Online Cleaning of Carbonate Deposits. The Potential and Limitations of a Novel Cleaning Method

The formation of calcium carbonate scale within produced brine as it passes through topside heaters is a very common flow assurance challenge. Normally this scale risk is predicted and chemically controlled via scale inhibitors deployed upstream of the point of brine supersaturation. In some operations chemical application is not fully effective due to under treating of the chemical or carbonate from the reservoir (fines) builds up within the heaters. In cases of reduced fluid throughput cleaning of the inorganic scale is required. The most common method of cleaning is to take the heater offline and batch clean with acids (mineral or organic) to remove the deposits. This paper outlines an investigation into the performance of conventional batch cleaning vs a more novel application method of online cleaning the heater while operating with application of organic acid into the produced fluid upstream of the heaters. The online cleaning process was evaluated via laboratory tests where packed column of field scale were flushed with organic acid within the produced water, and for comparison mineral acid, to understand the potential for online cleaning vs batch cleaning and what factors influenced the effectiveness of these application methods. Factors evaluated included flow rate/contact time, acid strength and acid type. During these online cleaning tests, the effluent of each column was evaluated for pH and finally weight loss at the end of the tests. The online cleaning results were compared to conventional batch cleaning assessment of the same scale samples via static bottle tests The observations from the tests show that online cleaning using both organic and mineral acids result in the development of preferential flow paths within the scale packed columns that reduces the effectiveness of the cleaning chemicals. Improvements to the cleaning program were investigated such as the scale thickness when cleaning is first started to improve cleaning performance and fluid flow rate, increased acid concentration and liquid to solid ratio changes. Field application data from the initial cleaning programs and improvements to the cleaning programs will be shared as part of this publication The factors that need to be assessed to determine if this method is suitable for a specific process system and likelihood of effective scale removal are presented. This method does present the possibility for some production systems that cleaning of carbonate scale can be carried out without the need to take the heater offline for chemical batch or mechanical cleaning.

Bioinspired Cellulase-Mimetic Solid Acid Catalysts for Cellulose Hydrolysis

Glucose produced by catalytic hydrolysis of cellulose is an important platform molecule for producing a variety of potential biobased fuels and chemicals. Catalysts such as mineral acids and enzymes have been intensively studied for cellulose hydrolysis. However, mineral acids show serious limitations concerning equipment corrosion, wastewater treatment and recyclability while enzymes have the issues such as high cost and thermal stability. Alternatively, solid acid catalysts are receiving increasing attention due to their high potential to overcome the limitations caused by conventional mineral acid catalysts but the slow mass transfer between the solid acid catalysts and cellulose as well as the absence of ideal binding sites on the surface of the solid acid catalysts are the key barriers to efficient cellulose hydrolysis. To bridge the gap, bio-inspired or bio-mimetic solid acid catalysts bearing both catalytic and binding sites are considered futuristic materials that possess added advantages over conventional solid catalysts, given their better substrate adsorption, high-temperature stability and easy recyclability. In this review, cellulase-mimetic solid acid catalysts featuring intrinsic structural characteristics such as binding and catalytic domains of cellulase are reviewed. The mechanism of cellulase-catalyzed cellulose hydrolysis, design of cellulase-mimetic catalysts, and the issues related to these cellulase-mimetic catalysts are critically discussed. Some potential research directions for designing more efficient catalysts for cellulose hydrolysis are proposed. We expect that this review can provide insights into the design and preparation of efficient bioinspired cellulase-mimetic catalysts for cellulose hydrolysis.

Charcoal and Sago Bark Ash on pH Buffering Capacity and Phosphorus Leaching

Soil-available P for crop use is limited because of fixation reaction and loss of organic matter through erosion and surface runoff. These factors cause an imbalance between inputs and outputs of P nutrients in acid soils. Several approaches to improve P availability have been proposed, however, little is known about the effectiveness of amending humid mineral acid soils with charcoal and sago bark ash on P dynamics. Thus, pH buffering capacity and leaching studies were conducted to determine: (i) pH buffering capacity upon application of charcoal and sago bark ash and (ii) the influence of charcoal and sago bark ash on P leaching in acid soils. pH buffering capacity was calculated as the negative reciprocal of the slope of the linear regression (pH versus acid addition rate). A leaching study was carried out by spraying distilled water to each container with soil such that leachates through leaching were collected for analysis. The ascending order of the treatments based on their pH buffering capacity and regression coefficient (R2) were soil alone (0.25 mol H+ kg−1 sample), soil with charcoal (0.26 mol H+ kg−1 sample), soil with sago bark ash (0.28 mol H+ kg−1 sample), charcoal alone (0.29 mol H+ kg−1 sample), soil with charcoal and sago bark ash (0.29 mol H+ kg−1 sample), and sago bark ash alone (0.34 mol H+ kg−1 sample). Improvement in the soil pH buffering capacity was partly related to the inherent K, Ca, Mg, and Na contents of charcoal and sago bark ash. In the leaching study, it was noticed that as the rate of sago bark ash decreased, the pH of leachate decreased, suggesting that unlike charcoal the sago bark ash has significant impact on the alkalinity of leachate. Soil exchangeable acidity, Al3+, and H+ reduced significantly following co-application of charcoal and sago bark ash with ERP. This could be attributed to the neutralizing effects of sago bark ash and the high affinity of charcoal for Al and Fe ions. The amount of P leached from the soil with 100% charcoal was lower because charcoal has the ability to capture and hold P-rich water. The findings of this present study suggest that combined use of charcoal and sago bark ash have the potential to mitigate soil acidity and Al toxicity besides improving soil pH buffering capacity and minimizing P leaching. A field trial to consolidate the findings of this work is recommended.

The Application of Thermal Decomposition for Determination of Carbonate Acid-Neutralising Capacity for Improved Acid Mine Drainage Prediction

This study developed an industry-applicable, thermal decomposition methodology for quantification of carbonate mineral acid neutralisation capacity (ANCtherm-carb) for waste rock, tailings, and other mined materials. Standard titration-based methods for ANC can be compromised due to contributions from silicate minerals, ion exchange, Fe-rich carbonates, and other transition metal carbonates. C emission (CO2 and CO) was measured using IR in a N2 atmosphere. Cneut (wt%) was calculated using the C emission at 800 or 1000 °C minus the C emission at 400, 450 or 500 °C and the weight of sample prior to decomposition (Equation (2) of this manuscript). This value was then input into Equation (3) of this manuscript to calculate ANCtherm-carb. Good correlation of ANCtherm-carb for single-mineral carbonates with ANCcalc, calculated from bulk assay concentrations for Mg, K, Na, Ca, and Mn, was achieved. Thereafter, 18 waste rock samples were examined, resulting in the correlation of ANCtherm-carb versus non-standard ANCtitrate-carb (titration methodology adapted to focus on carbonate neutralisation only) with R2 = 0.96. This correlation is valid for samples containing both non-neutralising carbonates (siderite) and sources of neutralisation arising from non-carbonates (Mg-clay) within this waste rock system. Typically, mining operations use total C measurements for assessment of carbonate neutralisation potential in the block and mining model. This method provides an effective means to cheaply analyse for carbonate neutralisation potential with assignment of potentially acid-forming and non-acid-forming blocks to waste rock cells, etc.

Co-Application of Charcoal and Wood Ash to Improve Potassium Availability in Tropical Mineral Acid Soils

Potassium (K) is a macronutrient required by plants for energy production, enzyme activation, formation of cell wall, production of protein, and photosynthesis. However, K in the soil solution is leached from the rhizosphere before it interacts with soil colloids because of the abundance of kaolinite clay minerals in mineral acid soils such as Ultisols and Oxisols. These soils are highly weathered, low in organic matter, low in pH, but high aluminium (Al), and iron (Fe) ions. As a result, K becomes unavailable for plants, and this affects crop production and farmers’ profitability. This problem has steered the attention to the application of amendments to minimise K loss. Animal manures, plant residues, and composts applications are some of the corrective measures taken to improve the K availability in tropical acid soils. However, there is dearth of information on co-application of charcoal and wood ash as soil amendments to improve the K availability and the changes they cause to the dynamic equilibrium of K in mineral acid soils. Hence, this review discusses the dynamics, availability of K, and proposed mechanisms involved when charcoal and wood ash are used to amend tropical acid soils. The optimisation and understanding of the role of charcoal and wood ash co-application as soil amendments have potential benefits to improve the K availability and physicochemical properties of mineral acid soils.

Sulfonic Acid-Functionalized Inorganic Materials as Efficient Catalysts in Various Applications: A Minireview

Acid catalysis is widely used in the chemical industry, and nowadays many efforts are being focused on replacing the more common homogeneous catalysts with heterogeneous ones in order to make greener the industrial processes. In this perspective, sulfonic solid acid materials represent a valid alternative to the homogenous mineral acid in several acid catalyzed reactions. In this minireview, an overview of the recent advances on the preparation, stability and application of these materials is reported. Special attention is addressed to the sustainability of the considered processes, starting from the catalyst’s preparation, the use of green solvents and reducing the possible reaction steps. Ways to tackle the main drawback represented by easy leaching of acid groups are described. For an easy catalyst recovery, the use of a magnetic core in a catalyst particle, with the related synthetic approaches, is also illustrated. Finally, a section is dedicated to the principal characterization techniques to identify the structural properties of the catalysts.

Separation and Recovery of Gold(III), Palladium(II) and Platinum(IV) by Solvent Extraction Using a New β-Diketone Derivative from Acidic Solutions

This study indicates that a new amine derivative of β-diketone (EDAB-acac) can be successfully used in an acidic medium (HCl) to separate a mixture containing Au(III), Pd(II), and Pt(IV) ions using solvent extraction. The study was conducted in single and ternary model solutions. The impact of acid concentration and the type of solvent (toluene, chloroform, methylene chloride, 2-ethylhexanol) on separation efficiency was discussed. It has been shown that increasing the HCl concentration in the aqueous phase does not favor extraction. In contrast, solvents with high donor numbers (methylene chloride, 2-ethylhexanol) increase both the extraction percentage of Pd and Au as well as the separation coefficients of Pd in relation to Au and Pt. The palladium(II) and gold(III) (which form 4-coordinated planar [MCl4]2− complexes) are extracted most efficiently, Pd(II) (87–93%) and Au(III) (56–62%). The stripping of Au(III), Pd(II), and Pt(IV) ions from the EDAB-acac-methylene chloride phase was also investigated using 0.5 M ammonia aq., mineral acid (5 M HCl, 5 M HNO3), 0.1 M thiourea in HCl and 0.5 M ammonium thiocyanate. A 3-step stripping process was proposed for the recovery of Pd(II), Au(III), and Pt(IV) from the Pd-Au-Pt mixture in the EDAB-acac-methylene chloride system. In the first stage, the aqueous phase is treated with 5 M HNO3 (Pt separation), followed by the application of 0.5 M ammonia (Pd separation) and, finally, 0.1 M thiourea in HCl (Au separation). The solvent extraction with EDAB-acac in acidic medium (HCl) can be used for separation of Pd(II) and Au(III) ions from e-waste leach solutions.