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In this paper, sewage sludge, a solid waste from wastewater treatment plant, which eagerly requires proper treatment was reused as solid support in the form of sewage sludge biochar, then modified with carboxymethyl chitosan to form a bio-adsorbent. Further, carboxymethyl chitosan coating on sewage sludge biochar improved carboxymethyl chitosan’s stability in water. The prepared bio-adsorbent revealed a shorter equilibrium time (<60 min) for Pb(II) adsorption and a superior capacity of 594.17 mg g −1 for Hg(II) adsorption, which are so far the best recorded performance achieved for chitosan based adsorbents. Additionally, the adsorbent was highly selective for heavy metal ions and it also presented a good stability and reusability for industrial applications. These outcomes demonstrate waste valorization through a green, facile and one-pot approach that turns the solid waste of sewage sludge into biochar adsorbent with propitious applications in the elimination of heavy metal ions from wastewater. [ABSTRACT FROM AUTHOR]

Highly efficient magnetic sewage sludge biochar (MSSBC) discloses feasible fabrication process with lower production cost, superior adsorption capacity, usage of waste sewage sludge as resource, selected by external magnetic field and exceptional regeneration property. 2 g L −1 MSSBC exhibited a high adsorption capacity of 249.00 mg g −1 in 200 ppm Pb(II) and the lead-MSSBC equilibrium was achieved within one hour, owing to the existence of the copious active sites. The adsorption kinetics was well described by the pseudo-second-order model while the adsorption isotherm could be fitted by Langmuir model. Mechanism study demonstrated the adsorption involved electrostatic attraction, ion exchange, inner-sphere complexation and formation of co-precipitates at the surface of MSSBC. Additionally, adsorption performance maintained remarkable in a broad pH window. These outcomes demonstrated the promising waste resource utilization by a feasible approach that turns the solid waste of sewage sludge into biochar adsorbent with auspicious applications in elimination of Pb(II) from wastewater. [ABSTRACT FROM AUTHOR]