More than 170 million individuals have been influenced by arsenic (As) because of the ingestion of As-polluted groundwater. The presence of As in water bodies, particularly groundwater, has been found to become a widespread issue in the past few decades. Because arsenic causes extreme wellbeing impacts, even at a low concentration in drinking water, the innovations of As removal from contaminated water are of significant importance. Traditional strategies, for example, reverse osmosis, ion exchange, and electro-dialysis are generally utilized for the remediation of As-polluted water; however, the high cost and/or sludge production restricts their application in less-developed areas. The utilization of adsorbents acquired from natural materials has been explored as an alternative for the costly techniques for As removal. This paper aims to review the past and current developments in using naturals adsorbents or modified natural materials for arsenic removal and show the different parameters, which may influence the As removal effectiveness of the natural adsorbent, such as contact time, adsorbent dosage, flow rate, pH, reusability, temperature, and influence of others ions.

The growth status, root exudates, radial oxygen loss, and sewage purification effect of plants acclimated with sewage and cultured with a nutrient solution were studied by selecting Acorus gramineus Aiton, Pistia stratiotes L., and Eichhornia crassipes (Mart.) Solms with the same individual size. The results showed that the root oxygen secretion rate of the Acorus gramineus Aiton was higher in light and dark conditions. For a single plant species, the oxygen secretion rate under light conditions was much higher than that under dark conditions. The root oxygen secretion rate of Acorus gramineus Aiton was the highest (2.03 µmol O₂/h/plant), followed by Pistia stratiotes L. (1.68 µmol O₂/h/plant), and the root oxygen secretion rate of Eichhornia crassipes (Mart.) Solms was the lowest (1.15 µmol O₂/h/plant). After a period of adaptation, plants showed strong removal effects on COD, NH₃-N, TN, and TP. The removal intensity was in the order of Acorus gramineus Aiton > Pistia stratiotes L. > Eichhornia crassipes (Mart.) Solms; the higher the temperature, the bigger the removal rate. These results were consistent with Acorus gramineus Aiton‘s organic matter secretion and radial oxygen loss, which were better than those of Pistia stratiotes L. and Eichhornia crassipes (Mart.) Solms. Three kinds of plants had better COD removal effects in an acidic environment and better TP removal effects in an alkaline environment. The results show that using the Acorus gramineus Aiton can achieve better remediation of polluted water bodies.

Arsenic in groundwater is a severe problem, especially in rural areas. This research developed a novel sorbent (Fe-kapok) by hydrothermal surface treatment of natural fibres with iron for As(V) removal from groundwater in a column-fixed bed. The Fe-kapok was extensively characterised using various high-technology instruments and methods. Results showed higher specific surface area BET (3.272 m²/g) and pore volume (0.032 cm³/g) for Fe-kapok than raw kapok (0.976 m²/g and 0.021 cm³/g), indicating its higher As(V) adsorption capacity. Fe-kapok was effective at As(V) adsorption despite the presence of competing ions, such as sulphate, with its high interference capacity in the groundwater. Nonetheless, the As(V) adsorption efficiency declined with increasing flow rate and As(V) initial concentration. By contrast, the As(V) removal efficiency increased with increasing adsorbent dosage and groundwater temperature, and the optimal adsorption was achieved at neutral pH. The Thomas model predicted an adsorption capacity of 6.63 mg.g⁻¹ at 25°C, 3 g adsorbent dose, and 100 µg.L⁻¹ As(V) concentration for Fe-kapok. However, the Bohart and Adams correlation coefficient (R² = 0.88–0.99) was higher than the Thomas R² (0.89–0.98). Regeneration and reusability of Fe-kapok were demonstrated after eight adsorption cycles, and it could run for up to 600 minutes before saturation at the last reuse round.