Chitosan/modified montmorillonite beads and adsorption Reactive Red 120

Different molar mass ( M w ― ) chitosans were prepared by the hydrolysis of commercial M w ― 480,000 chitosan (CTS480) 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 M w ― 130,000 (CTS130), 69,000 (CTS69) and 14,000 (CTS14), 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 CTS69 chitosan preparation yielded the highest basal spacing. This mMMT (MMT:octadecylamine: CTS69 = 5:2:5 (m/m/m), respectively), was then used to prepare CTS480:mMMT composite beads with different mass ratios of CTS480 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) CTS480: mMMT composite beads agreed well with the Langmuir model.