Valorization of natural diatomite mineral: Application to removal of anionic dye from aqueous solution in a batch and fixed-bed reactor天然硅藻土矿物的高值化利用： 在批式和固定床反应器中去除水溶液中的阴离子染料

In this work, the efficiency of an adsorption process, in which Moroccan diatomite (ND) is used as a low-cost adsorbent to remove Congo red (CR) dye from contaminated waters in batch and column system, was examined. The influence of experimental conditions (pH, adsorbent dose and temperature) on the adsorption of CR onto the ND adsorbent was studied. A study of the adsorption kinetics for CR revealed that a pseudo-second-order model provided the best fit to the experimental kinetic data, and the equilibrium data were well described by the Langmuir isotherm model with an adsorption capacity of 6.07 mg/g using 15 g/L of ND, pH=6, contact time 3 h and 25 °C. On the other hand, the ND regeneration tests were investigated and showed that the desorption reaches at least 50% when using ethanol as eluent. In addition, the adsorption process in a continuous mode was studied. Breakthrough curves were properly represented by the Yoon — Nelson model. Hence, the adsorption capacity of 5.71 mg/g was reached using 0.114 g of adsorbent, CR concentration of 6 mg/L and a flow of 1 mL/min under 25 °C.