Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : leaching

The Solubility of Phosphogypsum and Recovery of Heavy and Radioactive Elements

Waleed T. Rashid; Israa A. Alkadir; Moayyed G. Jalhom

Engineering and Technology Journal, 2020, Volume 38, Issue 10A, Pages 1470-1480
DOI: 10.30684/etj.v38i10A.907

The essential purpose of this paper is to illustrate and inspect the leaching characteristics of Iraqi Phosphogypsum (PG). The paper presents the results of the dissolution characteristics of heavy and radioactive elements from PG, which is a by-product result from the industry of phosphate fertilizers. Leachability of heavy and radioactive elements in deionized water that has been inspected under various states of leaching, including solid/liquid ratio (10, 20 and 50 /1g/L) and temperatures (25, 45 and 85 °C), with constant other parameters such as string speed (300 rpm) and contact time (60 minutes). For the most analysis elements, the progressive release of the metals, in addition to the major elements reflects high mobility. The mobility of trace metals in PG has been generally classified into three main degrees: (1) high mobility elements such as Pb, Zn, Mn, and Cr; (2) moderate mobility elements such as Sr, V, Ba,Y,Hg, K and Ni; and (3)l ow mobility elements like Ca,Cu,Fe, and Ag. The maximum concentrations of the most of the metals were attained from a leaching state of 10/1g/L. Regarding temperature, the experimental results revealed that the PG solubility to leaching out elements increases noticeably as the applied temperature ranges from 25 to 45 °C; after this degree, the leaching efficiency decreases. Chloride had a positive and negative effect on the solubility of phosphorus. Calcium chloride had an adverse effect on solubility and observed reduced solubility with increased chloride. While the positive effect of sodium and magnesium chloride was observed, the solubility ratio increased with the increase of chlorides. However, the effect of magnesium chloride was higher compared to the sodium chloride one

Cement Based Solidification/Stabilization Leaching Performances of Selected Heavy Metal Ions under Different pH Extractions

Basim A. Hussain A. Hussain; Shahlaa E. Ebrahim; Abbas H. Sulaymon

Engineering and Technology Journal, 2019, Volume 37, Issue 2C, Pages 268-274
DOI: 10.30684/etj.37.2C.11

Liquid to solid partitioning as a function of pH leaching Procedure LSP EPA method 1313 was carried out to test the effectiveness , performance and efficiency of the cement-based solidification / stabilization (S/S) of heavy metals contaminated sand samples using Ordinary Portland Cement OPC type A . Two cement based mix designs ( 7 and 25 % ) have been applied to (S/S) sand contaminated samples with different heavy metal ions ( Pb , Cu , Cr , and Cd ) having the following concentrations ( 500 , 1500 and 3000 mg / kg ). Fixed water to cement ratio of 0.45 was maintained for all the experiments. Effective retention levels for the heavy metal ions was achieved using a 25 % OPC mix ratio to (S/S) the contaminated samples even when the extraction solutions were of pH levels as low as 2. Leaching experiments showed that as the pH level of the extraction solution is reduces and as the OPC content in the (S/S) samples is reduced the more heavy metal ions that can leach out. Up to 80 % of chromium, cadmium, lead, and copper ions leachability can be prevented when higher cement content is introduced to the solidification / stabilization process under the same pH extraction. Acidic extraction effects and solubilized the Calcium – Silica – Hydrate (C-S-H) gel that is created by the OPC binder, which holds, and contain the heavy metal ions and thus results in more release of those ions into the extraction solutions. The alkaline environments provided by the cement binder are believed to have participated in the precipitation of several metal ions such as cadmium and lead io, leading to their less detection in the leaching extracts. Alkaline extraction experiments (pH 8-13) showed that the mobility of the metal ions under the same experimental conditions followed the order of pb> Cr > Cu > Cd in samples of various cement contents.