Sequential adsorptive removal of phosphate, nitrate and chromate from polluted water using active carbon derived from stems of Carissa carandas plant Wondwosen Kebede Biftu a,b , M. Suneetha c and Kunta Ravindhranath a,* a Department of Chemistry, Koneru Lakshmaiah Education Foundation, Green Fields, Vaddeswaram-522 502, Guntur Dt., Andhra Pradesh, India b Ethiopian Radiation Protection Authority, Addis Ababa, Ethiopia c Department of Chemistry, RGUKT, Srikakulam, Andhra Pradesh, India *Corresponding author. E-mail: ravindhranath.kunta@gmail.com Abstract Sulphuric acid-generated active carbon from stems of Carissa carandas plant is investigated successfully as an adsorbent for the sequential removal of phosphate, nitrate and chromate from polluted water. Controlling par- ameters are investigated and optimized for the maximum removal of the pollutants. At pH: 7, phosphate and nitrate can be simultaneously removed, while at pH: 2, chromate can be sequentially removed from the admix- tures of the three pollutants. The active carbon is characterized using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). Sorption mechanisms are investigated using various adsorption isotherms and kinetic models. Thermodynamics parameters are evaluated. The data reveal the Langmuir isotherm model of adsorption, pseudo-second-order kin- etics and spontaneity of sorption processes. Langmuir individual maximum adsorption capacity is: 72.75 mg/g for chromate; 63.40 mg/g for phosphate; and 49.15 mg/g for nitrate. The active carbon can be regenerated and reused. The method is used for the removal of all three pollutant ions from polluted water. The merit of this inves- tigation is that an active carbon is identified with good adsorption capacities for the successful sequential removal of phosphate, nitrate and chromate ions from polluted water. Key words: activated carbon, Carissa carandas plant, chromate, nitrate, phosphate, water remediation Highlights • An active carbon is synthesized from stems of Carissa carandas plant. • Sequential separation of Cr(VI), PO 3 4 and NO  3 from polluted water is effected. • Simultaneous quantitative separation of nitrate and phosphate is possible at pH: 7. • Data reveal Langmuir model, pseudo-second-order and spontaneity of sorption process. • Adsorption capacities are high in comparison with reported values in literature. Graphical Abstract © IWA Publishing 2021 Water Practice & Technology Vol 16 No 1 117 doi: 10.2166/wpt.2020.102 Downloaded from http://iwaponline.com/wpt/article-pdf/16/1/117/836153/wpt0160117.pdf by guest on 24 December 2023