Phosphorus removal from secondary wastewater effluent using copper smelter slag

Abstract

This study investigated the use of copper smelter slag for the removal of phosphorus from secondary wastewater effluent through batch tests. The media was physically and chemically characterized and showed presence of Fe 2 O 3 (45.22%), SiO 2 (14.98%), Al 2 O 3 (3.21%), CaO (1.99%), SO 3 (1.77%) and MgO (1.33%). Scanning electron microscopy monographs revealed smooth and flat surface and no heterogeneity on the surface of the slag with visible micro pores before the experiment and less visible after the experiment. The point of zero charge of the media was 5.0. Equilibrium was reached after 4 h at 29.5 AE 0.71% phosphorus removal efficiency and media dosage of 0.4/100 mL. The kinetic data was best described by Pseudo second order equation. More than one mechanisms were involved in the adsorption of phosphorus onto copper smelter slag as suggested by multilinearity of intra particle diffusion model. Ninety seven percent (97.5 AE 0.0%) removal efficiency was achieved at an equilibrium dosage of 160 gL -1 . The equilibrium isotherm was described better by Langmuir equation with observed maximum adsorption capacity of 0.16 mg P g À1 media and the experimental maximum adsorption capacity was 0.26 mg P g À1 media. Regeneration studies showed low performance with maximum efficiency of 11.7% revealed during the first regeneration trial therefore low practical benefits. Copper smelter slag is a poor adsorbent for phosphorus and further studies on the media should be conducted.

Improvement of Phosphate Adsorption Kinetics onto Ferric Hydroxide by Size Reduction

“…The values of q max in Table 2 are better than the typical values for other by-products and wastes such as brick waste [8], copper smelter slag [9], or carbon waste [10] that usually range from 0.04 to 5.35 mg PO 4 3− /g. Red mud and commercial akaganeite [15,47], as well as commercial GFH [17,44], exhibit a similar range (26.8 to 39.6 mg PO 4…”

“…Pseudo second-order kinetics model (Equation ( 7)) could be linearized up to five different linear forms [36]. Regression using the linear form given in Equation ( 9) is the most used for phosphate kinetic studies [7][8][9][10]15]. This linear form could predict q e very well, but several references [36][37][38] indicate that this linearization could be inappropriate to obtain a good value of k 2 and the initial adsorption rate value (k 2 •qe 2 ).…”

“…Several Circular Economy approaches applied to the adsorption of phosphate have been considered in the literature. These alternatives include the recovery of phosphorus and water from several wastewater streams [1][2][3][4], the use of low-cost products or recovered waste as sorbents [5][6][7][8][9][10][11], and the study of the re-use of phosphate-loaded sorbents [2,3,[11][12][13]. To develop these strategies, it is paramount to optimize the performance of the sorption process.…”

Phosphorus and sulphates removal from wastewater using copper smelter slag washed with acid

“…A study by Letshwenyo and Sima [32] investigated the possibility of using the raw copper smelter slag for phosphorus removal from real wastewater. In this study, the same material was washed with a 2.0 M hydrochloric acid (HCl) solution and investigated for the removal of PO 4 3− P and SO 4…”

“…Previous studies on the characterisation of untreated copper smelter slag by [32] have shown various mineralogy and chemical contents of the material. The percentage content may have changed as some of the minerals may have reacted with the hydrochloric acid.…”