Recovering phosphorus as struvite from anaerobic digestate of pig manure with ferrochrome slag as a magnesium source.

The circular economy initiative has driven the agriculture and agro-based industry to beneficiate from waste,thus closing the material loop towards enhancing economic and environmental performance. In this study, the aim was to recover phosphorus from anaerobic digestate of piggery wastewater (ADPW) using ferrochrome slag (FCSL) as the magnesium source to improve the environmental and economic sustainability of struvite precipitation. This was achieved by leaching 100 g L-1 of ferrochrome slag with 5 M HCl where 14.02 g L-1 of magnesium ions were extracted, and this acid-leachate of ferrochrome slag also contained 2650 mg L-1 of total iron. To simultaneously remove both high concentrations of organic matters in ADPW and iron in FCSL which are known to be detrimental to struvite precipitation, hydrogen peroxide (H2O2) at an H2O2/Fe molar ratio of 0.75 and pH 4.0 was added to the mixture of ADPW and FCSL. After the Fenton reaction, removal efficiencies of chemical oxygen demand (COD) and total iron reached 95.06% and 94.00%, respectively. Then COD and an iron-reduced mixture of ADPW and FCSL were added with a satisfying Mg:N:P molar ratio of 1.2:1:1.15 at pH 9.5 to produce struvite in 1 h. From 1 L of ADPW (2.6 g NH3-N), 0.5 L of FCSL (5.34 g Mg2+), and 6.62 g of PO4 3- P, were consumed to produce 45.57 g of struvite precipitate. Additionally, the economic feasibility of ferrochrome slag was assessed by estimating the chemical costs of FCSL against that of magnesium chloride which is commercially used. It was observed that using FCSL was cheaper as compared to using commercial MgCl2. Response surface methodology coupled with the central composite design was applied as a statistical tool to determine the effects of the key parameters (N:P; Mg:PO4; pH) on phosphorus recovery. Second-order polynomial equations were determined to correlate the parameters. ANOVA was applied and showed that p values for all the investigated parameters were less than 0.05 showing that they had a statistically significant effect on the phosphorus recovery. The study confirmed that it was possible to recover phosphorus as struvite from anaerobic digestate of pig manure with ferrochrome slag as a magnesium source.

Magnesium recovery from ferrochrome slag: kinetics and possible use in a circular economy.

The ever-increasing demand for ferrochrome alloys has resulted in a substantial accumulation of ferrochrome slag by-products in many mining areas. On the other hand, the ferrochrome slag has been identified as one waste material that is rich in magnesium (Mg) and has not been effectively exploited. Beneficiating of ferrochrome slag (FCS) waste material is envisaged as a means of achieving sustainable recovery of Mg. Previous studies have used sulphuric acid as a lixiviant for leaching FCS at moderate temperatures to recover Mg. In this study, the recovery of Mg from ferrochrome slag was investigated using hydrochloric acid (HCl) as the lixiviant at low temperatures. Previous studies have shown that various metal oxides have been proven to be more amenable to leaching using HCl. This study examined the effects of acid content, leaching temperature, and reaction time on the recovery of Mg from FCS. Kinetic and thermodynamic analysis of the leaching process were also investigated as these are critical factors for maximum extraction of the Mg. The results showed that the highest recovery of Mg of 88.2% was obtained from FCS using 5 M HCl with a solid to liquid ratio of 1:10, mixing intensity of 250 rpm, reaction time and temperature of 150 min and 70 °C, respectively. The shrinking core model (SCM) was used in kinetic analysis to find the experimental data's best fit. A linear relationship was obtained with the coefficient of determination for the chemical reaction model (Kc) of >0.9 which indicates a good fit. The activation energy obtained for the diffusion and chemical reaction models were 95.44 and 41.45 kJ/mol, respectively, demonstrating that the rate-limiting phase is the one involving the chemical reaction.

Biological acidification of pig manure using banana peel waste to improve the dissolution of particulate phosphorus: A critical step for maximum phosphorus recovery as struvite.

Traditional disposal of agricultural bio-waste such as pig manure and banana peel waste poses an environmental nuisance. The uncontrolled disintegration of these waste materials decomposes to toxic effluent and methane a greenhouse gas twenty-one times more potent than carbon dioxide at trapping heat in the atmosphere, which is detrimental to the climate by elevating temperatures. Agricultural bio-waste is rich in nutrients that include nitrogen and phosphorus. Selectively separating these nutrients from the solid phase to produce high value products has been envisaged as an effective method of waste valorisation. This study aims to investigate the solubilisation of phosphorus (P) during anaerobic digestion (AD) of pig manure with banana peel waste as the co-substrate. The objective was to enhance the biological dissolution of the phosphorus from solid pig manure to the aqueous phase as this is envisaged to subsequently ease the recovery of P as a concentrated product via crystallization. Thereafter, phosphorus is used as a slow-release mineral fertilizer. Biological acidification was effective in reducing the pH to less than 6.50 from an initial pH of 7.28 at higher doses of BPW >100 g/L. Maximum dissolution of total phosphorus of 75% was observed at a pH of 5.40. Multiple regression analysis was used to correlate pH, banana peel waste concentration, and the anaerobic digestion time (ADT) to optimize the dissolution of P as this was deduced to be occurring at a low pH. A 2nd order polynomial was deduced to best fit the data with an R2 value of 0.90. The p values for the HRT and banana peel waste concentration were both <0.05 showing that both variables had a strong influence on the pH.

Optimization of pulp production from groundnut shells using chemical pulping at low temperatures.

Paper production through chemical pulping has been identified as one of the ideal avenues of exploring the uses of groundnut shells as they are rich in cellulose. Ideally, the cellulose can be used to synthesize fibres that can be converted into useful paper products. In this study, chemical pulping was the chosen process for liberating the fibres as it is effective in dissolving lignin embedded within the cellulose. In addition, the fibres produced have superior physical properties compared to mechanical pulping. It is imperative that optimal conditions are identified for the chemical treatment process, in order to ensure that energy and chemical consumption are minimized. All these measures are aimed at reducing production costs and make chemical pulping economically viable, as compared to the mechanical pulping process which is less costly. Response surface methodology (RSM) was used in this study to evaluate the effect of three independent variables (cooking time, temperature, and sulphidity) on pulp yield and kappa number. These parameters are critical in the chemical pulping process and the optimal conditions obtained were 180 min, 100 °C and 23.6 wt.%, respectively. At the optimal cinditions, the pulp yield was 64.39wt% with a kappa number of 19.5. The results showed that all parameters investigated, had a statistically significant effect on the production of pulp. The increased cooking time was efficient in ensuring complete impregnation of the groundnut shells with chemicals for pulping and ensuring that the dissolution of lignin is not selective and does not result in dead spots inherently compromising the quality of the pulp. On the other hand, lower temperatures limited the peeling effect due to hydrolysis of carbohydrates which increased pulp yield due to a higher cellulose retention. Consequently, this contributed towards obtaining pulp that is well cooked, has a low bleach consumption and a higher quality.

Structure of a radiate pseudocolony associated with an intrauterine contraceptive device.

Transmission electron microscopy of a radiate pseudocolony associated with an intrauterine contraceptive device (IUCD) showed central bundles of extracellular fibers averaging 35 nm in diameter, surrounded by layered mantles of electron-dense, amorphous granular material. No bacterial, viral, or fungal structures were present. X-ray microanalysis revealed copper, sulfur, chloride, iron, and phosphorus; no calcium was found. It is postulated that these structures and histologically identical non-IUCD-associated granules from the female genital tract, as well as similar structures from other body locations, including those reported in colloid cysts of the third ventricle, are of lipofuscin origin.

Pseudo-sulfur granules associated with intrauterine contraceptive devices.

A structure resembling a sulfur granule found in histologic sections of endometrium from patients with intrauterine contraceptive devices is described. It is distinguished from a true sulfur granule on morphologic grounds and is further characterized as a foreign substance, most probably fragments of the synthetic contraceptive device. It is not associated with clinical disease. Microbiologic cultures of removed intrauterine contraceptive devices show no consistent or predominant growth pattern.

PIP: Microscopic slides of 235 samples of endometrial curettings obtained when an IUD was removed were reviewed for the presence of sulfur granule-like structures and IUD-associated material. Where such structures were present, the following stains were done: Gram, Ziehl-Neelsen, periodic acid-Schiff, Grocott's modification of Gomori's methenamine silver, and von Kossa's stain for calcium. A prospective study was conducted in an effort to determine a possible microbiologic origin of the "granules." 50 IUDs removed at the time of dilatation and curettage were cultured. The technics used are described. In 235 endometrial samples examined histologically, 17, or 7.2%, showed the presence of granular structures. 1 true actinomycotic granule was identified. There were 16, or 6.8%, examples of pseudo-sulfur granule; 71 endometria (30%) contained IUD-associated material. All of the pseudo-sulfur granules were found in samples containing the IUD-associated material. The finding of IUD associated material and granules was not related to the type of IUD that was removed. On histologic examination, the most common type of sulfur granule-like structure found showed a glassy eosinophilic color, a radiate appearance, and peripheral clubbing. 14 (28%) of the IUDs cultured yielded no growth, and 17 (34%) grew normal vaginal flora. 19 of the cultures yielded a variety of organisms not normally considered part of the vaginal flora; there was no association with a particular type of IUD. Of the 50 IUDs cultured, 3 had pseudo-sulfur granules in the histologic sections of the corresponding endometrial curettings. 33% of patients with pseudo-sulfur granules and 52% of patients without these granules sought removal of the IUD because of symptoms. The most common type of granule encountered is classified as a psuedo-sulfur granule and is nonpathogenic.

Evaluation of contrast markers for CT aspiration biopsy.

Precision percutaneous needle aspiration biopsy under guidance of computed tomography is facilitated by injection of a small amount of contrast material during the biopsy procedure. CT scan immediately after biopsy clearly documents the biopsy site. There was no adverse effect of the contrast agents on the quality of staining or preservation of cellular architecture. To the contrary, the aspirates obtained after contrast injection were generally better preserved and better stained than the control specimens. This may be due to a decrease in drying, with the more fluid aspirates obtained after contrast injection.