title: Separation of toxic rhodamine B from aqueous solution using an efficient low-cost material, Azolla pinnata, by adsorption method.
abstract: This study investigated the potential of untreated Azolla pinnata (AP) to remove toxic rhodamine B (RB) dye. The effects of adsorbent dosage, pH, ionic strength, contact time, and concentration were studied. Experiments involving the effects of pH and ionic strength indicated that hydrophobic-hydrophobic interactions might be the dominant force of attraction for the RB-AP adsorption system. The kinetics modelling of the kinetics experiment showed that pseudo-second-order best represented the adsorption process. The Weber-Morris intraparticle diffusion model showed that intraparticle diffusion is not the rate-limiting step, while the Boyd model suggested that film diffusion might be rate-limiting. The adsorption isotherm model, Langmuir, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 72.2 and 199.7 mg g(-1) at 25 and 65 °C, respectively. Thermodynamics study indicates spontaneity, endothermic and physisorption-dominant adsorption process. The adsorbents were regenerated to satisfactory level with distilled water, HNO3 and NaOH. Pre-treatment of adsorbent with oxalic acid, citric acid, NaOH, HCl and phosphoric acid was investigated but the adsorption capacity was less than the untreated AP.
authors.affiliation: Chemical Sciences Programme, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Pengkalan Gadong, Bandar Seri Begawan, 1410, Brunei Darussalam. chernyuan@hotmail.com.
authors.forename: Muhammad Raziq Rahimi
authors.identifier: http://orcid.org/0000-0001-7974-3162
authors.initials: MR
authors.lastname: Kooh
authors.affiliation: Chemical Sciences Programme, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Pengkalan Gadong, Bandar Seri Begawan, 1410, Brunei Darussalam. linda.lim@ubd.edu.bn.
authors.forename: Linda B L
authors.initials: LB
authors.lastname: Lim
authors.affiliation: Chemical Sciences Programme, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Pengkalan Gadong, Bandar Seri Begawan, 1410, Brunei Darussalam. leehoon.lim@ubd.edu.bn.
authors.forename: Lee Hoon
authors.initials: LH
authors.lastname: Lim
authors.affiliation: Chemical Sciences Programme, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Pengkalan Gadong, Bandar Seri Begawan, 1410, Brunei Darussalam. kiddri86@hotmail.com.
authors.forename: Muhammad Khairud
authors.initials: MK
authors.lastname: Dahri
mesh_terms: D000327:Adsorption; D004058:Diffusion; D029624:Ferns / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D012235:Rhodamines / Q000032:analysis*; D013816:Thermodynamics; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D012235:Rhodamines; D014874:Water Pollutants, Chemical; C029773:rhodamine B
keywords: Adsorption isotherm; Azolla pinnata; Kinetics; Rhodamine B dye; Thermodynamics