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The treatment of beryllium wastewater has become a major problem in industry. In this paper, CaCO 3 is creatively proposed to treat beryllium-containing wastewater. Calcite was modified by an omnidirectional planetary ball mill by a mechanical-chemical method. The results show that the maximum adsorption capacity of CaCO 3 for beryllium is up to 45 mg/g. The optimum treatment conditions were pH = 7 and the amount of adsorbent was 1 g/L, and the best removal rate was 99%. The concentration of beryllium in the CaCO 3 -treated solution is less than 5 μg/L, which meets the international emission standard. The results show that the surface co-precipitation reaction between CaCO 3 and Be (II) mainly occurs. Two different precipitates are generated on the used-CaCO 3 surface; one is the tightly connected Be (OH) 2 precipitation, and the other is the loose Be 2 (OH) 2 CO 3 precipitation. When the pH of the solution exceeds 5.5, Be 2+ in the solution is first precipitated by Be (OH) 2 . After CaCO 3 is added, CO 3 2- will further react with Be 3 (OH) 3 3+ to form Be 2 (OH) 2 CO 3 precipitation. CaCO 3 can be considered as an adsorbent with great potential to remove beryllium from industrial wastewater., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Lotus leaf was used as raw material to prepare HNO 3 -activated carbon with 1.5:1 (HNO 3 :lotus leaf) (wt:wt) impregnation. Then, the activated carbon was modified by Fe(NO 3 ) 3 to obtain Fe-activated carbon (Fe-AC). The adsorption test results show that Fe-AC maximum saturated adsorption capacity (Q m ) is 45.68 mg/g when the Fe(NO 3 ) 3 loading is 5% of the total activated carbon, pH = 6, and the temperature is 35 ℃. The adsorption effect of Fe-AC under neutral conditions is better than that under alkaline and acidic conditions. The modified activated carbon has better adsorption selectivity. The obtained material (Fe-AC) was characterized by N 2 adsorption-desorption isotherm, SEM, FT-IR, BET, XRD, XPS, and pH pzc . The total pore volume, specific surface area, and zero charges of modified activated carbon were increased. The types of modified functional groups were reduced, and the iron reacted with the functional groups, providing ion exchange sites for the adsorption of beryllium. The adsorption thermodynamics showed that the adsorption process was spontaneous and endothermic. The adsorption mechanism of Fe-AC to beryllium is mainly chemical adsorption., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)