Optimization of hardness removal using response surface methodology from wastewater containing high boron by Bigadic clinoptilolite

Abstract

In this study, hardness removal from wastewater containing a high concentration of boron by raw and modified clinoptilolite minerals was investigated. The raw clinoptilolite mineral was modified with HCl and NaOH. Optimum conditions for total and calcium hardness removal from the wastewater were determined by central composite design (CCD) of response surface methodology (RSM). The clinoptilolite dosage, contact time, temperature and dilution ratio were selected as independent variables. Equations that give removal efficiency (%) and removal capacity (mg/g) of total and calcium hardness were obtained through RSM analysis and interactions of independent variables with each other were illustrated by contour graphs. All determination coefficients (R2) were above 0.90. The highest values of removal efficiency (%) and capacity (mg/g) were obtained by NaOH-modified clinoptilolite and its maximum values were above 99% and 12.30 mg/g, respectively.