A viable and cost-effective technology was explored in this present task for removal of heavy metal ions such as Cu 2+ , Ni 2+ , Zn 2+ , Cd 2+ , and Pb 2+ from aqueous solution using three fruit peels such as orange peel (OP), lemon peel (LP), and banana peel (BP). The surface of the LP and lemon peel cellulose (LPC) was chemically modified. All these adsorbents were characterized by FT-IR, BET, and SEM. The widely used Langmuir adsorption isotherms were used to describe the adsorption equilibrium process. The adsorption capacity of metal ions such as Cu 2+ and Ni 2+ was found to be more than that of other metal ions. Upon comparison of the adsorbents, surface modified LPC (LPCACS) was found to show enhanced adsorption activity. A comparative study of adsorption was carried out with activated carbon (AC) also from which it was inferred that the order of the adsorption capacity is as follows: LPCACS > LPC > AC > LP.
This paper describes the simple hydrothermal preparation of self-adsorbing mesoporous materials using hexadecyltrimethyl ammoniumbromide (HDTMAB) as the template without any functionalization. The template was readily removed upon calcination, as confirmed through Fourier transform infrared spectroscopic analysis. The effects of preparation methods were explored under various experimental conditions. We found that the temperature, time, calcination conditions, and pH all affected the distribution of pore sizes and the surface area, whereas higher pH (strong base) did not favor the preparation of a porous medium because of OH inhibition. We obtained a relatively high surface area (1568.72 m 2 • g -1 ) and large pore size (3.07 nm) under the optimal reaction conditions. A study of the Langmuir adsorption of metal ions (e.g., Pb 2+ , Cu 2+ , Ni 2+ ) revealed that it was a physical phenomenon with the maximum adsorption occurring for the sample prepared under the optimized experimental conditions, with Pb 2+ (6.61 mg • g -1 ) exhibiting enhanced adsorption relative to Cu 2+ (3.46 mg • g -1 ) and Ni 2+ (2.25 mg • g -1 ) because of its larger ionic radius and higher electronegativity. Thus, such as-synthesized mesoporous materials hold great potential for use in the removal of heavy metal ions from aqueous solutions compared to commercially available powdered activated carbon (PAC).
A simple approach based on the covalent grafting of 3-mercaptopropyltrimethoxysilane groups onto the framework of two types of mesoporous silica C16 (surface area: 1568.72 m 2 /g; pore size: 3.07 nm) using hexadecyltrimethyl ammoniumbromide and C9 (surface area: 779.83 m 2 /g; pore size: 4.51 nm) using nonyltrimethyl ammoniumbromide as templates has been reported. Various techniques were employed to confirm the thiol functionalization. A considerable decline in the surface area, pore volume, and interestingly an enhancement in the pore size were observed for functionalized materials. The functionalized derivatives were able to bind quantitatively several folds Ag þ and Hg 2þ ions compared to that of unmodified mesoporous silica and a comparative study with earlier reports indicated that the mesoporous silica discussed in this present work showed superior adsorption behavior. Mercapto-functionalized mesoporous silica have not only exhibited an enhanced adsorption rate towards Ag þ and Hg 2þ but also demonstrated that the maximum adsorption capacity of Ag þ (C16 ¼ 0.73 mg/g; C16-SAn ¼ 192.31 mg/g; C16-SH ¼ 250.00 mg/g; C9 ¼ 0.66 mg/g; C9-SAn ¼ 181.82; C9-SH ¼ 185.85 mg/g) and Hg 2þ (C16 ¼ 0.40 mg/g; C16-SAn ¼ 114.94 mg/g; C16-SH ¼ 126.58 mg/g; C9 ¼ 0.31 mg/g; C9-SAn ¼ 108.70; C9-SH ¼ 112.36 mg/g) is hundred times higher than that of unmodified mesoporous silica. Thus, it is evident that these thiol-functionalized mesoporous silica can be promising adsorbents for the treatment of Hg 2þ and Ag þ contaminants in aqueous solution.Abbreviations: BET, Brunauer-Emmett-Teller; FT-IR, Fourier transform infrared; HDTMDB, hexadecyltrimethyl ammoniumbromide; MPTMS, 3-mercaptopropyltrimethoxysilane; NTMAB, nonyltrimethyl ammoniumbromide; SEM, scanning electron microscopy 775
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