Sustainable metal recovery from waste is of utmost importance. Zn is a micronutrient that is abundant in many industrial wastes. In this work, the process of converting industrial white pigment waste into a Zn micronutrient containing nitrogen fertilizers was developed utilizing an HNO 3 extraction method. For this purpose, solubility diagrams, polytherms, were constructed of the ternary CO(NH 2 ) 2 −Zn(NO 3 ) 2 −H 2 O and NH 4 NO 3 −Zn(NO 3 ) 2 −H 2 O systems to determine the corresponding phase equilibria and solid material chemical composition. Complex salts containing Zn and two and four urea molecules were observed and the catalytic Zn(NO 3 ) 2 effect was observed at the decomposition temperature of CO(NH 2 ) 2 during thermal analysis. Two crystalline phases of NH 4 NO 3 , namely III and IV, were observed and the corresponding transition temperature decreased with increasing Zn(NO 3 ) 2 concentration in solution. Zn extraction in the form of soluble Zn(NO 3 ) 2 was performed from the white pigment industrial waste and optimal extraction parameters including HNO 3 concentration, stoichiometric amount and temperature were determined. These included a 60°C solution temperature, 55% HNO 3 concentration and 140% of stoichiometric HNO 3 amount. This agreed well with the reactive conditions currently used in nitrophosphate fertilizer production potentially enabling direct production of micronutrient containing NP fertilizers without significant technology modification. Sensible compositions of UAN-28 and UAN-30 liquid fertilizers containing Zn micronutrient from industrial grade compounds and pigment waste extracted Zn(NO 3 ) 2 were obtained and their physicochemical properties were measured.

Design and manufacture of high nitrogen content sulfurcontaining fertilizers is of crucial importance in sustainable food and energy crop production. The availability of large elemental sulfur amounts in oil refining and natural gas processing facilities, in combination with decreasing sulfur deposition into soil from natural and anthropogenic sources in a bioavailable sulfate form, calls for innovative engineering solutions that bridge this gap via sustainable sulfur processing. Diurea sulfate-based liquid and compound solid granulated fertilizers were synthesized in this work, and their resulting physicochemical properties were determined. First, phase compositional information on the 2CO(NH 2 ) 2 ·H 2 SO 4 −CO(NH 2 ) 2 −H 2 O ternary system was measured, and high nitrogen content, ∼15:1 N:S ratio liquid fertilizer grades, were established. Next, diurea sulfate granulation experiments using (i) dolomite, (ii) byproduct material after the phosphoric acid extractive production, CaSO 4 ·0.5H 2 O, and (iii) dolomite combined with diammonium phosphate, (NH 4 ) 2 HPO 4 , and potassium chloride, KCl, were performed. Using diurea sulfate, 16−16−16−5.5(S)−0.4(MgO)− 0.6(CaO) compound granulated fertilizers were successfully obtained, and time-resolved changes in their crystalline phase composition during granule curing were monitored using XRD. The granule crushing strength measured increased to 3.800 MPa within the 30 day storage thus resulting in high quality fertilizer material.

Design and use of the adjustable N:P 2 O 5 ratio fertilizers is crucial in proper nutrient management if sustainable phosphorus use is to be ensured. Overfertilization with phosphorus can lead to its fixation in soil, as well as the unwanted environmental phenomena, such as eutrophication. Urea phosphate, CO(NH 2 ) 2 •H 3 PO 4 , based liquid fertilizers were synthesized in this work, and their resulting physicochemical properties were determined. For this purpose, phase composition information on the CO(NH 2 ) 2 •H 3 PO 4 −CO(NH 2 ) 2 −H 2 O ternary system was analyzed, and critical points on the polytherm were determined. Liquid fertilizer compositions were determined and their corresponding physicochemical properties established. Raman spectroscopy showed that CO(NH 2 ) 2 •H 3 PO 4 partially retains its strong bonding interactions between both molecular adducts in aqueous solutions suggesting their improved nitrogen management efficiency in soils. Effect of these acidic pH fertilizer solutions on the pH of soil was determined and was found negligible. The potential of these fertilizers for reducing the loss of nitrogen from the wet soil is also discussed.

Zinc containing organic materials were synthesized using dairy wastewater and solid zinc waste derived from zinc nitrate with the goal of obtaining biodegradable, slow release, micronutrient containing fertilizers. The developed synthesis procedure involved heating at mild 55 °C temperature, followed by pH adjustment to 7, precipitation, and drying. The resulting solid materials were characterized using weight analysis, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transformed infrared spectroscopy (FTIR). Higher wastewater-to-zinc nitrate ratios of 1: 1 / 5 yielded amorphous materials with no inorganic zinc compounds detected. TGA analysis showed very complex thermal behavior due to the large amount of organics present while FTIR analysis suggested the presence of both coordinated and uncoordinated carboxylic acid and ester groups. The developed process can have a variety of applications in recovering Zn from waste sources, such as tire crumb, while returning this valuable micronutrient into soil as a slow release biodegradable fertilizer.

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