Biosorption of Cr(III) from aqueous solution by freeze-dried activated sludge: Equilibrium, kinetic and thermodynamic studies

Abstract

Batch biosorption experiments were conducted to remove Cr(III) from aqueous solutions using activated sludge from a sewage treatment plant. An investigation was conducted on the effects of the initial pH, contact time, temperature, and initial Cr(III) concentration in the biosorption process. The results revealed that the activated sludge exhibited the highest Cr(III) uptake capacity (120 mg%g -1 ) at 45°C, initial pH of 4, and initial Cr(III) concentration of 100 mg%L -1 . The biosorption results obtained at various temperatures showed that the biosorption pattern accurately followed the Langmuir model. The calculated thermodynamic parameters, ΔG o ( -0.8--4.58 kJ%mol -1 ), ΔH o (15.6-44.4 kJ%mol -1 ), and ΔS o (0.06-0.15 kJ%mol -1 %K -1 ) clearly indicated that the biosorption process was feasible, spontaneous, endothermic, and physical. The pseudo first-order and second-order kinetic models were adopted to describe the experimental data, which revealed that the Cr(III) biosorption process conformed to the second-order rate expression and the biosorption rate constants decreased with increasing Cr (III) concentration. The analysis of the values of biosorption activation energy (E a = -7 kJ%mol -1 ) and the intraparticle diffusion model demonstrated that Cr(III) biosorption was film-diffusion-controlled.

Aqueous nitrate removal by D417 resin: thermodynamic, kinetic and response surface methodology studies

“…During the first 4 min 1/2 , adsorption was linear and characterized by extremely fast uptake, which should be attributed to the rapid use of the available active sites on the heterogeneous resin surfaces. In the second phase, the adsorption rate became slow but comparatively higher than that of others' studies, which might be attributed to multilayer adsorption in our study compared with monolayer adsorption reported by them. Moreover, a straight line with high regression coefficients ( R 2 = 0.9671) (as shown in Fig.…”

“…The enthalpy change (Δ H ) exhibited that the adsorption process was endothermic at C 0 = 5–10 mg·L −1 but turned to exothermic type when C 0 increased to 15–50 mg·L −1 . All values of Δ G were between 0 and −20 kJ·mol −1 , indicating that the adsorption processes had thermodynamic feasibility and spontaneous nature . The decrease tendency of Δ G with the increase of temperature was obvious under low initial concentrations.…”

“…and . Δ H and Δ S can be estimated from the slope and intercept of Van't Hoff plots of (ln C e – ln Q e ) vs 1/ T …”

Nanomaterial Transformation and Association with Fresh and Freeze-Dried Wastewater Activated Sludge: Implications for Testing Protocol and Environmental Fate

“…The United States Environmental Protection Agency (USEPA) provided a standard method for testing soluble pollutant sorption to activated sludge with the publication of the OPPTS 835.1110 Activated Sludge Sorption Isotherm test guideline . The experimental method outlined in this guideline has become standard industry and research practice for predicting chemical removal from wastewater during biological treatment in WWTPs. ,− OPPTS 835.1110 calls for the use of freeze-dried and heat-treated (FDH) activated sludge as sorbent. Unlike fresh activated sludge, which must be collected, processed, and used daily, FDH activated sludge can be stored for several months, allowing for a convenient and uniform supply of sorbent for batch experiments.…”

Kinetic modeling of the biosorption of Cd2+ ions from aqueous solutions onto Eichhornia crassipes roots using potentiometry: low-cost alternative to conventional methods

“…The curve obtained here included four separate regions (Figure 2b): an initial curved region (1) followed by two linear regions (2 and 3), and then a plateau (4). Several authors [14][15][16] have reported similar behavior and attributed the different regions of the curve to the sequential stages of solute mass transfer to the adsorbent. In region (1), film diffusion from the bulk solution to the sorbent surface constituted the main process.…”