Quaternary phosphonium modification of esterified sugar beet pulp with maleic anhydride and its biosorption property on anionic and cationic dyes

To improve the adsorption capacity of SBP, an idea of adding the functional carboxylic groups using multivariant organic acids was raised and tried. Quaternary phosphonium bromide and maleic anhydride modified sugar beet pulp (PMSBP) was prepared by quaternary phosphonium modification on the basis of maleic anhydride-modified sugar beet pulp (MSBP). Characterization results showed that the thermal stability of PMSBP was improved compared to MSBP, and the surface of PMSBP showed uniform layered structure with large pores. The effects of temperature, reaction time, pH, and adsorbent dosage on the adsorption of two dyes by PMSBP were investigated. The adsorption of PMSBP on methyl orange (MO) fitted well with the Langmuir isotherm model and the pseudo-second-order kinetic model, and the Freundlich isotherm model could better describe the adsorption process of PMSBP on methylene blue (MB). The adsorption of MB and MO by PMSBP was exothermic and spontaneous. PMSBP was demonstrated to satisfy the essential requirement for application in wastewater treatment. Electrostatic attraction and ion exchange were speculated as the main adsorption mechanisms. So, the broom modification theory of bio-sorbents was practical and offered a way to improve bio-sorbents adsorption capacity.