Optimized preparation of activated carbon from municipal sewage sludge and application to the adsorption of azo dye from aqueous solutions

Abstract

In this study, the conditions for preparation of active carbon from municipal sewage sludge (MSS) were optimized from application to the efficient removal of the azo dye, Acid Orange 7 (AO7), from aqueous solutions. To maximize the adsorption capacity (response variable) of the MSS‐derived activated carbon (MSS‐AC), a 3 k Box–Behnken design based on response surface methodology was used to simultaneously optimize five important conditions (independent variables), that is, carbonizing temperature (400–600°C), carbonizing time (0.5–2.0 h), impregnation ratio (1.0–3.5 g KOH/g MSS), activating temperature (600–800°C), and activating time (0.5–2.0 h). The optimal conditions were established as carbonizing temperature: 509°C, carbonizing time: 1.25 h, impregnation ratio: 2.3 g KOH/g MSS, activating temperature: 681°C, and activating time: 1.21 h, with an overall desirability function of 0.991. Further, the effects of various key parameters (solution pH, ionic strength, adsorbent dosage, initial concentration, contact time, and temperature) on the adsorption of AO7 on the as‐synthesized MSS‐AC were elucidated through a series of batch experiments. Adsorption kinetics and isotherm studies revealed that the adsorption process is accurately described by the pseudo‐second order and Sips models. The theoretical maximum adsorption capacity of AO7 was found to be ~1410 mg/g at 25°C, which is superior to that of the other adsorbents reported to date. Additionally, the intraparticle diffusion model suggested that the adsorption was controlled by both external surface adsorption and intraparticle diffusion. Thermodynamic studies also suggested that the adsorption of AO7 by MASS‐AC is exothermic and is governed by physisorption. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S267–S276, 2019

Synthesis and performance evaluation of adsorbents derived from sewage sludge blended with waste coal for nitrate and methyl red removal

“…Adsorption capacity decreased at pH6 from 97.488mg/g for DC-5-750M1 and 109.278 for DC-7-900M1 to 81.854 mg/g for DC-5-750M1 and 71.028 mg/g for DC-7-900M1. The results show that for the oxidized adsorbent at pH4 the adsorption mechanism was related to electrostatic attraction and hydrophobic associated to/or hydrogen bond 54 . Similarly, the adsorption potential of unoxidized SBAC (DC-5-750 and DC-7-900) decreased from 123.868 mg/g and 111.76 mg/g at pH 2 to 81.854 mg/g and 90.32 mg/g at pH 10.…”

Adsorption of Cr(VI) ions from aqueous solution using rice husk–based activated carbon: Optimization, kinetic, and thermodynamic studies

“…The F value and P value (Prob. > F ) were used to evaluate the statistical significance of the model as suggested by various earlier studies (Jung, Lee, & Lee, 2019; Sulaiman et al., 2018). The model F value of 202.13 and P < 0.001 in Table 3 imply that the model is significant for the removal of chromium ions.…”

Bio-Adsorbent Derived from Sewage Sludge Blended with Waste Coal for Nitrate and Methyl Red Removal: Synthesis, Oxidation, Performance and Environmental Consideration

“…The published data are also compared to the present study's nitrate adsorption capacities in Table 12.To assess the effect of ionic strength, MR was diluted in NaCl solution with a concentration of 0.01 M and 0,05M and the pH was adjusted at 4. As shown in Figure 23, presumably Na + cations competition and screening effect of Clanions at the external surface of adsorbent [54]…”

“…show that for the oxidized adsorbent at pH4 the adsorption mechanism was related to electrostatic attraction and hydrophobic associated to/or hydrogen bond [54]. Similarly, the adsorption potential of unoxidized SBAC (DC-5-750 and DC-7-900) decreased from 123,868 mg/g and 111,76 mg/g at pH 2 to 81,854 mg/g and 90,32 mg/g at pH 10.…”