Abstract
Methylene blue (MB) is the cationic dye that is widely used for coloring cotton, wool, and silk. Since MB is harmful to human beings and toxic to microorganisms, there is the need to find cheap and efficient methods for removal of MB from wastewater prior to disposal into natural waters. In the present study, MB adsorption potential of MgO/AC prepared using a sol-gel-thermal deep-coating method was compared with the activated carbon (AC). The central composite design (CCD) as a method of the response surface methodology (RSM) was applied to minimize the number of runs and process optimization. The characterization of the microporous MgO/AC composite showed that the magnesium oxide nanoparticles were successfully coated on the AC and the BET specific surface area of AC and MgO/AC were 1,540 and 1,246 m2/g, respectively. The MB removal efficiency and the maximum adsorption capacity of AC and MgO/AC were 89.6, 97.5% and 571.7, 642.3 mg/g, respectively under optimum operational conditions of initial dye concentration of 100.9 mg/L, the adsorbent dosage of 69.4 mg/100 mL, pH of 10.2 and contact time of 149.1 min. According to an analysis of variance (ANOVA), the initial dye concentration and its interaction with the other effective factors have a large impact on adsorption efficiency. Furthermore, the mechanism of adsorption followed the Langmuir isotherm (R2 = 0.9935, Δqe = 2.9%) and adsorption kinetics fitted by the pseudo-second-order model (R2 = 0.9967, Δqe = 6.6%). Finally, our results suggest that the prepared MgO/AC is an efficient and promising material for dye wastewater treatment.
Highlights
Dyes and pigments are released into wastewaters from various industrial units, mainly from the dyestuffs, textile, paper, and plastics (Crini )
The bulk density was less than 1.2 (0.5 g/ mL) (Table 1) indicating that the activated carbon materials are fine in nature and enhanced the adsorption of Methylene blue (MB) from aqueous solution (Moyo et al )
The experimental qe values agreed with the calculated values obtained from the no linear plots (Figure 6). In this investigation, activated carbon was coated with magnesium oxide nanoparticles using the sol–gel-thermal deepcoating method and used as an efficient adsorbent for the removal of methylene blue
Summary
Dyes and pigments are released into wastewaters from various industrial units, mainly from the dyestuffs, textile, paper, and plastics (Crini ). These dyes are primarily of synthetic origin and have complex aromatic structures, which make them more stable to light, heat and oxidizing agents, and are usually biologically non-degradable (Wang et al ). Several non-conventional, low-cost adsorbents have been tested for dye removal. These include activated sludge, coir pith, minerals, neem leaf, peat, red mud, tree fern, and waste organic peel (Lorenc-Grabowska & Gryglewicz ). Activated carbons, prepared from agricultural materials, had good adsorption capacities for heavy metals, phenol, and dyes (Ioannidou & Zabaniotou ; Belaid et al )
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