การดูดซับสีรีแอคทีฟและสีดิสเฟิร์สในน้ำเสียสังเคราะห์โดยใช้ถ่านเปลือกเมล็ดกาแฟที่ปรับปรุงสภาพด้วยสารลดแรงตึงผิวชนิดประจุบวก

Abstract

A solid agricultural waste, coffee husk, was applied as an adsorbent for reactive and disperse dye-polluted wastewater treatment. The coffee husk was pyrolyzed at 450°C and then chemically activated using 50 %wt ZnCl2 solution. The CH contains higher average pore size but slightly lower surface area than those of commercial activated carbon (AC). The CH was then modified using a cationic surfactant, Cetyltrimethylammonium bromide (CTAB), at 7.5 mM of initial CTAB concentration, pH 7 at 30°C, 170 rpm, and 7.5 h. The adsorption behaviors of CTAB on CH adsorbents suited well with the pseudo-second order adsorption kinetics and the Langmuir isotherm model. For dye removal, the experiment was divided into two parts. For part 1, the modified coffee husk biochar (MCH) was applied for reactive dyes removal. The selected reactive dyes are reactive yellow 145 (RDY145), reactive red 195 (RDR195), and reactive blue 222 (RDB222). The adsorption kinetics was fit well with the pseudo-second order for all three dyes. The adsorption isotherm was agreed well with the Langmuir isotherm model. The removal efficiency of RDY145 (83.796) was the highest and followed by RDR195 (71.1%) and RDB222 (59.6%), respectively. The adsorption of RDY145 using MCH was subsequently compared with AC and surfactant-modified activated carbon (MAC). It was found that the dye adsorption using MCH was higher than AC and MAC around 9 folds. For part 2, the MCH was applied for disperse dyes removal. The selected disperse dyes were disperse yellow 3 (DDY3), disperse red 60 (DDR60), and disperse blue 56 (DDB56). The removal efficiency of DDY3 (79.5 %) was the highest, followed by DDR6 (23.2 %), and DDB56 (9.7 %), respectively. The adsorption kinetics was fit well by a pseudo-first order model and the adsorption isotherms matched well the Freundlich model, for DDY3 and DDB56. Besides, the adsorption kinetics of DDR60 was fit well by a pseudo-second order model and the adsorption isotherms matched well the Langmuir model. In addition, the removal efficiency of DDY3 using MAC (85.8 %) was higher than AC (84.3 %) and MCH (79.5 %), respectively. The standard deviation was less than 10. To improve the adsorption of DDY3, the CH and AC were then modified using cationic (CTAB), anionic (Sodium dodecyl sulfate, SDS) or nonionic surfactant (Polyethylene glycol sorbitan monooleate, Tween 80). The hydrophilic head group of SDS is smaller than that of CTAB and Tween 80, respectively. It was found that the adsorption of DDY3 using SDS-modified was the highest, followed by those of CTAB-modified, and Tween 80-modified, respectively. The smaller hydrophilic head group provides the higher adsorption. Additionally, the adsorption efficiency of DDY3 using surfactant-modified CH was higher than those using AC for all conditions. Additionally, the variation of pH solution provided no effect on reactive and disperse dyes removal efficiency. Moreover, the dye removal using a fixed-bed column was preliminary studied and discussed. The adsorption of RDY145 and DDY3 using MCH, AC, and MAC were observed and compared. The column packed with MCH provided the highest RDY145 removal and that packed with AC provided the highest DDY3 removal.