Titanium Pyrophosphate for Removal of Trivalent Heavy Metals and Actinides Simulated by Retention of Europium.

Huemantzin Balan Ortiz-Oliveros,Rosa María Flores-Espinosa,Suilma Marisela Fernández-Valverde,Eduardo Ordoñez-Regil

doi:10.1155/2017/2675897

Abstract

This work addresses the synthesis of titanium pyrophosphate, as well as the characterization and evaluation of the sorption process of europium, for removal of trivalent heavy metals and actinides simulate. The evaluation of the surface properties of titanium pyrophosphate was carried out determining the surface roughness and surface acidity constants. The values obtained from the determination of the surface roughness of the synthesized solid indicate that the surface of the material presents itself as slightly smooth. The FITEQL program was used to fit the experimental titration curves to obtain the surface acidity constants: log⁡K+ = 3.59 ± 0.06 and log⁡K− = −3.90 ± 0.05. The results of sorption kinetics evidenced that the pseudo-order model explains the retention process of europium, in which the initial sorption velocity was 8.3 × 10−4 mg g−1 min−1 and kinetic constant was 1.8 × 10−3 g mg min−1. The maximum sorption capacity was 0.6 mg g−1. The results obtained from sorption edge showed the existence of two bidentate complexes on the surface.

Highlights

The rapid growth of our population during the last decades has led to an ecological imbalance in our environment with severe consequences and major risks both for our health and our environment
The surface complex constants for the europium species sorbed onto the titanium pyrophosphate were obtained from the sorption isotherms as function of pH using the FITEQL program and the Capacitance Model (CCM)
These results indicate that the sorption of europium occurs in two phases, during the first of which (t ≤ 10 h) the retention velocity is fast and grows exponentially with time, reaching its maximum velocity at times close to 10 h, during which time approximately 50% of the initial europium quantity have been retained

Summary

Introduction

The rapid growth of our population during the last decades has led to an ecological imbalance in our environment with severe consequences and major risks both for our health and our environment. The processes most used are chemical precipitation, coagulation/flocculation, flotation (with dispersed air or dissolved air), electrochemical process, photocatalytic process, inverse osmosis, ion exchange, and sorption [14,15,16,17,18,19,20] Many of these processes are usually efficient but can be limited by the concentration and the physicochemical form of the heavy metal as well as the costs and the difficulties of the operation such as the generation of residual sludge. As far as phosphates are concerned since the discovery of LiFePO4, new materials have been synthesized and identified based on phosphates-based polyanions such as (PO4)3−, (P2O7)4−, or (P3O10)5− [32], which find their application in different fields of knowledge due to their major structural anomalies, such as their anisotropic deformation, low redox potential, and low cost of synthesis [32, 33] These characteristics have motivated the study of the retention of metals in phosphates. Additional, modeling the sorption of the europium onto the titanium pyrophosphate as a function of the pH using a surface complexation model was performed

Experimental

Results and Discussions

Determination of Surface Properties

Conclusions