision (2r, 3 replicates) is better than ± 2% for Co and Si analyses and ± 4% for Al, Ca, Cr and Zn analyses, respectively, relative to replicate measurements of NIST 1640a, in-house and SPS-SW2 Batch 130 standards [31].…”

“…C-A-S-H phases share many structural similarities with phyllosilicates. Smectite group minerals, for instance, have a 2:1 layer structure comprising negatively charged octahedral and tetrahedral sheets that are connected to an interlayer site, where hydrated and partly exchangeable cations are intercalated [30][31][32]. The unique structure, besides a small particle size (\ 100 nm), a large specific surface area ([ 10 m 2 /g), and presence of surface functional groups (i.e.…”