Effective removal of nitrate and phosphate anions from aqueous solutions using functionalised chitosan beads

Abstract

A B S T R A C TAdsorption of nitrate and phosphate from aqueous solution on both the protonated crosslinked chitosan beads (PCB) and carboxylated cross-linked chitosan beads (CCB) was investigated in batch mode. Effects of various parameters such as contact time, dosage of adsorbent, pH of the aqueous solutions, competitive co-anions and temperature on the sorption capacity of the sorbents were studied. The reuse of sorbents was evaluated by sequential sorptiondesorption cycles using 0.1 M NaOH as regenerant. Three isotherms namely Langmuir, Freundlich and Dubinin-Radushkevich were used to fit the equilibrium data, whereas the pseudo-second-order equation was used for the kinetic data. The E values obtained from the D-R isotherm at 303 K for nitrate and phosphate adsorption on PCB were 0.036 and 0.107 kJ/ mol, respectively, and on CCB were 0.029 and 0.114 kJ/mol, respectively, which confirms the physical adsorption between the anions and functional moieties in PCB and CCB. DH˚values revealed that the adsorption of nitrate is exothermic process and adsorption of phosphate is endothermic process. The sorbents were characterised by SEM and FTIR.

Chemically modified biochar produced from conocarpus waste increases NO3 removal from aqueous solutions

“…For example, biological methods are relatively slow and inefficient, and they generate excessive biomass (Kassaee et al 2011); reverse osmosis and electrocatalysis need costly installations and maintenance (Rodríguez-Marotoet et al 2009). Compared with these techniques, adsorption is reported to be one of the simplest and most efficient and economical techniques for removing NO 3 from water (Sowmya and Meenakshi 2014). Materials such as organo-clay, red mud, nanoalumina, ferric hydroxide and activated carbon have been widely examined as sorbents for NO 3 removal from aqueous media (Bagherifam et al 2014).…”

Adsorption of phosphate from aqueous solution by Zr(IV)‐crosslinked quaternized chitosan/bentonite composite

“…Moreover, the peak of 1379 cm 21 (C-H bending vibration) was dramatically weakened and even disappeared. A slight broadening at 1070 cm 21 was observed due to the presence of phosphate [32,33]. Besides, the intensities of the peaks between 520 and 1100 cm 21 reduced, which may be the result of the interactions between phosphate ions and BT(or Zr-OH) such as hydrogen bond and ligand exchange [6,34].…”

Removal of phosphate ions from wastewater by treated hydrogel based on chitosan

“…Since phosphate can exist in the form of H 3 PO 4 at pH less than 2, H 2 PO 4 at pH ranged between 2-7, HPO 4 2at pH ranged between 7-12.5 and PO 4 3at pH higher than 12.5 [28]. With increasing pH from 2 up to 6 more di-hydrogen phosphate (H 2 PO 4 -) existed in the solution which electro-statically attracted on the positive sites of -NH 3 + , -NH 2 + (CH 3 ) 2 , -SH 2 + and-Si-O + H 2 on the surface of adsorbents [29][30][31]. The surface charge of CS is positive in acidic medium, gradually decreases with increasing in pH up to the zero point of charge at pH 6.4 [32].…”