Magnetic rice husk ash 'cleanser' as efficient methylene blue adsorbent

Abstract

Burning of agricultural residues has been a prevalent cause of environmental concern especially in developing countries. In the Philippines, rice husks are usually burned in open air and either usually left in the field or rarely collected to be sold in the wet market as a cleanser. Hence in this study, an alternative use of this burning residue (rice husks ash, RHA) for removal of dyes from aqueous solutions was explored. Yet, its applications in real wastewater will be difficult in its pristine powdered form. Therefore, the RHA was functionalized with Fe<sub>3</sub>O<sub>4</sub> to become inherently magnetic (MRHA), providing relative ease in handling. The RHA used was obtained from the local markets of Davao City, Philippines. Systematic adsorption studies on the effects of contact time, solution pH, solid/liquid ratio, and feed concentration were conducted. MB adsorption was Langmuir-type and followed a pseudo-second-order rate model. Its adsorption rate is significantly fast (<i>t</i> = 10 min, <i>k</i><sub>2</sub> = 0.015 g mg<sup>-1</sup> min<sup>-1</sup>) with high <i>q<sub>m</sub></i> (150.5 mg g<sup>-1</sup>). MRHA was highly stable and reusable (> 10 cycles) demonstrating its high potential as an economical alternative for treatment of dye contaminated wastewater.

Preparation of magnetic mesoporous silica from rice husk for aflatoxin B1 removal: Optimum process and adsorption mechanism

“…The peaks at 1232, 1088, 800, and 462 cm −1 were assigned to Si–O stretching and bending vibrations. The peaks at 972 and 1635 cm −1 corresponded to bending vibrations for Si-OH groups [ 26 ]. The peak near 559 cm −1 could be attributed to Fe–O stretching vibration, indicating the presence of Fe 3 O 4 [ 17 ], in agreement with the findings of Zahoor [ 41 , 42 ] and the XRD results.…”

“…The unit adsorption capacity and AFB1 adsorption rate were determined after adsorption times of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.5 h. According to the results, quasi-first-order and quasi-second-order kinetic models were used for fitting to obtain the relationship between the reaction time and the sample adsorption capacity, and to analyze possible adsorption behavior. The specific model formulae are as follows [ 26 ]: where q t is the amount of AFB1 adsorbed after reaction time t (mg/g), k 1 is the rate constant for the quasi-first-order kinetic reaction (min −1 ), and k 2 is the rate constant for the quasi-second-order kinetic reaction (g/(mg·min)).…”

“…The unit adsorption capacity and AFB1 adsorption rate were determined after adsorption times of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.5 h. According to the results, quasi-first-order and quasi-second-order kinetic models were used for fitting to obtain the relationship between the reaction time and the sample adsorption capacity, and to analyze possible adsorption behavior. The specific model formulae are as follows [26]:…”

“…This paper focused on MMS from rice husk ash for removal of AFB1 in oil, compared with other similar studies. Furthermore, this magnetic mesoporous material can be applied for removal of mycotoxins (AFB1 [41] and ochratoxin A [21]), toxic metals (Hg [19], Cd 2+ [52], Cu, and Co [53]), dyes (methyl blue [25,26]), pesticides (pyrethroid [54]), pharmaceuticals (minocycline [17]), and other emerging pollutants [40], and may be suitable for drug delivery [55] in the future.…”

“…MS material (R-MCM) made from rice husk ash had a surface area of 1347 m 2 /g, a pore volume of 0.906 cm 3 /g, and a maximum removal efficiency for methyl blue of 99% [ 25 ]. The rate of methyl blue adsorption on magnetic material (MRHA) made from Fe 3 O 4 and functionalized rice-husk ash was high, with a high q m (150.5 mg/g) [ 26 ]. Sodium silicate solution extracted from rice husk has been used to synthesize various MS materials with a specific pore structure (mesocellular forms and hexagonal nanochannel structures), pore size (3–60 nm), surface area (297–895 m 2 /g), and pore volume (0.81–1.77 cm 3 /g) [ 27 ].…”