Paper waste sludge derived-hydrochar modified by iron (III) chloride for effective removal of Cr(VI) from aqueous solution: Kinetic and isotherm studies. (February 2021)

• Record Type: Journal Article
• Authors: Nguyen, Lan Huong; Van, Huu Tap; Nguyen, Quang Trung; Nguyen, Thu Huong; Nguyen, Thi Bich Lien; Nguyen, Van Quang; Bui, Thu Uyen; Le Sy, Hung
• Is Part Of: Journal of water process engineering. Volume 39(2021)
• Publication Date: 2021-02
• Subjects: Adsorption -- Cr(VI) -- Hydrochar -- Iron -- Paper waste sludge; Water-supply engineering -- Periodicals; Saline water conversion -- Periodicals; Seawater -- Distillation -- Periodicals; Sanitary engineering -- Periodicals; Sewage -- Purification -- Periodicals; 627
• DOI: 10.1016/j.jwpe.2020.101877
• Languages: English
• ISSNs: 2214-7144

Abstract

Highlights: Pristine hydrochar (PSH) was generated from paper waste sludge with support of NaOH. The PSH was modified by iron at the most suitable ratio of 15 % (PSH-Fe15). The adsorption capacity of PSH-Fe15 was higher than that of PSH by 1.5 times. The Cr(VI) adsorption main mechanism on hydrochar was adsorption-coupled reduction. The PSH-Fe15 was the low-cost adsorbent with reusability through five cycles. Abstract: This work investigated Cr(VI) adsorption onto pristine and iron modified hydrochar (PSH and PSH-Fe15, respectively) which were generated from paper waste sludge. The results indicate that the hydrothermal carbonization temperature of 200 °C was the most suitable for hydrochar production. The batch experiments and the adsorption isotherm and kinetic of Cr(VI) onto PSH and PSH-Fe15 were conducted and used to elucidate the adsorption mechanisms. The results demonstrate that the Cr(VI) adsorption capacity and efficiency onto both PSH and PSH-Fe15 reached equilibrium after 120 min at pH 3 and an initial Cr(VI) concentration of 60 mg/L. In this condition, the adsorption capacities were 5.94 mg/g and 8.67 mg/g and the removal efficiencies were 39.62 % and 57.80 % for PSH and PSH-Fe15, respectively. The adsorption processes were well described by the Sips and Redlich–Peterson isotherm models (with R 2 of 0.9895, 0.9987 and 0.9947 and 0.9981 for PSH and PSH-Fe15, respectively) and pseudo-second-order kinetic model (with R 2 of 0.98412 and 0.99681, respectively, for PSH and PSH-Fe15). The analysis of characteristics of PSH and PSH-Fe15 indicates the rough and heterogamous surface structures. Moreover, there was presence of iron ions on PSH-Fe15 based on EDS analysis and appearance of oxygen-containing surface functional groups recorded through FTIR results. Finally, it was observed that the reduction of Cr(VI) to Cr(III) caused by iron ions on PSM-Fe15's surface and the presence of OH groups resulting in the precipitation of Cr(OH)3 on the hydrochar's surface was the main mechanism of Cr(VI) adsorption onto PSH-Fe15.