Synergistic Removal of Zinc and Copper in Greenhouse Waste Effluent by Struvite

Abstract

Struvite (MgNH4PO4·6H2O) can be recovered from wastewaters for mitigation of phosphorus content. However, the interaction of dissolved constituents with struvite is rarely evaluated. Removal of heavy metals and total organic carbon (TOC) in a greenhouse wastewater (GW) by struvite was investigated. Presynthesized struvite was added to GW and removal of Zn (689 μg/L), Cu (151 μg/L), and TOC (51 mg/L) monitored from 1 to 26 d. Metal uptake in sodium nitrate solutions was used to assess competition, and the influence of other GW constituents on sorption. Struvite was also directly precipitated from GW (PPT). Recovered GW solids had 64–247 mg/kg Zn, 12–54 mg/kg Cu, and 1721–8806 mg/kg TOC, with lowest loadings for PPT and highest for 26 d solids. X-ray absorption spectroscopy detected polymerized Zn-phosphate, induced by dissolved phosphorus in GW, and Cu copolymerization, initially limited by aqueous Cu-organic complexation. Sorbed Cu shifts Fourier transform infrared-sensitive phosphate bands and changes the intensities of reflections in X-ray diffraction patterns of struvite more so than Zn. Struvite from GW is more susceptible to thermal decomposition than unreacted struvite, evolving CO­(g), CO2(g), NH3(g), and H2O­(g). Therefore, struvite from GW sorbs metals and organics, and can release sorbed and structural components to the aqueous and gas phases.

Aerated Fluidized Bed Treatment for Phosphate Recovery from Dairy and Swine Wastewater

“…Qualitative evaluation of FTIR spectra of aerated-FBR solids (Figure ) supports findings from P removal experiments and XRD analysis. Struvite has characteristic vibrations centered at 992 and 1432 cm –1 associated with the ν 3 PO 4 3– , and ν 4 NH 4 + bands. − Calcite bands are located at 712, 875, and 1382 cm –1 , for the ν 4 , ν 2 , and ν 3 CO 3 2– vibrations . The S-WW and S-model-35 FTIR spectra were similar to the struvite standard spectrum, consistent with the >90% struvite content detected by XRD.…”

“…Similarly, higher carbonate concentration yielded higher calcite content for D-WW solids. The presence of trace elements in the solids is attributed to their build up through sorption by struvite − and/or calcite. This process increased the trace element concentrations of the solids, even from the model solutions which had initial concentrations below ICP-OES detection limits.…”

“…The S-WW and S-model solids had a TG mass loss typical for struvite, , except for S-model-15 that displayed the additional mass loss step for calcite (Figure a, Figure S6). The D-WW and D-model solids have a two-step mass loss at 120–180 and 250–500 °C.…”

Struvite Crystallisation and the Effect of Co2+ Ions

“…Common contaminants present in wastes include heavy metals and metalloids, such as chromium (Cr), zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), arsenic (As), and selenium (Se), as well as various organic substances and pathogens. During struvite precipitation, these species could either be incorporated in the struvite structure, adsorbed to the crystal surface, or precipitated as separate phases [9][10][11][12][13]. Thus, such ions likely affect the crystallisation behaviour of struvite.…”

Study of Struvite Crystal Growth with The Addition of Tartaric Acid

“…pH is an important factor in the formation of struvite crystals because it affects the solubility and thermodynamic properties [3]. To reduce struvite crystals as crystalline scales in general use inorganic additives Cu 2+ and Zn 2+ [4,5], Cu 2+ , Pb 2+ and Zn 2+ [6] or organic additives malic acid [7], carboxylic acid compounds [8], citric acid [9] , maleic acid [10] which can inhibit the growth of struvite crystals. In previous studies, three carboxylic acids (citric acid, tartaric acid and maleic acid) were used as * Corresponding author : saridyah05@gmail.com effective inhibitors even at low molar concentrations [8].…”