Cu (II) removal from aqueous wastewaters by adsorption on the modified Henna with Fe3O4 nanoparticles using response surface methodology

•Henna was modified by Fe3O4 nanoparticles for Cu (II) adsorption.•RSM and CCD were used to optimize the adsorption effective parameters.•The parameters were pH, initial solution concentration, adsorbent dosage and process time.•A useful correlation was investigated for Cu (II) removal.•The modified Henna dramatically adsorbed Cu (II) from an aqueous wastewater. In this research, the capability of modified Henna with Fe3O4 nanoparticles adsorbent was studied in order to remove the ion Cu (II). Response surface method and central composite design were used to minimize number of experiments (21 runs) and optimize the effective parameters. The parameters were pH (2–6), initial solution concentration (10–100mg/l), adsorbent dosage (0.1–1g), and process time (20–150min). It was concluded that Cu (II) removal increased from 0.73% to 99.11% by increasing the pH from 2 to 5.2 (maximum adsorption was at pH 5.2). The removal was decreased up to 66% by the initial solution concentration enhancement (10–100mg/l). Furthermore, the removal was increased from 41.65% to 97.05% by the augmentation of the amount of adsorbent dosage (from 0.1 to 1g). A perfect correlation (with R2=0.9986) between the statistical model and experiment was found for Cu (II) removal from aqueous wastewater using the adsorbent. The Langmuir and Freundlich isotherm models were also applied as adsorption mechanism. A good agreement (with R2=1) between the Langmuir model and experimental data was investigated however Freundlich model confirmed that the modified Henna is a proper adsorbent in Cu (II) adsorption process.