An investigation on biosorption of nitrate from water by chitosan based organic-inorganic hybrid biocomposites

In this study, three types of crosslinked organic-inorganic hybrid biocomposites, such as chitosan/bentonite, chitosan/titanium oxide, and chitosan/alumina (ChBT, ChTi, and ChAl respectively) were prepared and utilized for the removal of nitrate from water by batch biosorption experiments. Effects of crosslinker dose, initial nitrate concentration, contact time, initial pH of the nitrate solution, biosorbent dose, temperature, and the presence of competitive ions on adsorption capacities were investigated. Actual adsorption capacities of ChBT, ChTi, and ChAl at a crosslinker to chitosan solution ratio of 1:40 were 35.68 and 43.62, and 45.38 mg/g as nitrate respectively. The actual adsorption capacities decreased with increase in crosslinker dose. Adsorption equilibrium isotherm models data were well fitted to the linear Freundlich isotherm model. Thermodynamic parameters indicate that adsorption process was spontaneous and endothermic. The adsorption process was better described by a pseudo-second-order equation. The results show that chitosan based organic-inorganic biocomposites were effective, low cost, and reusable for the removal of nitrate from water.