Optimize the Preparation of Novel Pyrite Tailings Based Non-sintered Ceramsite by Plackett-Burman Design Combined With Response Surface Method for Phosphorus Removal.

Ruihuan Chen,Da Ouyang,Zhida Huang,Shuyi Chu,Zhenlin Pan,Xiangting Wu,Rengui Weng,Jibo Xiao,Yunlong Yang

doi:10.3389/fchem.2022.850171

Abstract

The large amount of untreated pyrite tailings has caused serious environmental problems, and the recycling of pyrite tailings is considered as an attractive strategy. Here, we reported a novel non-sintered ceramsite prepared with pyrite tailings (PTNC) as the main active raw material for phosphorus control, and the dosage effect of ingredients on total phosphorus (TP) removal ability was investigated. The results from Plackett-Burman Design (PBD) suggested the dosages of dehydrated sludge, sodium bicarbonate, and cement were the factors which significantly affect the TP removal ability. The Box-Behnken Design (BBD) based response surface methodology was further employed, and it indicated the interactions between different factors, and the optimized recipe for PTNC was 84.5 g (pyrite tailings), 10 g (cement), 1 g (calcined lime), 1 g (anhydrous gypsum), 3 g (dehydrated sludge), and 0.5 g (sodium bicarbonate). The optimized PTNC was characterized and which presented much higher specific area (7.21 m2/g) than the standard limitation (0.5 m2/g), as well as a lower wear rate (2.08%) rather than 6%. Additionally, the leaching metal concentrations of PTNC were far below the limitation of Chinese National Standard. The adsorption behavior of TP on PTNC was subsequently investigated with batch and dynamic experiments. It was found that the calculated max adsorption amount (qmax) was about 7 mg/g, and PTNC was able to offer a stable TP removal ability under different hydraulic retention time (HRT). The adsorption mechanism was discussed by model fitting analysis combined with XRD and SEM characterization, and cobalt phosphide sulfide was observed as the newly formed substance through the adsorption process, which suggested the existing of both physical and chemical adsorption effect. Our research not only offered an economic preparation method of ceramsite, but also broadened the recycling pathway of pyrite tailings.

Highlights

Pyrite is the most abundant and widespread sulfide mineral which is mainly composed of iron and sulfur, and has been used as the raw material for sulfuric acid production for decades (Chandra and Gerson 2010)
As the dosage of cement was over 30 g, the decreasing of removal rate can be ascribed to the lower porosity of PTNC, which was almost 0 as 50 g cement was added
Adding of quicklime can increase the content of Ca in ceramsite to some extent, which is beneficial to the removal of total phosphorus (TP)

Summary

Introduction

Pyrite is the most abundant and widespread sulfide mineral which is mainly composed of iron and sulfur, and has been used as the raw material for sulfuric acid production for decades (Chandra and Gerson 2010). With the large-scale mining of pyrite, the pyrite tailings have caused serious environmental problems. As sulfide-rich waste materials, pyrite tailings can be oxidized in the presence of air and water (Garcia et al, 2005) spontaneously, which causes acid mine drainage (AMD) (Malmström et al, 2006). Remediation strategies are effective but unsustainable; recycling of mine tailings is considered as a more economical way for reducing of tailings amount and limiting acid mine drainage formation. One important property of pyrite tailings should not be ignored, that is, large amounts of active reaction sites due to the existing of Fe and S in pyrite tailings, which can be used for removal of various pollutants (Yang et al, 2017). It is promising to use pyrite tailings as the active material to enhance the wastewater treatment process

Methods

Results

Conclusion