Abstract
Recently, hydrothermal carbonization emerges as the most viable option for the management of solid waste with high moisture content. Sludge derived hydrochar is used as an adsorbent for emerging contaminants or micro-pollutants in the domain of sustainability. Current study demonstrates the KOH activation of hydrochar produced from paper board mill sludge and evaluates its removal potential of a Non-steroidal anti-inflammatory drug, Diclofenac from aqueous solution. The activated hydrochars exhibited porous, spherical micro-structures with higher fraction of oxygenated functional groups paving way for the efficient adsorption of Diclofenac. The effect of initial Diclofenac concentration and contact time was ascertained using adsorption kinetics and isotherms. The adsorption kinetics exhibited second-order reaction for all adsorbents indicating higher coefficient of determination (R2 > 0.9). The Diclofenac adsorption on hydrochars followed Langmuir isotherm model with the post-activated hydrochar recording a highest adsorption capacity of 37.23 mg g−1 in 40 mg L−1 initial Diclofenac concentration at 15 h equilibrium time.
Highlights
Generation of C O2 during simultaneous gasification
The non-steroidal anti-inflammatory drug (NSAID) are consumed by around 30 million people per day in average and these are excreted into the sewer system as parent chemicals or intermediates due to inadequate metabolization[17]
The zeta potential of the HC was − 17.1 mV while, it further reduced to − 20.6 mV and − 38 mV for pre-activated hydrochar (PRHC) and postactivated hydrochar (POHC), respectively
Summary
Generation of C O2 during simultaneous gasification. During KOH activation, functional groups like phenolic, lactone, carbonyl, hydroxyl and carboxyl are generated. Activated carbon with high adsorption sites and porous nature help in removing emerging contaminants like Diclofenac from polluted environments. The NSAIDs are consumed by around 30 million people per day in average and these are excreted into the sewer system as parent chemicals or intermediates due to inadequate metabolization[17] These chemicals have a potential threat to the environment even at low concentration of ng L −1 or μg L−1. Most of the studies involved in the removal of Diclofenac through adsorption utilizes biodegradable non-hazardous raw material, but the present investigation attempts to utilize paper board mill sludge as a substrate for adsorbent preparation. The management of sludge is a major problem for the industries due to its hazardous nature and the cost of its disposal With this background, the manuscript illustrates the KOH activation of hydrochar produced from paper board mill ETP sludge. The raw hydrochar and activated hydrochars were used for the removal of Diclofenac from synthetic aqueous solution using batch adsorption studies (Fig. 1)
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