Abstract
Developing efficient adsorbent materials for water treatment is deemed as one of the key solutions towards mitigating the contaminated water problem. Herein, several Hierarchical Porous Carbons (HPCs) with large mesopore volumes (up to 3 cm3/g) and a wide range of BET surface areas (747–1037 m2/g) were synthesized, and their heavy metal removal behaviors were investigated. Specifically, simulated lead and cadmium aqueous solutions were used to investigate the HPCs adsorption performance towards lead and cadmium removal. All the HPCs demonstrated high affinities towards lead removal compared with cadmium. Additionally, a systematic investigation was carried out to understand the structure—performance relationships for the HPCs. Interestingly, varying the adsorbent pore structure leads to different adsorbent behavior for lead compared with cadmium. The textural characteristics of the HPCs have a limited effect on the removal of cadmium ions. Accordingly, to expedite cadmium removal from aqueous samples, factors other than textural characteristics (i.e., surface chemistry) might enhance the removal process. Conversely, the removal of lead ions can be significantly controlled by the HPCs pore structure. HPC1221 (with 17 nm mesopore size, 2.8 cm3/g pore volume, 907 m2/g) showed the maximum adsorption capacity value of 12.32 mg/g for Cd2+ and 89 mg/g for Pb2+ compared to other HPCs. The significant adsorption parameters were evaluated using the response surface methodology (RSM) design. We believe that the reported insights for the structure–performance relationships will be useful for better designing highly efficient adsorbent materials.
Highlights
The shortage and decline in clean water is a critical issue and a threat to many communities in the developing world
A series of hierarchical porous carbons with abundant mesopores and macropores were fabricated via the ice-templation approach
Cadmium and lead responses vary in their dependence on the textural characteristics of Hierarchical Porous Carbons (HPCs)
Summary
The shortage and decline in clean water is a critical issue and a threat to many communities in the developing world. Activated carbon (AC) has been widely utilized for water treatment purposes, especially for heavy metal removal due to its characteristic high surface properties. Compared with other adsorbent materials, activated carbons often possess high surface area and porous structure that can enhance the heavy metal uptake. Brunauer, Emmett and Teller (BET) surface area does not always demonstrate a positive correlation with the specific capacity of the carbon materials This has been associated with the fact that high values of BET surface area might have resulted from large fractions of non-accessible micropores. Hierarchical porous carbon HPCs with controllable pore (size and volume), high surface area, and high mesopore fraction will be synthesized via the icetemplation approach using the same precursor and used for aqueous heavy metals adsorption. Such a tunable HPC synthesis approach allows for a close and accurate investigation of the impact of textural characteristics on HPC removal behavior of HPCs toward heavy metals
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