Comparative adsorption of remazol brilliant blue R and copper in aqueous solutions by carbon nanotubes with different levels of carboxyl group and specific surface area

Abstract

In order to investigate the effects of carboxyl group and specific surface area of carbon nanotubes (CNTs) on dye and heavy metal removal in wastewater, four kinds of CNTs with different carboxyl group content and specific surface area were used to remove remazol brilliant blue R (RBBR) and Cu2+ from aqueous solution in batch experiment. The results showed that the CNTs with large specific surface area displayed high RBBR removal efficiency (RE) and modification with carboxylation revealed a positive effect on copper ion removal. When pH = 1, CNTs without carboxylation and with an outer diameter of less than 8 nm (C8) had the highest RBBR RE (99.1%), while pH = 9, CNTs with an outer diameter of less than 8 nm and containing 3.86% of carboxyl groups (CC8) had the highest Cu2+ RE (89.68%). According to the Langmuir equation, the maximum adsorption capacity of C8 on RBBR and CC8 on Cu2+ were 291.55 mg g−1 and 49.26 mg g−1, respectively. The RBBR RE of CNTs depended on their surface area and the copper RE was mainly dominated by the level of carboxyl group. This work provides a very efficient approach for exploring promising CNTs for wastewater treatment.