This study investigates the influence of Ca²⁺ and Mg²⁺ on the removal of F⁻ by magnesium potassium phosphate (MPP) from water. The kinetic experiments reveal that the F⁻ concentration decreased from 3.5 to 3.31 mg L⁻¹ in a single (F⁻) system and to 1.45 mg L⁻¹ in a ternary system (F⁻, Ca²⁺, and Mg²⁺) after 1 min, respectively. Thus, the F⁻ removal efficiencies are found to increase by about 53% with the co‐active effect of Ca²⁺ and Mg²⁺ in the solution. Moreover, Ca²⁺ and Mg²⁺ are almost completely removed in the F⁻, Ca²⁺, and Mg²⁺ system. According to the pseudo‐first‐order modeling, the rate constants k for F⁻, Ca²⁺, and Mg²⁺ are 0.00348, 0.0106, and 0.0159 min⁻¹ respectively; thus, Mg²⁺ > Ca²⁺ > F⁻. In the ternary system, the removal efficiencies are 53.29–66.03% for F⁻, 99.99–100% for Ca²⁺, and 87.21–95.19% for Mg²⁺ with initial pH 5–10. The removal efficiencies of F⁻ increases with increases in initial concentrations of F⁻, Ca²⁺, and Mg²⁺. The removal of F⁻ is governed by two routes: 1) adsorption by electrostatic interactions and outer sphere surface complexation; 2) co‐precipitation with Ca₃(PO₄)₂, CaHPO₄, Mg₃(PO₄)₂, and Mg(OH)₂.

中文翻译：

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Ca2 +和Mg2 +对磷酸镁钾去除F-的影响

本研究探讨Ca的影响²⁺和Mg ²⁺对去除的F ^-从水磷酸镁钾（MPP）。动力学实验表明，在F ^-浓度为3.5降低到3.31毫克的L ^-1在一个单一的（F ^- ）系统和1.45毫克的L ^-1的三元体系（F ^- ，钙²⁺和Mg ²⁺） 1分钟后。因此，在F ^-去除效率发现约53％与Ca的共活性效果增加²⁺和Mg ²⁺在溶液中。此外，Ca ²⁺和Mg²⁺被的F几乎完全除去^- ，钙²⁺和Mg ²⁺系统。根据伪一阶模型的速率常数ķ与F ^- ，钙²⁺和Mg ²⁺是0.00348，0.0106和0.0159分钟^-1分别; 因而，镁²⁺ >的Ca ²⁺ >˚F ^- 。在三元体系中，去除率是53.29-66.03％与F ^-，99.99-100％为的Ca ²⁺，和87.21-95.19％镁²⁺与初始pH 5-10。F的去除效率^-与F中的初始浓度的增大而增大^- ，钙²⁺和Mg ²⁺。F的去除^-通过两个途径支配：1）通过静电相互作用和外球表面络合吸附; 2）与Ca ₃（PO ₄）₂，CaHPO ₄，Mg ₃（PO ₄）₂和Mg（OH）₂共沉淀。