Strengthening the surface and adsorption properties of diatomite for removal of Cr(VI) and methylene blue dye

Abstract

The main purpose of this work was to boost the surface and adsorption characteristics of diatomite (D) through chemical modifications with chitosan (DC), chitosan/titanium isopropoxide (DCTi), or chitosan/ graphene oxide (DCGr), respectively. Physicochemical characteristics of the prepared samples were investigated using SEM, TEM, XRD, FTIR, TGA, and porosity measurements. The impact of such modifiers into the D surface on the removal efficiency of chromium (VI) ions and methylene blue dye was studied in an equilibrium mode. Langmuir and Freundlich isotherms were used to analyze the adsorption data. Modifiers considerably enhanced the surface and textural properties of D through insertion of the main surface functional groups of chitosan and graphene oxide together compared to chitosan and titanium isopropoxide together or chitosan alone. In addition, the total surface area and total pore volume parameters of the unmodified D sample were improved greatly from 16.5 m2/g, 0.036 cm3/g to 39.8 m2/g and 0.174 cm3/g for DCGr, while they were 17.7 m2/g and 0.132 cm3/g for DC. The best adsorption results were well-defined with the Langmuir isotherm equilibrium model. Accordingly, the DCGr sample exhibited the highest uptake of Cr(VI) (about 167 mg/g) and methylene blue (66.7 mg/g). Hence, the chemical modification strategy of diatomite performed by using chitosan and graphene oxide significantly boosted the surface active sites and porosity properties and thus gave rise to the high adsorption capacity of Cr(VI) and methylene blue dye from wastewater. Hence, these findings affirmed the validity of the current strategy for surface modification of diatomite with chitosan and graphene oxide.

Dyes and Heavy Metals Removal from Aqueous Solutions Using Raw and Modified Diatomite

“…The FTIR spectra for the D1 and D2 samples were recorded and presented in Figure 2. The transmittance at 467-468 cm −1 is associated with the Si-O-H stretching vibration, and the strong peak at 1092-1094 cm −1 is attributed to Si-O stretching vibrations from Si-O-Si [4,24]. The absorption band at 803 cm −1 indicates the stretching vibration of O-H and also the Si-O-Si symmetric stretching vibrations.…”

“…It is usually used for the manufacture of cement, clay diet, and bricks. From an economic point of view, the most promising and efficient use of these mineral resources is for the manufacture of adsorbents, filter powders, fillers and catalysts [3,4].…”

“…Usually, natural diatomite contains impurity of the mineral and organic compounds that block the pores and diminish its absorption capacity. Therefore, it is necessary to remove the impurities from diatomite (pores) by chemical and/or thermal treatment [3][4][5][7][8][9][10]. For chemical treatment acid agents/activators (sulfuric acid, hydrochloric acid, phosphorous acid, etc.)…”

Improving Fresh and End-Used Carbon Surface by Sunlight: A Step Forward in Sustainable Carbon Processing

“…In general, surface porosity could be obtained through either the top-down (porosity development through surface etching) or bottom-up approach (carbon growth on a porous template). − In this case, a top-down surface treatment would be an ideal approach. Surface modification was reported on numerous occasions as an additional step to further enhance the surface adsorption performance. − The activation process (both physical and chemical routes) was widely adopted to enhance the surface area and porosity of the carbon. However, reactivating the recovered carbon at high temperature would result in further enlargement of pore size.…”

Production of hydrochar from corn silk by hydrothermal carbonization technique and its modification for more effective removal of Cr(VI)

“…Previous research has employed a variety of techniques to eliminate effectively Cr(VI) ions, including electrochemical, photocatalysis, chemical precipitation, bioremediation, filtration, ion exchange, and adsorption [12][13][14][15][16][17][18][19]. The adsorption approach is the most flexible of these.…”