Improving the Adsorption Performance of Loofah Sponge towards Methylene Blue by Coating Ca2+ Crosslinked Sodium Alginate Layers on Its Fiber Surface

In this study, natural polymer sodium alginate (SA) was covered with high active carboxyl groups on the loofah sponge (LS) fiber surface to improve the adsorption ability of LS. The SA was covered on the LS fiber surface (LS@SA) through simple soaking in SA solution and then in situ hardening in Ca2+ solution. The influence of SA consistency on the SA loading ratio was estimated. The obtained LS@SA adsorbents were employed to absorb methylene blue (MB) from the water. The effects of various experimental parameters on the adsorption capacity of the LS@SA adsorbents were studied using a batch adsorption technique. Results indicated that the SA was successfully covered on the LS fiber surface and the SA loading rate increased with increasing SA concentration. The SA layer covering the LS fiber surface provided the LS@SA adsorbents with higher adsorption capacity towards MB than the original LS due to the high density of carboxyl groups on the SA molecular chain. In the adsorption process, the LS@SA adsorbents were pH dependent. The results also indicate that the LS@SA adsorbents have better reusability.