Alamoudi Water Research Chair, King Saud University, Riyadh, 11451, Kingdom of Saudi Arabia.
Department of Environmental Sciences, COMSATS Institute of Information Technology, Abbottabad, 22060, Pakistan.
Environ Monit Assess. 2019 Nov 9;191(12):735. doi: 10.1007/s10661-019-7915-0.
Biochar pyrolyzed at 800 °C from banana (B) and orange peels (OP) was applied for sorption of methylene blue (MB) dye in a batch system. OP showed better affinity for MB dye than B with rapid increase in sorption capacity and percent removal for both biochars attaining equilibrium at 30 min. Chemisorption was suggested as the rate limiting step based on the best fitting of the pseudo-second-order reaction kinetics to the batch adsorption data. Linear increase in sorption capacity was seen as the initial MB dye concentration increased from 50 to 300 mg g with a 40 % decrease in removal efficiency. An increase of 90 mg g in sorption capacity for both biochars with a 15 and 30 % increase in removal efficiency for OP and B, respectively, was observed after increasing the solution pH from 2 to 6 or 8. An increase in sorption capacity of about 150 mg g was seen by increasing the biochar dose from 0.1 to 0.5 g. Langmuir isotherm model represented the adsorption data well as reflected by the high values of R (0.99) when using both biochar, while least representation of adsorption data was seen in H-J isotherm as estimated from very low R (0.6-0.66) for both types of biochar. An endothermic nature of MB dye sorption was suggested based on the linear increase in sorption capacity with an increase in solution temperature from 30 to 60 °C. This was further confirmed by the observed positive changes in standard entropy and standard enthalpy while negative values of Gibbs-free energies proposed the non-spontaneous natures of MB dye sorption on to both biochars. The effective sorption of MB dye demonstrated the potential of plant-based biochar as economically viable adsorbents for MB dye.
800°C 热解香蕉皮（B）和橙皮（OP）制备的生物炭用于吸附亚甲基蓝（MB）染料的批处理系统。OP 对 MB 染料的亲和力优于 B，吸附容量和去除率在 30 min 内迅速增加达到平衡。基于伪二级反应动力学对批量吸附数据的最佳拟合，推测化学吸附是限速步骤。随着初始 MB 染料浓度从 50 增加到 300 mg g，吸附容量线性增加，去除效率降低 40%。当溶液 pH 值从 2 增加到 6 或 8 时，OP 和 B 的吸附容量分别增加了 90 mg g 和 40%，去除效率分别增加了 15%和 30%。当生物炭剂量从 0.1 增加到 0.5 g 时，吸附容量增加了约 150 mg g。Langmuir 等温线模型很好地代表了吸附数据，反映了两种生物炭的高 R 值（0.99），而 H-J 等温线对吸附数据的表示最差，估计两种类型的生物炭的 R 值都非常低（0.6-0.66）。根据吸附容量随溶液温度从 30°C 增加到 60°C 的线性增加，表明 MB 染料吸附是吸热的。这进一步通过观察到标准熵和标准焓的正向变化得到证实，而吉布斯自由能的负值表明 MB 染料在两种生物炭上的吸附是非自发的。MB 染料的有效吸附证明了基于植物的生物炭作为经济上可行的 MB 染料吸附剂的潜力。
