Enhanced Adsorption of Orange II Using Cationic Surfactant Modified Biochar Pyrolyzed from Cornstalk

Abstract

As dissolution of raw biomass is serious when used as an adsorbent, the cheap biochar pyrolyzed from biomass might be a good matrix. Raw cornstalk biochar was intentionally modified by cetyltrimethylammonium bromide (CTAB) to prepare the composite adsorbent designed for the removal of negatively charged pollutants. After modification, the removal efficiency for anionic dye Orange II (ORII) increased from 46.9% of the virgin cornstalk biochar to 99.7% of the CTAB-modified cornstalk biochar. The uptake of ORII proved to be favorable under acidic conditions but unfavorable under alkaline conditions. By nonlinear simulation, the Elovich model was the best to describe the adsorption kinetics. For linear simulation of the kinetic data, the pseudo-second-order kinetic model fitted the experimental points better than the pseudo-first-order model. Kinetic analysis indicated that the ORII adsorption process on the CTAB-modified cornstalk biochar might be chemical adsorption accompanied by ion exchange. At 298 K, the maximal adsorption capacity of the modified biochar is 26.9 mg/g by the Langmuir model. The adsorption of ORII increased with a rise in the reaction temperature. The enthalpy and entropy of the adsorption process are calculated to be 38.45 KJ mol−1and 185.0 J mol−1 K−1, respectively. The negative values ofΔG0at 288, 298, and 308 K were −14.92, −16.50, and −18.62 KJ mol−1, respectively. The above thermodynamic analysis demonstrates that the adsorption process was endothermic and spontaneous.

Adsorption of Reactive Dyes from Wastewater Using Cationic Surfactant-modified Coffee Husk Biochar

“…Here, C0 is the initial dye concentration (mg/L), Ct is the residual dye concentration in the solution after adsorption, V is the solution volume (L), and m is the mass of adsorbent (g) (Mi et al, 2016). Then, the adsorption kinetics was assessed against both pseudo-first order and pseudo-second order models.…”

“…The Langmuir model describes monolayer adsorption on a homogenous surface. The Freundlich model describes multilayer adsorption on a heterogeneous surface (Ibrahim et al, 2010;Ghazi Mokri et al, 2015;Mi et al, 2016). The Langmuir and Freundlich models are expressed in Equation 5and Equation (6), respectively:…”

“…The tails of CTAB adsorb on hydrophobic sites of the ACH surface through Van der Waals attraction forces (Krivova et al, 2013;Ahmad et al, 2014;Puasa et al, 2018). Additionally, the positively charged heads can effectively adsorb negatively charged RDY145 molecules from wastewater by electrostatic interactions (Mi et al, 2016;Puasa et al, 2018). Thus, the MCH modified with this cationic surfactant has potential for anionic dye removal from wastewater.…”

“…Nowadays, agricultural residues with high carbon content, such as palm shell, coconut coir, and rice husk have been studied as potential alternative adsorbents for AC (Sun et al, 2013;Ahmad et al, 2014;Mook et al, 2016;Mi et al, 2016). Typically, they can be applied to produce biochar by thermal degradation in oxygen-limited conditions, and consequently utilized as a low-cost adsorbent for pollutant separation from air, or heavy metals as well as textile dye removal from wastewater (Mi et al, 2016;Moazzam et al, 2017;Rehman and Razzaq, 2017). Biochar adsorption has been intensively studied because it has excellent adsorption capability and satisfies the need for cost effective adsorbents.…”

“…Besides, surface modification of the biochar with surfactants could enhance the adsorption capacity and ensure environmental friendliness (Puasa et al, 2018). Mi et al (2016) reported that biochar prepared from cornstalk and modified by Cetyltrimethylammonium bromide (CTAB) had up to 53% improved adsorption of negatively charged anionic dye from water. In addition, all the studies have agreed that using biochar as a precursor for AC for reactive dye removal provided a great adsorption performance, cheap treatment costs, no unexpected by-products, and minimal waste.…”