###### Abstract  
This research focused on the removal of Fe(III) ions from an aqueous solution of wastewater through an adsorption process using biosorbents of natural palmyra palm fruit fibres (N-PPF) and chemically modified palmyra palm fruit fibres (C-PPF). BET was used to determine the pore volume and pore size of the biosorbents; the C-PPF was more than N-PPF at 0.01069 cm\({}^{3}\)/g and 450.2094 A, respectively. The initial concentration of Fe(III), the adsorbent dosage, solution pH, and contact time for optimal adsorption were investigated for adsorption, and it was found that the dosage of the adsorbent was 2.0 g, pH 4, and 300 min for adsorbent dosage, solution pH, and contact time, respectively. The adsorption data were consistent with the three models, though the Freundlich model provided the best fit. The characteristics for both before/after adsorption were examined by FT-IR, which showed that hydroxyl groups were involved in adsorption. SEM-EDX analysis confirmed the successful increase of containing functional groups during adsorption. Adsorption proceeded according to a pseudo-first-order kinetic model for N-PPF, while the adsorption of C-PPF was according to both kinetic models. It was revealed that Fe(III) adsorption is an exothermic process that occurs on the surface of heterogeneous adsorbents and physisorption. The intra-particle diffusion model is appropriate to explain the rate-controlling step in the Fe(III) adsorption process of natural fibres. adsorption; isotherm; kinetic; palmyra palm fruit; biosorbent +
Footnote †: journal: Medical  
can be harmful [3; 5]. Iron ions that are in heavy metals can cause serious problems in the environment, humans and animals, including diarrhoea, anorexia, metabolic acidosis, hypothermia, oliguria, diphasic shock, and even death [6]. In addition, receiving a large amount of iron will cause acute toxicity to the liver, kidney, heart, brain, spleen, adrenal glands and thymus gland, and the iron storage of the liver can become cirrhotic and become cancer of the liver [5; 7]. Thus, the World Health Organisation and the Thai Ministry of Public Health has set a guideline for iron intake in drinking water at 0.3 mg/L [8]. However, successful decontamination of heavy-metal-containing water through treatment is extremely difficult. The chemical precipitation/coagulation, ion exchange, solvent extraction, electrolysis and adsorption are currently being used for pollutant removal from aqueous medium [3; 4; 9; 10; 11]. Adsorption is a wastewater treatment method in which pollutants, such as ions, atoms, and molecules, are removed onto the surface of adsorbents. Because of its low cost, adsorption has become the most commonly utilised technology. However, commercial adsorbent materials are exorbitantly expensive. Therefore, they tend to only be used in limited circumstances [5; 6; 7]. Many studies have concentrated on the use of natural sorbents as an alternative to conventional ones, taking into consideration both environmental and economic concerns. Previously, activated carbon was typically utilised as an adsorbent, despite the fact that it was more expensive than alternative materials. Since then, a significant amount of studies have been performed on the use of low-cost agricultural products and byproducts as adsorbents for heavy metal removal. Fruit peels, peat, rice husk, sawdust, sugar beet pulp, and soya bean hulls have been found to be effective agricultural waste adsorbents. Furthermore, related minerals outperformed other adsorbents developed utilising physical and chemical methods for the removal of heavy metals [8; 9; 10; 11; 12; 13; 14]. The major elements of agricultural waste are lignin and cellulose, although it also contains hemicellulose, fatty sugars, starches, water, hydrocarbons, ash, and other substances. When left untreated, agricultural waste is a biosorbent, which can impact a number of problems, including low adsorption capacity, increased chemical oxygen demand, and biological oxygen demand [15; 16; 17].