Abstract
Kapok fiber (Ceiba pentandra) belongs to a group of natural fibers that are mainly composed of cellulose, lignin, pectin, and small traces of inorganic compounds. These fibers are lightweight with hollow tubular structure that is easy to process and abundant in nature. Currently, kapok fibers are used in industry as filling material for beddings, upholstery, soft toys, and nonwoven materials. However, kapok fiber has also a potential application in the adsorptive removal of heavy metal ions and dyes from aqueous systems. This study aims to provide a comprehensive review about the recent developments on kapok fiber composites including its chemical properties, wettability, and surface morphology. Effective and innovative kapok fiber composites are analyzed with the help of characterization tools such as scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller analysis. Different pre-treatment methods such as alkali and acid pre-treatment, oxidation pre-treatment, and Fenton reaction are discussed. These techniques are applied to enhance the hydrophilicity and to generate rougher fiber surfaces. Moreover, surface modification and synthesis of kapok fiber-based composites and its environmental applications are examined. There are various methods in the fabrication of kapok fiber composites that include chemical modification and polymerization. These procedures allow the kapok fiber composites to have higher adsorption capacities for selective heavy metal and dye removal.
Highlights
Heavy metal ion and dye pollution caused by industrialization and urbanization has caused significant hazards to both environmental and human health [1,2]
Since adsorption processes occur in aqueous solutions, a hydrophilic surface is desirable in heavy metal and dye removal
The intensity in Fourier transform infrared (FTIR) spectra of the Fenton reaction was observed to decrease. This allows for the conversion of Kapok fiber (KF) from hydrophobic to hydrophilic, which enhances heavy metal ion adsorption capacity when hydroxyl, carboxyl, or aldehyde groups are added during the Fenton reaction
Summary
Heavy metal ion and dye pollution caused by industrialization and urbanization has caused significant hazards to both environmental and human health [1,2]. Dyes are classified as either synthetic or natural chemical substances that are used to provide color to numerous substrates such as waxes, leather, fur, plastics, cosmetics, greases, and textile materials [4,17] Because of their complex and large molecular structures, dye molecules remain in bodies of water for a long time, resisting degradation by natural mechanisms such as microbial interactions and sunlight [18]. Various methods have been developed to remove heavy metals and dyes from aqueous systems These methods include membrane filtration, chemical coagulation and flocculation, biological treatment, ion exchange, photocatalytic degradation, and adsorption. The specific objectives of the study are as follows: (1) to provide an in-depth review of the various pre-treatment methods and surface modifications applied to KF; (2) to evaluate the structure and properties of modified KF from various synthetic routes; and (3) to analyze of the adsorptive performance of the KF composites
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