Abstract
Powdered form of bones of silver carp fish, an available species in Bangladesh, was investigated as a prominent bioadsorbent for the removal of Congo red from synthetic solution. Experiments were conducted in batch process, and a number of influencing parameters, such as solution pH, adsorbent dosage, contact time, and initial Congo red concentration, were thoroughly investigated for optimization. Kinetic and equilibrium data were well described by pseudo-second-order model and Langmuir isotherm, respectively. Suitability of pseudo-second-order model to best fit with the adsorption process was corroborated by squared sum of errors analysis. Mass transfer mechanism was confirmed by intraparticle pore diffusion and Bangham’s diffusion models. Maximum sorption capacity of fish bone powder was found to be 666.67 mg·g−1. The optimum condition (adsorbent dose: 5 g·L−1; pH: 2.0; operating time: 4 h) for maximum sorption was determined as well. The increasing negative value of Gibbs free energy (ΔG) with temperature rise indicated spontaneous nature and feasibility of adsorption. The positive values of ΔH and ΔS suggested that the adsorption reaction is endothermic and random (at the solid/liquid interface) in nature. The activation energy (29.84 kJ·mol−1) indicated that the sorption process was of physisorption type. A considerably high adsorption capacity pointed towards utilization of this apparently useless biomaterial as an effective adsorbent.
Highlights
Industries, such as textile, leather, pulp and paper, cotton, paint, plastic, and cosmetics, use dyes to color their products and consume substantially a large volume of synthetic dye as well as process water for their production
General Characterization. e bulk density of the fish bone powder was measured to be 0.67 g·cm−3. e moisture content and the ash content of the adsorbent were found to be 3.1% and 36%, respectively. e pH of the adsorbent was determined by mixing fish bone powder with distilled water, and the value of pH was found as 7.8
Determination of pHpzc. e pH of the point of zero charge is an important parameter that gives idea to understanding the surface chemistry of an adsorbent. It is one of the essential physicochemical parameters that indicate the net charge of an adsorbent when it comes in contact with water [27]. It is defined as pH of the solution at which the surface charge of the adsorbent has zero value. e global surface charge of the adsorbent is negative at pH higher than pHpzc and positive at pH lower than pHpzc
Summary
Industries, such as textile, leather, pulp and paper, cotton, paint, plastic, and cosmetics, use dyes to color their products and consume substantially a large volume of synthetic dye as well as process water for their production. A different study was conducted for the removal of methylene blue dye from the wastewater using NaOH modified fish bone charcoal as adsorbent where the extent of sorption capacity was reported to be 605.82 ± 9.09 mg·g−1 [19]. The influence of several essential operating parameters (e.g., solution pH, dosages of adsorbent, initial concentration of adsorbate, and contact time) on Congo red removal using fish bone powder (FBP) adsorbent was investigated.
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