Optimization of lead adsorption of mordenite by response surface methodology: characterization and modification

Background: in order to remove heavy metals, water treatment by adsorption of zeolite is gaining momentumdue to low cost and good performance. in this research, the natural mordenite was used as an adsorbent toremove lead ions in an aqueous solution.methods: the effects of adsorption temperature, time and initial concentration of lead on the adsorption yieldwere investigated. response surface methodology based on box-behnken design was applied for optimization.adsorption data were analyzed by isotherm models. the process was investigated by batch experiments; kinetic andthermodynamic studies were carried out. adsorption yields of natural and hexadecyltrimethylammoniumbromide-modified mordenite were compared.results: the optimum conditions of maximum adsorption (nearly 84 percent) were found as follows: adsorption timeof 85-90 min, adsorption temperature of 50°c, and initial lead concentration of 10 mg/l. at the same optimumconditions, modification of mordenite produced 97 percent adsorption yield. the most appropriate isotherm for theprocess was the freundlich. adsorption rate was found as 4.4. thermodynamic calculations showed that the adsorptionwas a spontaneous and an exothermic process.conclusions: quadratic model and reduced cubic model were developed to correlate the variables with theadsorption yield of mordenite. from the analysis of variance, the most influential factor was identified as initial leadconcentration. at the optimum conditions modification increased the adsorption yield up to nearly 100 percent.mordenite was found an applicable adsorbent for lead ions especially in dilute solutions and may also be applicable inmore concentrated ones with lower yields.