Comparative study of sun-dried and oven-dried Malva sylvestris biomass for high-rate Cu(II) removal from wastewater

Abstract

Abstract This study compared the sun- and oven-dried powdered Malva sylvestris for removing Cu(II) from aqueous solution. The fresh and Cu-loaded adsorbents characteristics were analyzed by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller testing and scanning electron microscopy. The studied parameters that affect adsorption capacity were pH (2–7), initial copper concentration (50–150 mg/L), contact time (3–60 min), adsorbent dosage (1–20 g/L) and temperature (10–35 °C). The results showed that the maximum removal of Cu(II) was observed at pH 5 for both adsorbents. The amount of Cu(II) adsorbed onto both adsorbents increased as the contact time and the initial concentration of Cu(II) increased. The adsorbents exhibited the highest Cu(II) removal at a temperature of 35 °C. The adsorption data obtained at different temperatures was described well by the Langmuir isotherm (qm = 172.61–202.81 mg/g for oven-dried and 118.49–133.45 mg/g for sun-dried) and the pseudo second-order kinetic model (R2 = 0.999 and 0.993–0.997 for oven- and sun-dried, respectively). An electroplating wastewater sample was effectively treated using oven-dried powdered M. sylvestris. The adsorption efficiency of the oven- and sun-dried M. sylvestris after five reuses was 70.4% and 26.1%, respectively. Generally, the oven-dried adsorbent was shown to be more effective than the sun-dried for removal of Cu(II) from wastewater. The cost assessment indicated that the oven-dried M. sylvestris is a more economical adsorbent than sun-dried one.