Novel chitosan/citric acid modified pistachio shell/halloysite nanotubes cross-linked by glutaraldehyde biocomposite beads applied to methylene blue removal

Abstract

In this study, Cht/PS-CA/HNT biocomposite adsorbent was synthesized using halloysite nanotube as nanomaterial, chitosan which is a biodegradable and biocompatible biopolymer, pistachio shell as biomass source, citric acid as biomass modifier. The removal of methylene blue dyestuff on the synthesized new Cht/PS-CA/HNT from the aqueous medium by adsorption method was investigated. Experimental parameters such as dye concentration, contact time, amount of adsorbent, solution pH and temperature, which affect the adsorption process, were investigated. The adsorption experimental data were analyzed with the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms, which are widely used in aqueous solutions, and it was decided that Langmuir is the most suitable isotherm. The maximum adsorption capacity of the monolayer was calculated to be 111.14 mg/g. Optimum contact time and adsorbent dose were determined as 90 min and 1 g/L. Adsorption experimental data were applied for Pseudo-first-order and Pseudo-second-order kinetic models and it was decided that the most suitable kinetic model was pseudo-second-order. Thermodynamic evaluation of adsorption showed that adsorption is endothermic and adsorption is spontaneous. NOVELTY STATEMENTIn the present study, it was determined that chitosan beads prepared using citric acid modified pistachio shells and HNT have strong adsorption properties for dyestuff removal, which is one of the important causes of environmental pollution. The novelty of this work is based on the development of a new composite adsorbent that can be synthesized in a simple and fast method and does not require expensive reagents or complex equipment. Another innovation is that MB dyestuff, which has a highly harmful effect, can be easily removed from polluted water by using simple biowaste-based adsorbents by adopting appropriate procedures.