Study on adsorption properties and mechanism of sodium hydroxide–modified ball-milled biochar to dislodge lead(II) and MB from water

Heavy metal pollution and organic wastewater treatment have attracted extensive attention of researchers. Adsorption method is widely used in wastewater treatment because of its low price and high efficiency. As a natural, cheap biomass material, bamboo powder is of great significance to develop it into an economical and efficient biochar for wastewater treatment. A new type of ball-milled biochar (BMBC) adsorbent was prepared by pyrolysis of bamboo powder under an inert atmosphere, activated with sodium hydroxide solution and ball milling. The specific surface area of BMBC increased from 29.21 to 60.49 m 2 /g, and the carboxyl and hydroxyl groups on the pyrolyzed carbon surface also obviously increased after ball milling. The results of bath adsorption experiments showed that BMBC exhibited excellent adsorption capacity towards both Pb(II) (170.52 mg/g) and methylene blue (MB, 419.11 mg/g) at 308 K. Based on a systematic study on the effect of various working conditions (including concentration, temperature, pH value, and ionic strength), it was demonstrated that pseudo-second-order kinetic equation might match the adsorption process ( R 2  > 0.9934) and Langmuir model ( R 2  > 0.9924); adsorptions were thermodynamically endothermic and occurred spontaneously. The ball milled alkalization-modified bamboo biochar can potentially be applied to remove heavy metal and cationic pollutants from wastewater.