The combination of red mud (RM) and phosphogypsum (PG) is an interesting alternative for reusing these by-products as either adsorbent or soil amendment. In this context, this study aimed to evaluate cation (cadmium and lead) and anion (arsenate and phosphate) adsorption and desorption on RM, PG, and their blendings at different proportions (w/w): 100% PG, 75% PG + 25% RM, 50% PG + 50% RM, 25% PG + 75% RM, and 100% RM. Cadmium, lead, arsenate, and phosphate adsorption and desorption tests were carried out using 0.01 mol L⁻¹ Ca(NO₃)₂ for cations and 0.03 mol L⁻¹ NaCl for anions. The initial concentrations of cations and anions were 0.33 and 0.66 mmol L⁻¹, respectively, and the equilibrium pH was 5.5 ± 0.2 (adsorbent:solution ratio of 1:100). RM adsorbed 99% of phosphate, 92% of lead, 87% of arsenate, and 26% of cadmium. The blending containing 75% of RM and 25% of PG adsorbed 95% of phosphate, 97% of lead, 76% of arsenate, and 32% of cadmium. The amount of cadmium and arsenate adsorbed increased with increasing RM proportion. Cadmium (16%) and arsenate (6.9%) desorption percentages were higher than lead (0.4%) and phosphate (1.3%). Effectively adsorbed percentages followed the decreasing order: phosphate (98%) > lead (91%) > arsenate (83%) > cadmium (19%) for RM and lead (97%) > phosphate (94%) > arsenate (70%) > cadmium (26%) for the mixture containing 75% of RM and 25% of PG.

Graphic Abstract

中文翻译：

---

镉，铅，砷和磷酸盐在红泥与磷石膏结合上的吸附

赤泥（RM）和磷石膏（PG）的组合是将这些副产品作为吸附剂或土壤改良剂再利用的有趣替代方法。在这种情况下，本研究旨在评估阳离子（镉和铅）和阴离子（砷酸盐和磷酸盐）在RM，PG及其混合物中以不同比例（w / w）的吸附和脱附：100％PG，75％PG + 25％RM，50％PG + 50％RM，25％PG + 75％RM和100％RM。使用0.01 mol L ^-1 Ca（NO ₃）₂作为阳离子和0.03 mol L ^-1 NaCl作为阴离​​子进行镉，铅，砷酸盐和磷酸盐的吸附和解吸测试。阳离子和阴离子的初始浓度为0.33和0.66 mmol L ^-1，平衡pH值为5.5±0.2（吸附剂：溶液的比例为1：100）。RM吸附了99％的磷酸盐，92％的铅，87％的砷酸盐和26％的镉。包含75％的RM和25％的PG的共混物吸附了95％的磷酸盐，97％的铅，76％的砷酸盐和32％的镉。随着RM比例的增加，镉和砷的吸附量增加。镉（16％）和砷酸盐（6.9％）的解吸百分比高于铅（0.4％）和磷酸盐（1.3％）。有效吸附百分比按照降序排列：磷酸盐（98％）>铅（91％）>砷酸盐（83％）>镉（RM）中的镉（19％）>铅（97％）>磷酸盐（94％）>砷酸盐（70％） ）>镉（26％），用于含有75％的RM和25％的PG的混合物。

图形摘要