Studies on Taguchi’s optimization for biosorbent developed from waste eggshell material for water defluoridation

Abstract

Excess fluoride intake from drinking water is a serious concern for human health posing mainly dental/skeletal fluorosis and other multiorgan manifestation. Recent research is being focus on developing a new biosorbent from calcium-rich waste materials with thermal treatment for removal from water since it has high affinity and greater potential for deflouridation. The present research developed a new biosorbent from waste eggshell for deflourdation from water. Taguchi’s orthogonal array was used for process variables optimization to acquire the maximum removal. The fluoride uptake capacity of 10.69 and fluoride removal percentage of 86.67% were acquired for the eggshell sorbent at optimum values of process variables of pH: 7 0.1, adsorbate concentration: 15 agitation time: 60 min, eggshell dose: 14 and temperature: 303 K. ANOVA analysis indicates the contribution of process variables in descending order as adsorbate concentration 39.76% > pH 39.33% > temperature 12.34% > biosorbent dose 6.42% > agitation time 2.14%. Freundlich isotherm and second-order kinetic model were best fitted for the sorption of fluoride. Thermodynamic parameters (ΔH = 42.33 and ΔS = 0.240 ) indicate endothermic and spontaneous fluoride sorption. The sorption elution studies with 0.1 N NaOH suggest the eggshell sorbent could be reused up to three cycles. The influence of co-ions was obtained as < < < The eggshell sorbent was also shown feasibility for defluoridation from real water samples.