Adsorption of Basic and Acid Dyes Using Alginate/Sericin Composite Beads

Abstract

INTRODUCTIONSynthetic dyes such as cationic (all basic dyes) and anionic (direct, acid and reactive dyes) were found to be present in wastewater from industries such as textile, leather, paper, printing, plastic, cosmetics and other. This dye pollutant has become a mojor source of contamination which is toxic and has detrimental effect on human health [1,2]. Moreover, the dyes pollutants were determinant hindering photosynthesis effects on ecosystem [3]. As a result the removal of the dye from the wastewater is essential. The methods of dye removal from wastewater, include membrane filtration [4], coagulationflocculation [5], advanced oxidation process [6], biodegradation [7], adsorption process [8] and ion exchange [9].The adsorption process is considered to be very effective for the removal of dye from wastewaters. Activated carbons from natural wastes are a great adsorbent due to low-cost materials, waste materials and by-products [10,11]. However, there are many problems regarding the regeneration of the exhausted activated carbon [12]. Thus, an effort has been made to develop them by using adsorbent materials such as: polymers, clays [13] Alginate/sericin composite beads were prepared from a blend between sericin and alginate by the gelation process. The composite beads were used as the adsorbent for the removal of basic and acid dyes from an aqueous solution. The morphological structure of the beads was characterized by scanning electron microscopy (SEM). Adsorption experiments were conducted using contact time, concentration of sericin, pH and adsorbent dosage. The equilibrium adsorption data was achieved within 360 min at 5 % w/v of sericin. The Langmuir isotherm model showed the maximum monolayer adsorption capacity for basic dye (pH 8) and acid dye (pH 2) was 5.98 and 7.60 mg/g, respectively. The adsorption kinetics were described by the pseudo second-order model. The desorption experiment was demonstrated and repeated three times, all of which exhibited that it was regenerative and reusable. This study demonstrates that the alginate/sericin composite beads are effective adsorbent for the removal of dyes from aqueous solution.