Development of fast and high-efficiency sponge-gourd fibers (Luffa cylindrica)/hydroxyapatite composites for removal of lead and methylene blue

Oxidized-fibers, cellulose, and oxidized-nanocellulose were isolated from sponge-gourd fibers (Luffa cylindrica) and used as natural, non-toxic, and low-cost adsorbents. The effect of three luffa forms with or without hydroxyapatite (HAp) on the removal efficiency of lead ions (Pb2+) and methylene blue (MB) was investigated. HAp was successfully synthesized on the surface of Luffa with an average length of 40-56 nm and a width of 14-19 nm. Prepared materials showed differences in morphology (shape and size), chemical structure, and crystalline properties. The effect of sorbent type, contact time, and initial MB and Pb2+ concentrations were studied. The results showed that luffa/HAp composites were more effective in removal of Pb2+ ions than MB compared to Luffa without HAp, and vice versa. Kinetic and adsorption studies of MB and Pb2+ ions were well fitted with the pseudo-second-order and Langmuir models. The maximum adsorption capacity of Pb2+ was 625 mg/g, 714 mg/g, and 714.5 mg/g for oxidized-fibers/HAp, oxidized-nanocellulose/HAp, and cellulose/HAp, respectively, at dose 4 g/L, pH 5.3, 25 degrees C. While the maximum adsorption capacity of MB was 25.2 mg/g, 30.8 mg/g, and 36.2 mg/g for oxidized-fibers/HAp, oxidized-fibers, and cellulose, respectively, at dose 4 g/L, pH 7.3, 25 degrees C. Also, more than 95% of lead (500 mg/L) and 85% of MB (25 mg/L) were removed within the first 5 min. Separately, cellulose sample was the most effective in removing MB while cellulose/HAp for removal of Pb2+. However, oxidized-fibers/HAp composite was the easiest to prepare and the most effective in removing both MB and Pb2+. (C) 2021 The Authors. Published by Elsevier B.V. on behalf of King Saud University.

Automated summary

The study found that luffa fiber composites synthesized with HAp were more effective in removing Pb2+ ions, while cellulose was more efficient in removing MB.