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Reactive silica additives, such as clays, can increase the filterability of phosphogypsum (PG) during wet phosphoric acid production from phosphate rock (PR). In this study, the effect of adding inexpensive fly ash waste (34 kg per t PR) together with lower quantities of pure silica (8.5 kg per t PR) on the radioactivity of PG was investigated. The addition of fly ash waste/pure silica reduced the radiological activity of the PG by roughly 30%. The reduction was attributed to decreased activities from 238U (60% reduction) and 226Ra (30% reduction) in PG. Besides, P2O5 losses were slightly decreased. [ABSTRACT FROM AUTHOR]

During the calcination of magnesium ammonium phosphate hexahydrate (struvite) in the process of recycling to obtain phosphoric acid, ammonia is released in addition to water and carbon dioxide. With a gas scrubber, e.g., in the form of a bubble column reactor, ammonia can be recovered as a usable valuable material. With water as an inexpensive and effective absorbent, almost complete absorption (92 %) of the ammonia from the exhaust air can be achieved. [ABSTRACT FROM AUTHOR]

Petrochemical catalysts are widely used in the industry. For the production of cumene, zeolite‐based catalysts containing phosphoric acid are applied. Over the time, coking deactivates the surface, and the catalyst has to be exchanged and disposed of. Different process approaches for recycling the phosphoric acid‐containing catalysts were investigated. Related preliminary investigations have shown that calcination of the used catalyst is necessary prior to reprocessing. By digesting the catalyst with hydrofluoric acid, ∼96 % phosphate was recovered. However, this process is very costly in terms of process technology. More promising is digestion by basic or acidic routes. Several options are possible here, and digestion with H3PO4 proved to be particularly suitable. Here, phosphate yields reached up to 98.8 %, with a positive balance of economic efficiency at the same time. The catalyst can be produced and recycled in the same plant with the same reagents, what constitutes a major breakthrough towards sustainability in industrial catalysis. [ABSTRACT FROM AUTHOR]

• Purification of phosphoric acid by cross-flow solvent extraction process. • Iron(III) removal from crude phosphoric acid using Cyanex 572 as extractant. • A valuable product like REO is obtained after valorization of the recovered REEs. • Optimized phosphoric acid production developing climate-friendly process. Phosphoric acid produced from phosphate rock is an intermediate product in mineral fertilizer production. Purification stages are commonly used to extract unwanted elements such as iron associated with the phosphate rock after the initial wet acid treatment. The current work presents a process that extracts iron(III) and recovers high-value rare earth elements (REEs) during phosphoric acid purification. A cross-flow solvent extraction process with four stages is used and a final raffinate with 684 mg/L P without losses during the process is obtained. Iron(III) removal (98.1 ± 0.7%) was achieved after the first two stages using Cyanex 572 as extractant. The metal loaded was fully stripped using 2 mol/L HCl with a single-stage reaching a solution purity >99.8%. 96.6 ± 1.2% REEs were subsequently recovered by Cyanex 923 in the next two solvent extraction stages. Water as a strip solution was used to re-extract these valuable metals from the organic phase. The purity of the aqueous solution was >99.6%. The study presents a promising approach in which a single technique was utilized for phosphoric acid purification and valuable byproduct recovery that next needs to be tested under industrial conditions. [ABSTRACT FROM AUTHOR]

Phosphorus is a vital component of fertilisers – and a growing global population relies on a stable supply of agricultural produce. Endeavours to recycle phosphates from sewage sludge ash (SSA) have so far been limited by lacking understanding of material associations and the actual phosphate compounds in SSA. Owed to the high amorphous content of ashes, unlike X-ray diffractometry (XRD), automated mineralogy systems (MLA here) allow for a deeper study of phosphate-bearing phase associations in ashes. An intricate knowledge of target resource association is crucial for efficient recycling: this applies to all target products, elemental P, phosphoric acid or recycled fertiliser. Failing to understand these morphologies and target associations will inevitably lead to inefficient processes – perhaps even close off this resource completely. Thus, phase studies add to all P-recovery approaches from sewage sludge ashes. Sludge of three German cities has been incinerated under the same conditions and sampled, thus enabling an analysis of ash characteristics. [ABSTRACT FROM AUTHOR]

• Khouribga PR shows relevant REE (577 ppm) and Y (240 ppm) concentrations. • The majority of REE (<80%) and Y (<70%) transfer to the solid PG stream. • Recovering REE and Y from solid PG is economically challenging. • Fly-ash/pure silica additives increase REE and Y transfer to the liquid PA stream. Adding active silica (SiO 2) to reduce the free fluoride content is a known method to improve the filterability of phosphogypsum (PG) during wet phosphoric acid (WPA) processing of phosphate rock (PR). Besides, this process can also promote the transfer of valuable rare earth elements (REE) from the PR into the liquid phosphoric acid (PA) stream rather than into the solid PG matrix from which later economic recovery is more challenging. Khouribga PR, that shows total REE concentrations of 577 ppm (328 ppm heavy REE and 249 ppm light REE) of which yttrium (Y) with 240 ppm constitutes the major fraction, is processed at the Jorf Lasfar El-Jadida chemical complex in Morocco that is also home to the country's largest coal power plant. Fly ash produced during thermal power production, 70% of which is stacked in the immediate vicinity, presently remains mostly unused and consists largely (48%) of silica. In this work the use of fly ash (34 kg per t PR) and pure silica (8.5 kg per t PR) on the transfer of REE from Khouribga PR into the PA and PG stream during dihydrate WPA production was examined. The inexpensive fly ash/silica additive increases the transfer of various REE to the PA stream. For Y an increase of 37% was measured that resulted in a concentration of 48 ppm in the PA stream prior to further concentration by evaporation. [ABSTRACT FROM AUTHOR]

• Argan nutshells were ground to sawdust and used in packed column experiments. • The sawdust successfully adsorbed U from synthetic solutions. • The sawdust absorbed 54% of U and 75% of Cd from merchant-grade PA. • Direct heavy metal recovery using argan nutshell sawdust is not reasonable. • Heavy metal extraction using argan nutshell sawdust and later recovery is promising. Argan nutshells, available in Morocco as a low-cost by-product from Argan oil production, were used to produce a sawdust biosorbent for the extraction of U and other heavy metals (Cd, As, Zn, Cu, Ni and Cr) from merchant-grade phosphoric acid (PA). Packed column (D = 20 mm, L = 250 mm, flowrate 1 mL/min) lab-scale experiments were carried out with three different solutions: (1) a synthetic heavy metals solution, (2) pure PA at different concentrations (0.85%, 8.5% and 85%) in water, and (3) merchant-grade PA from an industrial fertilizer plant in Morocco that was diluted with water to analyze different P 2 O 5 contents (5%, 30% and 54%) and a U concentration of up to 157 ppm. The sawdust successfully adsorbed 99% of the U from (1) the synthetic solution and (2) the pure PA independent of the acid concentration. It further managed to adsorb more than half (54%) of U, 75% of Cd, 74% of As, 84% of Zn, 86% of Cu, 83% of Cr of the merchant-grade PA at 54% P 2 O 5 content and a flow-rate of 1 mL/min. The sawdust was characterized by SEM and FTIR to understand the adsorption of metal ions. Column studies were carried out to know the breakthrough point. At breakthrough, the effluent volume was found to be 50 mL and the maximum adsorption capacity for U was found to be 0.93 mg/g. Heavy metal recovery using ANS does not seem to be promising as a result of the low (>10%) desorption rates if citric- or oxalic acid is used as was done in this study. Heavy metal extraction without direct recovery using ANS is promising and should further be investigated though. [ABSTRACT FROM AUTHOR]