Piyamongkala, kowit, and วัจนะรัตน์ พิมพ์ชยา. 2017. “Adsorption of copper and lead ions by chitosan powder and sodium tripolyphosphate-modified chitosan resin: Kinetics, mechanism and mass transfer”. Naresuan University Engineering Journal 12 (1). Phitsanulok, Thailand:83-96. https://doi.org/10.14456/nuej.2017.4.