Adsorption of methylene blue onto carbons made of residues from the biodiesel industry

Abstract

The performance of carbons produced from the cold-pressed cake of Raphanus sativus (L. var.), a residue from the biodiesel industry, was evaluated for the adsorption of methylene blue (MB) from synthetic aqueous solutions. The study has focused on the following three topics: (i) physical and textural characterization of the carbon, (ii) batch investigation of equilibrium and kinetics of MB adsorption at room temperature, and (iii) analysis of MB adsorption mechanism onto such carbonaceous structures. Regarding the fi rst topic, carbon was characterized using several methods such as Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), scanning electron microscopy (SEM), and Raman spectroscopy. A microporous carbon was found thus indicating that MB adsorption may occur predominantly at the surface of the carbon. Regarding the second topic, equilibrium tests revealed that Langmuir-based maximum MB uptake capacity was 19.8 mg g -1 and that MB kinetics onto carbon was best described by a pseudo second-order model. Data fi tting analysis confi rmed that MB adsorption onto such carbons was predominantly superfi cial. And fi nally, regarding the third topic, MB adsorption may probably occur by bonding of monomer MB through the central nitrogen atom of its molecule and through sulfur atom while MB bonding through amino nitrogen atom does not seem probable. The study reveals that carbons made of R. sativus are suitable materials for the removal of dyes from aqueous solutions, mainly if fi ner fraction of carbons is used, because MB adsorption was found to be predominantly superfi cial.

Comparative Evaluation of Acid and Basic Thermo-Chemical Treatments in the Production of Adsorbents Based on Biodiesel Production Solid Residue

“…Notice that microwave activation provided a significant increase in adsorption capacity in the case of the adsorbent prepared with KOH (A5 vs. A6). A similar behavior was reported in the literature, employing adsorbents based on both Raphanus sativus and other types of press cakes, but without any chemical activation [1], [6]- [8].…”

“…Future studies will be focused on evaluation of such adsorbent for removal of other types of polutants (organics, heavy metals) and also on fixed-bed tests aiming at industrial applications. Defective coffee beans oven 14.9 [6] Defective coffee beans microwave 68.5 [7] Raphanus sativus oven 18.3 [8] Sunflower seeds oven/ H2SO4 16.4 [13] Other materials Sugarcane bagass EDTA 202 [23] where K F is a constant that indicates the relative adsorption capacity (mg 1-(1/n) L 1/n g −1 ) and n is related to the intensity of adsorption [18]. (10) …”

“…These solid residues present environmental problems in terms of adequate disposal, given their limited applications as animal feed, silage or energy source, thus reinforcing the need for alternative uses. A few recent studies have shown that this type of residue (oilseed press-cakes from biodiesel production) can be used for AC production [1], [6]- [8].…”

“…In view of the aforementioned, and taking into account that the studies available in the literature on the use of RS press-cakes for production of adsorbents did not involve chemical activation [1], [8], the objective of this study was to compare thermo-chemical treatments in the production of adsorbents for dye removal. Both acid and basic activated agents were employed, as well as conventional and microwave carbonization.…”

Pollutant Soot for Pollutant Dye Degradation: Soluble Graphene Nanosheets for Visible Light Induced Photodegradation of Methylene Blue

“…Raman spectra of MB as shown in Figure b-i shows the most intense band at 1623 cm –1 which is assigned to sp 2 hybridized aromatic υ­(C–C) ring stretching . Furthermore, two neighboring bands at 1394 cm –1 and 1439 cm –1 corresponds to υ sym (C–N) stretching and υ asym (C–N) stretching, respectively . Likewise in the same panel wsGNS (Figure b-ii) shows the characteristic disordered (D-band) and graphitic (G-band) at 1337 and 1566 cm –1 , respectively.…”