Abstract
This study evaluated the adsorption of Cr6+ from aqueous solution using dead biomass of aquatic plants Salvinia molesta (Kariba weed) and Typha latifolia (broadleaf cattail). The batch experiments were carried out to study the effects of pH, adsorbent dose, initial metal concentration, contact time, agitation speed in rotation per minute (rpm), and temperature. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the adsorbent and analyze the functional groups and morphology of the adsorbent, respectively. The hydroxyl and amine groups were the main functional groups involved in the adsorption. Both adsorbents showed good results at pH 1, metal concentration of 20 mg/L for Cr6+ removal, and adsorption equilibrium was attained within 60 min with 150 rpm at 25 °C. The adsorption rate obtained was above 95% for both the adsorbents at a dose of 0.150 g for S. molesta and 0.8 g for T. latifolia. Isotherm and kinetic models were applied on the adsorption data. The monolayer adsorption capacity (qm) was found to be 33.33 mg/g for S. molesta and 10.30 mg/g for T. latifolia. The Langmuir isotherm was better fitted to S. molesta, while the Freundlich isotherm was better fitted to T. latifolia. It was reported that the pseudo-second-order model (R2 = 0.999) was better fitted to the adsorption data for both the adsorbents. The thermodynamic study was also conducted and found the adsorption process was exothermic and spontaneous. Results revealed the good adsorption potential of S. molesta and T. latifolia, and they can be used for the removal of hexavalent chromium.
Highlights
Chromium pollution is a serious problem of water resources that affects the health of the environment and human beings
It was observed that peak form in Fourier transform infrared spectroscopy (FTIR) spectra did not change so much after C r6+ adsorption and indicated that metal Cr does not cause any significant change in the basic chemical composition of adsorbents
Aquatic plants S. molesta and T. latifolia were used as adsorbents to study their potential to adsorb Cr6+
Summary
Chromium pollution is a serious problem of water resources that affects the health of the environment and human beings. The main sources of chromium discharge are anthropogenic sources like electroplating, pigment manufacturing, cement and steel industries, photography, leather tanning, and magnetic tapes, etc. Cr6+ is considered carcinogenic, mutagenic, toxic, and Department of Environmental Sciences, Maharshi Dayanand University, Rohtak, Haryana 124001, India teratogenic (Wittbrodt and Palmer 1995). It is of main concern because it is very hazardous to human health. Due to the ill effects of C r6+ on human beings, it must be removed from effluents before discharging into water bodies which are the ultimate source of waste disposal
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