Chitosan/modified montmorillonite beads and adsorption Reactive Red 120

摘要

Different molar mass (Mw) chitosans were prepared by the hydrolysis of commercial Mw 480,000 chitosan (CTS_(480)) with hydrogen peroxide at 4% (v/v) for 6 and 24 h and at 15% (v/v) for 24 h, yielding new smaller polymers of Mw 130,000 (CTS_(130)), 69,000 (CTS_(69)) and 14,000 (CTS_(14)), respectively. The four chitosan preparations were used to modify montmorillonite (MMT), but all only slightly increased the basal spacing. In contrast, intercalation of octadecylamine at a 2:5 (m/m) ratio of octadecylamine:MMT significantly increased the basal spacing. Therefore, octadecylamine was added to enhance the layer separation. The CTS_(69) chitosan preparation yielded the highest basal spacing. This mMMT (MMT:octadecylamine: CTS_(69) = 5:2:5 (m/m/m), respectively), was then used to prepare CTS_(480):mMMT composite beads with different mass ratios of CTS_(480) to mMMT, which were then evaluated as an adsorbent of Reactive Red 120. Three factors, (ⅰ) pH of dye solution in the range of 4-6, (ⅱ) increasing the mMMT ratio and (ⅲ) the amount of adsorbent to dye ratio, improved the adsorption efficiency. The adsorption isotherm of 1:1 (m/m) CTS_(480): mMMT composite beads agreed well with the Langmuir model.