Removal of Cr(VI) from aqueous solution using amino‐modified Fe₃O₄–SiO₂–chitosan magnetic microspheres with high acid resistance and adsorption capacity

Abstract

A novel, bioadsorbent material of polyethylenimine-modified magnetic chitosan microspheres enwrapping magnetic silica nanoparticles (Fe 3 O 4 -SiO 2 -CTS-PEI) was prepared under relatively mild conditions. The characterization results indicated that the adsorbent exhibited high acid resistance and magnetic responsiveness. The Fe 3 O 4 loss of the adsorbent was measured as 0.09% after immersion in pH 2.0 water for 24 h, and the saturated magnetization was 11.7 emu/g. The introduction of PEI obviously improved the adsorption capacity of Cr(VI) onto the adsorbent by approximately 2.5 times. The adsorption isotherms and kinetics preferably fit the Langmuir model and the pseudo-second-order model. The maximum adsorption capacity was determined as 236.4 mg/g at 258C, which was much improved compared to other magnetic chitosan materials, and the equilibrium was reached within 60 to 120 min. The obtained thermodynamic parameters revealed the spontaneous and endothermic nature of the adsorption process. Furthermore, the Cr(VI)-adsorbed adsorbent could be effectively regenerated using a 0.1 mol/L NaOH solution, and the adsorbent showed a good reusability. Due to the properties of good acid resistance, strong magnetic responsiveness, high adsorption capacity, and relatively rapid adsorption rate, the Fe 3 O 4 -SiO 2 -CTS-PEI microspheres have a potential use in Cr(VI) removal from acidic wastewater.

One-step synthesis of 1,6-hexanediamine modified magnetic chitosan microspheres for fast and efficient removal of toxic hexavalent chromium

“…For a pH above 6.0, CrO 4 2− is a main form of hexavalent chromium, whereas HCrO 4 − and CrO 4 2− are main forms of hexavalent chromium at pH from 2.0 to 6.0. Whereas H 2 CrO 4 is a major form of hexavalent chromium at pH below 1.0 27 . Therefore, amino groups in both CTS and 1,6-hexanediamine could be protonated to acquire -NH 3 + in acidic medium.…”

“…A simple method to synthesize magnetic CTS NPs by co-precipitation through epichlorohydrin cross-linking process was proposed, and the resultant magnetic CTS showed a 69.4 and 55.80 mg/g of the maximum adsorption capacity for hexavalent chromium 25 , 26 . In a recent work, Liu’s group used the emulsion crosslinking technique to prepare the polyethylenimine modified magnetic SiO 2 –CTS microspheres through four-step procedure, showing enhanced Cr(VI) uptake amount of 236.4 mg/g 27 . Unfortunately, the adsorption process was relatively slow (60–360 min) 24 , 26 , 27 .…”

“…In a recent work, Liu’s group used the emulsion crosslinking technique to prepare the polyethylenimine modified magnetic SiO 2 –CTS microspheres through four-step procedure, showing enhanced Cr(VI) uptake amount of 236.4 mg/g 27 . Unfortunately, the adsorption process was relatively slow (60–360 min) 24 , 26 , 27 . In order to improve the adsorption rate, Hu et al .…”

Magnetically Recyclable Wool Keratin Modified Magnetite Powders for Efficient Removal of Cu2+ Ions from Aqueous Solutions

“…The typical nanomaterial sorbents with magnetic features have been widely studied for the removal of heavy metal species because they have high surface area and are easy to separate from aqueous solutions by applying external magnetic fields [18]. Recently, many magnetite (Fe 3 O 4 ) based adsorbents have been developed by incorporation of chitosan [19], chitosan and calcium alginate [20], chitosan and polyether sulfone [21], polyacrylamidoxime [22], asparagine [23], polyethylenimine [24], ethylenediamine coupled with graphene oxide and chitosan-g-poly(acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid) copolymer [25], TiO 2 and graphene [26], graphene oxide [27], amino acid and graphene oxide [28], carbon [29], polydopamine or polyamidoamine [30], NH 2 -MIL-125 (Ti) [31], organodisulfide [32], curcumin [33], alginate [34], zeolite and cellulose nanofibers [35], and selective adsorbents ethylene diamine tetraacetic acid [36] and N-(trimethoxysilylpropyl) ethylenediamine triacetic acid [37]. For example, the catechol groups of dopamine can integrate with metal ions and increase the hydrophilic ability of asprepared adsorbents [38].…”

Preparation of PEI/CS aerogel beads with a high density of reactive sites for efficient Cr(vi) sorption: batch and column studies

“…27 In addition, when compared to other CS-based membrane or bead-like adsorptive materials, 28,29 magnetic powdery materials have had to be separated from solutions using an extra strong magnet, which would unavoidably result in secondary pollution derived from non-magnetic components. More signicantly, from a practical point of view, there are problems of preparative cost and small particles which might cause bottlenecks for this type of adsorptive material.…”