Improvement in performance of sludge-based adsorbents by controlling key parameters by activation/modification: A critical review

The conversion of sludge into an adsorbent is emerging out as a sustainable alternative for management of the sludge that otherwise considered as a waste. The poor performance of the sludge-based adsorbents limits their practical applications. Different methods and techniques have been reported in literature to improve the performance of sludge-based adsorbents. The data are so diversified that it is become difficult to choose the potential modification/activation techniques to get desired adsorbent performance. In this review we made efforts to correlate the modification/activation technique parameters with performance-controlling parameters (surface area, porosity, surface functionalities, ash content, carbon content). A detailed description of effect preparation and activation techniques on adsorbent properties have been provided. Various physical and chemical activation techniques are discussed in detail. Furthermore, the variation in processing and modification/activation conditions contributes to the differences in the cost involved in the adsorbent preparation. Efforts have been made to materialize the gross cost estimate of the adsorbent to increase their practical applications.