Preparation, characterization, and application of macroporous activated carbon (MAC) suitable for the BAC water treatment process

Abstract

To address the sharp decrease in efficiency of the biological activated carbon (BAC) process at low temperatures, a new type of activated carbon (AC), macroporous activated carbon (MAC), was developed from bamboo waste scraps via a special compression, carbonation and activation process without the introduction of chemicals. MAC contains not only the micron-level macropores (Vmaco > 0.71 ml/g) sufficient for bacteria to access and multiply, but ensures the developed smaller pores (particularly micropores, Vmicro > 0.41 ml/g) and a higher hardness (>90%). In addition, the desired volume of macropores with an adiabatic function, which will provide livable space environment for bacteria, can be obtained by adjusting the compression ratio (1:5–1:10). Because of the maximum macropore volume (Vmaco = 0.805 ml/g) and the most abundant macropore distribution (particularly diameters>10,000 nm), MAC (1:6) was selected for the parallel experiment in the laboratory, taking three representative commercial ACs (PICABIOL® 2, raw coal AC-1 and briquetting AC-2) as controls, in which the filtration effluent of a water treatment plant was used as the influent and glucose was added to accelerate bacterial growth. The results showed that MAC (1:6) exhibited the highest DOC removal and biological activity at room/low temperatures (4 °C), indicating that the abundant macropores distribution with adiabatic function in MAC (1:6) is conducive to the growth and breeding of microorganisms. It is equivalent to artificially increasing the surface suitable for bacteria attachment. This is coupled with the higher adsorption capacity for pollutants supplied by the developed micropores in MAC, which provided the substrate for bacteria growth, thus forming a benign circle for water treatment by the BAC process. The results provide significant technical support for BAC's application, particularly at cold temperatures.