Cost-Effective Preparation of Gold Tailing-Based Aerogels for Efficient Adsorption of Copper Ions from Wastewater

Abstract

Water pollution caused by heavy metal ions has attracted worldwide attention. In this work, gold tailings were used as raw materials and the sol–gel method combined with the atmospheric pressure drying method were used to achieve the low-cost preparation of a silica aerogel. (3-Aminopropyl) triethoxysilane (APTES), ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), and chitosan were used to modify the silica aerogel, which was then used as an adsorbent for the adsorption of copper ions in wastewater. The adsorbent type, adsorption time, copper ion concentration, and pH value were investigated as variables to explore the best adsorption conditions. The adsorption mechanism was also elaborated on. The crystal structure, surface morphology, surface functional groups, chemical composition, and specific surface area of the aerogels and the modified aerogels were characterized by various physiochemical characterizations such as XRD, SEM, FT-IR, XRF, and BET. The results showed that the prepared silica aerogel contained 91.1% SiO2, mainly amorphous SiO2, and amino and carboxyl groups. Other functional groups were successfully grafted onto the silica aerogels. The original silica aerogels and modified silica aerogels had a large specific surface area, total pore volume, and pore diameter. When copper ions were adsorbed by the chitosan-modified silica aerogels, the adsorption capacity of the copper ions was the highest (33.51 mg/g) under the conditions of a copper ion concentration of 100 mg/L, a pH value of 7, and an adsorption time of 2 h. The adsorption of Cu2+ was mainly due to the ion exchange and electrostatic gravity.

Silicon–Carbon Dots-Loaded Mesoporous Silica Nanocomposites (mSiO2@SiCDs): An Efficient Dual Inhibitor of Cu2+-Mediated Oxidative Stress and Aβ Aggregation for Alzheimer’s Disease

“…Furthermore, the adsorption kinetics revealed that the adsorption process reached a plateau within 5 min, indicating the quick capture of Cu 2+ by mSiO 2 @SiCDs (Figure 3C), with a faster rate than those of the previously reported APTMSfunctionalized silica 38 and EDTA-2Na-modified silica aerogel. 28 Both pseudo-first-order (correlation coefficient R 2 = 0.9947) and pseudo-second-order (R 2 = 0.9945) adsorption kinetics models fitted well with the adsorption process, indicating that physisorption and chemisorption coexisted. 39,40 In addition, the adsorption isotherm manifested that the equilibrium adsorption amount (Q e ) of mSiO 2 @SiCDs for Cu 2+ gradually increased with the elevated Cu 2+ concentration (0.1−10 mM) (Figure 3D), which might be favorable for mSiO 2 @SiCDs to capture Cu 2+ of high concentration, such as for the excess Cu 2+ associated with AD (∼0.4 mM).…”

“…23 According to the adsorption isotherm fitting results, both the Langmuir model (R 2 = 0.9895) and Freundlich model (R 2 = 0.9870) fitted well with favorable R 2 . The good fitting of the Langmuir model revealed that the theoretical maximum adsorption capacity (Q max ) of mSiO 2 @SiCDs for Cu 2+ could reach 3.02 mmol/g (Figure 3D), which was higher than those of the reported EDTA-2Na-modified silica aerogel (∼0.30 mmol/g), 28 APTMS-functionalized silica (∼0.53 mmol/g), 38 and amine silane-modified mesoporous silica (1.96 mmol/g). 41 These results demonstrate the superior affinity of mSiO 2 @ SiCDs toward Cu 2+ to other comparable materials, e.g.…”

“…In order to improve the feasibility and chelating ability of SiCDs toward Cu 2+ , the biocompatible mSiO 2 nanoparticles with a high surface area and an abundantly porous structure were deliberately adopted to load and gather SiCDs with the interaction between residual silane groups on SiCDs and silanol groups of mSiO 2 . Compared with the tedious functionalization process of EDTA onto silica, , the prepared SiCDs could be easily modified onto mSiO 2 via a one-step reaction; meanwhile, the local enrichment of SiCDs onto mSiO 2 was possibly realized, thus leading to the enhancement of Cu 2+ chelating performance of mSiO 2 @SiCDs. Furthermore, by virtue of the Cu 2+ chelating effect, mSiO 2 @SiCDs could realize the modulation of the enzymic activity of free Cu 2+ and the Aβ 42 –Cu 2+ complex, inhibiting the peroxidase (POD) activity to lower the generation of the hydroxyl radical ( • OH) while reserving the superoxide dismutase (SOD) activity of Cu 2+ to scavenge the superoxide anion (O 2 •– ), further alleviating the cellular oxidative stress induced by the Aβ 42 –Cu 2+ complex.…”

Recent Advances on Porous Siliceous Materials Derived from Waste

“…130 million tons [ 132 ]). The general composition of different mining wastes is reported in Table 3 [ 133 , 134 , 135 , 136 , 137 , 138 ].…”

Chitosan–Silica Composite Aerogel for the Adsorption of Cupric Ions

“…The strategy developed in this work is a synthetic opportunity, because although a plethora of materials have already been reported for the removal of Cu(II) [ 18 ], research into aerogels, as gels whose liquid part is replaced by a gas, and specifically into aerogels based on both chitosan and silica, is still very limited for this application field [ 19 , 20 ]. Furthermore, we describe a simpler aerogel synthesis procedure in a one-pot fashion that requires no additional stages likes silylation, and the chitosan and silica phases are covalently bonded using silica as the crosslinker, unlike other hybrids in the literature [ 21 , 22 , 23 , 24 , 25 , 26 ].…”