Lime Dosage Research Articles

Study on Machine Learning-based Prediction of Lime Dosage for Mine Drainage Treatment

Study on Machine Learning-based Prediction of Lime Dosage for Mine Drainage Treatment

Revealing the interplay of dissolved organic matters variation with microbial symbiotic network in lime-treated sludge landscaping

Lime pretreatment is commonly used for sludge hygienization. Appropriate lime dosage is crucial for achieving both sludge stabilization (lime dosage >0.2 g/g-TS) and promoting plant and soil health during subsequent landscaping (lime dosage <0.8 g/g-TS). While much research has been conducted on sludge lime treatment, few studies have examined the effects of lime dosing on integrating sludge stabilization and plant growth promotion during landscaping. In this study, we investigated microbial dynamics and dissolved organic matter (DOM) transformation during sludge landscaping with five lime dosage gradients (0, 0.2, 0.4, 0.6, 0.8 g lime/g-TS) over 90 days. Our results showed that a lime dosage of 0.4 g/g-TS is the lower threshold for achieving waste activated sludge (WAS) stabilization during landscaping, leading to maximum humic substance formation and minimal phytotoxicity. Specifically, at 0.4 g/g-TS lime dosage, protein degradation and decarboxylation-induced humification were significantly enhanced. The predominant microbial genera shifted from Aromatoleum to Exiguobacterium and Romboutsia (both affiliated with the phylum Firmicutes). Reactomics analysis further indicated that a 0.4 g/g-TS lime dosage promoted the hydrolysis of proteins (lyase reactions on C-C, C-O, and C-N bonds), amino acid metabolism, and decarboxylation-induced humification (e.g., C1H2O2, C2H4O2, C5H4O2, C6H4O2). The co-occurrence network analysis suggested that the phyla Firmicutes, Proteobacteria, and Bacteroidetes were key players in DOM transformation. This study provides an in-depth understanding of microbe-mediated DOM transformation during sludge landscaping and identifies the optimal lime dosage for improving sludge landscaping efficiency.

Impact of Dolomite Liming on Ammonia-Oxidizing Microbial Populations and Soil Biochemistry in Acidic Rice Paddy Soils

Background and Aims: Over the last few decades, rampant nitrogen fertilization has exacerbated soil acidification in agricultural ecosystems. To counteract this, liming has become an essential technique for rehabilitating fertility in acid-degraded agricultural soils. Our research aimed to shed light on the response of ammonia oxidizers to liming in acidic soils within a controlled rice paddy experiment. We conducted a pot experiment with rice, featuring three different treatments: a control with only soil, a low dolomite dose (LD), and a high dolomite dose (HD). Various soil properties were investigated throughout the study. Under flooding, soil pH values rose across the treatments, from 5.4 in the control to 6.8 in HD. Ammonium and nitrate levels peaked in the HD treatment, reaching 30 and 22 mg kg−1, respectively. Similarly, dissolved organic carbon and microbial biomass carbon surged at mid-season aeration, hitting highs of 101 and 30 mg kg−1, respectively, in the HD treatment. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) were responsive to dolomite-lime application, with distinct reactions; AOB abundance and potential nitrification rates were positively affected by higher lime doses, whereas AOA numbers decreased over time and with dolomite application. Additionally, soil enzymes such as urease, catalase, invertase, phenol oxidase, and phosphatase also increased progressively, mirroring the rise in soil pH. This study identified increased soil pH as the critical factor influencing various soil parameters, especially the balance between AOA and AOB populations. Both AOB and AOA were sensitive to liming; AOA decreased while liming stimulated AOB abundance.

Application of soil amendments to reduce the transfer of trace metal elements from contaminated soils of Lubumbashi (Democratic Republic of the Congo) to vegetables

The extraction of copper and cobalt from mines has led to the contamination of agricultural soils by trace metal elements (TMEs) (e.g. Cu: 204 to 1355 mg/kg). The mining industry is one of the sources of metal discharges into the environment, contributing to water, soil, and air contamination and causing metabolic disorders in the inhabitants of the city of Lubumbashi (R.D. Congo). This study assessed the effectiveness of organocalcareous soil improvers applied to TME-contaminated soils to reduce their transfer to plants. Following a factorial design, increasing doses of organic soil improvers (chicken droppings and sawdust) and agricultural lime were applied to the soils of three market gardens (high, medium, and low Cu contamination). The experiment was monitored for 60 days. Soil physicochemical properties (pH, TOC, and total and available copper, cobalt, lead, cadmium, and zinc (mg/kg)) were determined for the three gardens and in the vegetable biomass. The daily consumption index of the vegetables was determined based on total TME content. The results show that organocalcareous soil improvers did not promote plant growth and survival on soils with high and medium levels of copper contamination. However, on soils with low copper content, organocalcareous soil improvers improved germination and plant survival and reduced the transfer of metals from the soil to the plants. The best germination and plant survival rates were obtained with the lightly contaminated market garden. In addition, the organo-limestone amendments applied to the soils slightly increased the soil pH from acidic to slightly acidic, with pH values ranging from (5.43 ± 0.07 to 7.26 ± 0.33). The daily vegetable consumption index obtained for cobalt in the low-contaminated garden ranged from (0.029 to 0.465 mg/60 kg/day), i.e. from 0.5 to 8.45 times higher than the FAO/WHO limit, unlike the other trace metals (Cd, Cu and Pb) for which the daily consumption index found was lower than the FAO/WHO limit. Organocalcareous soil improvers can only be applied to soils with low levels of TME contamination, but for soils with medium to high levels of metal contamination, new soilless production techniques such as hydroponics or bioponics are needed.

Optimization of Ammonia Removal from Landfill Leachate by Aeration Using Response Surface Methodology (RSM)

Landfill leachate has a high concentration of ammonia, making it a harmful pollutant for both surface and groundwater. One of the most favoured methods for removing ammonia from leachate is aeration, as it has been proven to remove a significant amount of ammonia in the most efficient and economical way. The effect of operational variables on ammonia removal efficiency by aeration was investigated in the current study by applying Response Surface Methodology (RSM) approach. Three operating parameters such as airflow rate, aeration time and lime dosage were investigated to achieve the optimization of ammonia removal. The optimal parameters for a favourable reaction of ammonia-nitrogen (NH3N) removal were found to be 6 L/min airflow, 90 minutes aeration time, and a lime dosage of 6 g/L. At these ideal conditions, Quadratic RSM predicted a maximum NH3N removal of 98.0%, which has been validated by the experiment and successfully removed 97.6%. The finding also showed that airflow rate and aeration time were more significant than lime dosage for NH3N removal. Due to increased contact time between air and liquid, regardless of the amount of lime used, increasing the aeration period ammonia removal efficiency. Considering the influential factors, determining the optimum condition for ammonia removal by aeration will explain the potential interferences that may inhibit the efficient recovery of NH3N. Hence, aeration is a promising approach for ammonia removal from landfill leachate.

Optimization of Ammonia Removal from Landfill Leachate by Aeration Using Response Surface Methodology (RSM)

Landfill leachate has a high concentration of ammonia, making it a harmful pollutant for both surface and groundwater. One of the most favoured methods for removing ammonia from leachate is aeration, as it has been proven to remove a significant amount of ammonia in the most efficient and economical way. The effect of operational variables on ammonia removal efficiency by aeration was investigated in the current study by applying Response Surface Methodology (RSM) approach. Three operating parameters such as airflow rate, aeration time and lime dosage were investigated to achieve the optimization of ammonia removal. The optimal parameters for a favourable reaction of ammonia-nitrogen (NH3N) removal were found to be 6 L/min airflow, 90 minutes aeration time, and a lime dosage of 6 g/L. At these ideal conditions, Quadratic RSM predicted a maximum NH3N removal of 98.0%, which has been validated by the experiment and successfully removed 97.6%. The finding also showed that airflow rate and aeration time were more significant than lime dosage for NH3N removal. Due to increased contact time between air and liquid, regardless of the amount of lime used, increasing the aeration period ammonia removal efficiency. Considering the influential factors, determining the optimum condition for ammonia removal by aeration will explain the potential interferences that may inhibit the efficient recovery of NH3N. Hence, aeration is a promising approach for ammonia removal from landfill leachate.

Exploring sustainable solutions for soil stabilization through explainable Gaussian process-assisted multi-objective optimization

The adoption of sustainable solutions in soil stabilization has piqued the interest of the scientific community due to the potential reduction in carbon footprint. In this regard, the research community has started looking for the alternate sustainable solutions to limit the quantity of conventionally used ecologically unfriendly soil stabilizers like lime and cement by utilizing the agricultural and industrial by-products. The production of conventional soil stabilizers (lime and cement) is extremely energy-intensive and contributes tons of greenhouse gases to the atmosphere. In general, evaluating suitability of these additives requires in-lab investigation of soil samples with varying additive concentrations and curing periods, making this approach both resource and time-intensive. Hence, this article proposes a computational framework for accelerated characterization of soil-stabilization by using the coupled experimental-Gaussian process (GP) based machine learning (ML) model. The dataset utilized for constructing the GP models consists of input features such as the stabilizer content (lime and rice husk ash (RHA)), coir fiber content, and curing period (measured in days). The target responses are the strength measures of the stabilized soil, such as unconfined compressive strength (UCS), split tensile strength (STS), and California bearing ratio (CBR). The proposed computational framework is deployed to perform multi-objective genetic algorithm (MOGA)-based optimization to achieve maximum engineering performance from stabilized soil. The presented study demonstrated that with the optimal dosage of rice husk ash (agricultural by-product), and cashew nut shell liquid (CNSL) treated coir fiber, the requirement for lime dosage may be significantly reduced while maintaining the engineering performance of the soil. The presented computational framework can be extended to any construction practices for ensuring the strategic selection of the control variables for optimizing the desired performance.

The influence of the pre-addition of semi-dry and dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of MSWI fly ash

Incineration is a main way to dispose the municipal solid waste (MSW) in China, but municipal solid waste incineration (MSWI) fly ash will negatively impact the environment and human health as containing high content of heavy metals. This study aimed to investigate the influence of the pre-addition of dry/semi-dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of fly ash. This study has found that semi-dry slaked lime had more effect on the solidification rate of heavy metals in MSWI fly ash compared to the pre-addition of the dry slaked lime. As the dosage of semi-dry slaked lime increased, the solidification rate of Zn and Ba increased to 100 %, while the solidification rate of Cr decreased to as low as 0 %. However, the effect of the dosage of semi-dry slaked lime on the other heavy metals (Cu, Pb, Cd, Ni) showed a complex trend. This study underscores the importance of the pre-addition of slaked lime during the purification of flue gas in influencing subsequent chelation and solidification treatment of MSWI fly ash. It provides valuable insights into optimizing lime dosage to enhance heavy metal stabilization, contributing to more effective and sustainable waste management practices.

Effect of lime on soil chemical properties and corn growth in Ultisols Lebak, Banten

Abstract The research aimed to study the effect of lime on soil chemical changes and corn growth in Ultisol Lebak, Banten. The soil used is acidic mineral soil with a pH of 4.8 and a high exchangeable (exch) Al content of 6.3 cmolc kg−1. The research design used was a completely randomized design with 6 treatments of lime doses with 5 replications. The dose of lime applied is based on exch Al namely 0, 0.5; 1.0; 1.5, and 2.0 equivalent to 0, 3, 6, 9, and 12 t ha−1, respectively, and 1.0 exch Al of fosfatan. The results showed that lime application improved soil chemical properties as reflected by increasing soil pH, exch Ca, Mg, cation exchange capacity (CEC), base saturation (BS), and decreasing Al content and saturation. In addition, lime application increases the delta of soil pH. Soil acidity (pH) increased from 4.8 to 6.3; exch Ca levels increased from 1.61 to 12.77 cmolc kg−1, exch Mg levels increased from 0.78 to 0.88 cmolc kg−1.

Lime and Gypsum Rates Effects in New Soybean Areas in the Cerrado of Matopiba, Brazil

High rates of limestone have been increasingly utilized in newly converted areas for grain production in agricultural frontier regions to expedite the short-term correction of soil fertility, leading to compensatory yields. However, there is a lack of information about different doses of lime and gypsum for soils in the Cerrado of Matopiba, especially in the state of Piauí, Brazil. The aim of this study was to evaluate the effects of doses of lime and gypsum in newly converted areas for soybean production in the Cerrado of Southwest Piauí. The study was carried out in the 2019/2020 and 2020/2021 crop years, on yellow Oxisol soil, in a randomized block design and treatments following a 5 × 4 factorial: five lime rates (0, 5, 10, 15, and 20 t ha−1) and four gypsum rates (0, 1, 2 and 4 t ha−1), with four replicates. The standard lime and gypsum rates were 5 t ha−1 and 1 t ha−1, respectively. Soil fertility attributes (0.0–0.2, 0.2–0.4, and 0.4–0.6 m), nutritional status of plants, and soybean yield were measured. The increases in grain yield using a lime rate of 10 t ha−1 were 18% and 12% in the 2019/2020 and 2020/2021 crop years, respectively. High lime rates provide a reduction in the concentrations of P, K, and cationic micronutrients in soil, thereby reducing leaf contents of macro- and micronutrients in soybean plants. Concentrations of Ca, Mg, and S in subsurface layers were raised to proper levels, similar to those recommended for topsoil (0.0–0.2 m). The use of gypsum and lime in newly converted areas for soybean cultivation provides quick improvement in soil chemical conditions and reduction in acidity components. The application of 10 t ha−1 of lime improved the soil chemical environment in the Matopiba region the short time available for chemical reactions to occur, allowing soybean cultivation in newly converted areas of Cerrado into agriculture.

Efficient recovery of highly pure CaF2 from fluorine-containing wastewater using an icy lime solution.

Developing a feasible and low-cost strategy for the recovery of calcium fluoride efficiently from fluoride-containing wastewater is very essential for the recycle of fluoride resources. Herein, a modified lime precipitation method was employed to recover CaF2 from fluorinated wastewater using a special icy lime solution. Intriguingly, the highest F- removal was greater than 95% under the optimal condition, leaving a fluoride concentration from 200 to 8.64 mg/L, while the lime dosage was much lower than that of industry. Importantly, spherical-shaped CaF2 particles with a 93.47% purity and size smaller than 600 nm were recovered, which has a high potential for the production of hydrofluoric acid. Besides, the precipitation was significantly affected by Ca/F molar ratio, stirring time, temperature, and solution pH. Furthermore, the thermodynamics and kinetics were investigated in detail to reveal the crystallization process. As a result, the defluorination reaction followed the pseudo-second order reaction kinetics model. Also, CO2 in the air adversely influenced the CaF2 purity. Based on this facile method, a high lime utilization efficiency was applied to defluorination, which contributed to protecting the environment and saving costs. This study, therefore, provides a feasible approach for the green recovery of fluorine resources and has significance for related research.

Experimental Study on the Strength and Microstructure of Red Mud-Based Silty Sand Modified with Lime–Fly Ash

This study aimed to assess the viability of utilizing lime–fly ash (LF) and red mud (RM) in the modification of silty soil (LF-RMS) for subgrade filling. The primary objective of this research was to analyze the mechanical characteristics and examine the curing mechanisms associated with said modified materials. Different curing times were utilized in the analysis of mechanical properties (e.g., via unconfined compression testing), microstructure (via scanning electron microscopy, X-ray diffraction, and thermogravimetric-differential thermal analysis), and environmental indices (via assessment of corrosivity, heavy metal concentration, and radioactivity) with various dosages of red mud (DRM) and Lime–fly ash (DLF). Analyses of the curing mechanisms, failure modes, microstructures, and degrees of environmental impact associated with LF-RMS were also undertaken. The tests indicated that the unconfined compressive strength (UCS) exhibited an initial increase followed by a decrease as the DRM and DLF levels increased. Additionally, the strength of LF-RMS increased with an increase in curing time. It is worth noting that the specimen composed of 20% LF and 23% RM (D20%LF+23%RM) demonstrated a maximum UCS value of 4.72 MPa after 90 days of curing, which indicates that it has the strongest ability to resist deformation. The strength of the specimen cured for 90 days was 1.4 times higher than that of the specimen cured for 7 days (1.97 MPa). Furthermore, the toxic concentration and radionuclide index of LF-RMS were significantly reduced compared to those of pure RM. The overall concentration of heavy metals in the D20%LF+23%RM specimen decreased by more than 60% after curing for 28 days. The internal irradiation index and the external irradiation index decreased by 1.63 and 1.69, respectively. The hydration products in LF-RMS play a key role in the solidification of heavy metals, and the alkaline environment provided by RM also contributes to the precipitation and replacement of heavy metals. In this study, red mud, fly ash and lime were used to modify silty soil. The central tenets of sustainable development may be achieved through the reuse of RM as a road filler.

Kinetics of soil re-acidification under no-tillage system

The rate and amount of Al3+ released from re-solubilization of the Al-containing polymers and minerals due to the increase in proton activity in the soil solution in subtropical regions is scarce in the literature. The objective of the present study was to track the Al3+ reappearance following its neutralization during the switch from a conventional tillage system to a no-till (NT) system. For this purpose, we evaluated a long-term lime experiment under NT on a subtropical Ultisol. The treatments included varying lime rates, with different historic of lime reapplication. Soil samples were taken at the 0–5, 5–10, and 10–15 cm depth in 1988, 1994, 1995, 1996, 2001, 2003, 2006, 2012, and 2022. The re-solubilization of Al-containing soil polymers and minerals in the 0–15 cm soil layer proceeds slowly in the first 10 years; afterwards, the rate and amount of Al3+ released increased. However, regardless of the lime treatment, the soil never returns its natural acidic state, even after 34 years of the first liming operation. A decrease in the intensity of reappearance of exchangeable Al3+ in the soil profile is clearly observed, compared to the treatment without reapplication of surface lime. We have observed that it takes 7–9 years for 10% of the effective cation exchange capacity to be occupied by Al3+ if limestone is not reapplied on the soil surface; if underdoses are reapplied this level can be maintained for 13–15 years. Furthermore, if larger and more frequent lime doses are used, a low Al3+ saturation (<10%) can be maintained permanently. These findings emphasize the importance of an appropriate liming process at the start of NT, followed with surface limestone reapplication, to ensure a very low Al3+ saturation over a long period of time in the 0–15 cm soil layer.

Mechanism of improvement and best-fit models for the prediction of geotechnical properties of lime stabilized expansive soil used in pavement subgrade

The performance of a pavement mainly depends on the quality of the subgrade layer. Expansive soils (ES) are extensively found worldwide including Pakistan. The inadequate strength and swelling behaviour of these soils are the main problems in any road construction project. Several researchers in the last decades have attempted to improve expansive soil utilizing various materials such as lime, brick kiln dust and fly ash. The purpose of this research was to evaluate the effect of lime on the engineering properties of the ES of a highway subgrade in the Sialkot region of Pakistan. The influence of different lime dosages (0%, 2%, 4% and 6%) at curing ages (1, 7, 14 and 28 days) has been examined by pH tests, plasticity tests, compaction tests, unconfined compressive strength (UCS), free swell index, and California Bearing Ratios (CBR). A field CBR and plate load test (PLT) on the natural soil and optimum lime-treated soil with various curing periods have been carried out for applicability as subgrade material. The test findings demonstrated that higher lime dosages increased the strength and ultimate bearing capacity (𝑞𝑢𝑙𝑡) of improved ES and at the same time decreased the free swelling index (FSI), optimum moisture content (OMC), maximum dry density (MDD) and permanent deformation of the subgrade soil. The UCS values of soil treated with 2%, 4% and 6% lime increased almost by 324%, 523%, and 249% for unsoaked samples and 285%, 351% and 231% for soaked samples respectively as compared to the plain soil at 28 days curing period. The laboratory CBR values significantly increased 2.35-8.50 times and field CBR improved 5.6 times as compared to the plain soil. The 𝑞𝑢𝑙𝑡 of lime-treated soil increased by 162% as compared to the plain soil and permanent deformation reduced from 33 mm to 2 mm after 28 days. Furthermore, equations were developed to estimate the best fit for the prediction of various geotechnical parameters and coefficient of determination (R2 ) values for all equations were found higher than 0.90. From the results, it has been concluded that adding the optimum lime content of 4% by weight satisfies the requirement for the subgrade construction of highways and the developed expressions can provide a scientific basis for estimating the geotechnical parameters.

Present status of brood stock management and breeding operations at Carp Hatcheries in Jashore, Bangladesh

Sustainable aquaculture production depends on the proper management of brood stock. In this regard, multiple survey studies were reviewed to assess the present status of management of carp brood stock at Jashore region in Bangladesh from March 2023 to August 2023. A total of 38 hatcheries were selected in Jashore. The areas of ponds were ranged from 33.33 to 400 decimal and shape with maximum rectangular. The green color water of pond was 79% and 75% practice pond drying. Most of the farmers applied liming doses were ranged from 500- 1200 gm dec-1. Most of the farmers used rotenone (39%) to control predators in the brood stock pond. Different sorts of fertilizers both organic and inorganic were applied. Most of the brood stocks (39%) were collected from the hatcheries and the rest of them were collected from other pond, World fish, BFRI and the natural sources (Halda and Padma River). Moreover, 4 carp species (rui, catla, mrigala and kalbashu) among 13 endemic and 4 exotic carp species (silver carp, grass carp, bighead and common carp) out of 6 exotic carp’s species were used for seed production. Negative selection of brood stock was performed in few hatcheries in order to reduce the cost for collecting or purchasing good quality broods. The formulated feed which contained 20-30% protein for carp brood stock were prepared using the indigenous ingredients including mainly rice bran, mustard oil cake, vitamin and mineral premix, wheat flour, fish meal and soya bean flour and maize flour. The main problem of hatchling production is Argulosis (fish lice) diseases which causes 95% of hatchlings mortality. Finally, these survey findings indicate that proper brood stock management could be a good approach to attain the main purpose of aquaculture.

BioWin Modeling of CalPrex Phosphorus Recovery from Wastewater Predicts Substantial Nuisance Struvite Reduction

The wastewater treatment industry could benefit from new technologies for the removal and recovery of phosphorus (P). The CalPrex precipitation reactor has the potential to recover P in a readily land-applicable form by treating organic acid digestate with calcium hydroxide to produce brushite. Using data from a pilot-scale reactor at the local Nine Springs Wastewater Treatment Plant in Madison, WI, we modified the plant’s BioWin configuration using BioWin 6.2 to model the CalPrex technology and estimate performance under a variety of conditions. We produced dose/response curves for a range of possible lime dosages to estimate the impact of reagent dosage on the quantity and composition of precipitate produced by the CalPrex reactor and characterize the effects on downstream anaerobic digester performance. CalPrex was found to capture 46% of the plant’s influent P, reducing nuisance struvite precipitates by 57% and biosolid sludge production by 14%. The CalPrex module was also tested in two predesigned plant configurations in the BioWin cabinet with the intention of testing applicability to other configurations and searching for the impacts of CalPrex on treatment train performance. This is the first work simulating a full-scale implementation of CalPrex and the first to model interactions of CalPrex with other treatment processes.

Effect of lime application on phosphorus adsorption and desorption in post-active acid sulfate soil, Thailand

The application of lime is the general method of improving acid sulfate soils. However, if a lot of lime is applied, it can reduce the bioavailability of nutrients in the soil, especially phosphorus. The objective of this study was to investigate the effects of liming at different rates on the availability, adsorption, and desorption of phosphorus in two post-active acid sulfate soils (Ay and Se). The experiment was performed in the laboratory. The experiment was laid out in a completely randomized design (CRD) with four treatments and three replicates, i.e., the application of lime at a rate of 0 (control), 0.5, 1.0, and 2.0 times the lime requirement (LR). The lime requirements of the soils in the Ay and Se were 5,690 and 12,250 kg CaCO3/ha, respectively. The finding revealed that increasing the amount of lime could increase soil pH, available phosphorus, and the phosphorus activation coefficient. Application of lime at a dosage of 1.0-2.0 LR resulted in the highest phosphorus adsorption maximum (Qm) (380 mg/kg), while 0.5 LR resulted in the lowest Qm (353 mg/kg) in Se soil only. As lime dosage increased, phosphorus desorption maximum (Dm) and phosphorus desorption ratio (Dr) increased, with 2.0 LR yielding the highest values (124 mg/kg and 23.6 percent for Ay soil, and 77.3 mg/kg and 20.3 percent for Se soil, respectively). The results suggested that applying lime according to the lime requirement test, especially 2.0 LR, is the best option to promote the release of phosphorus in post-active acid sulfate soils.

Effect of lime (CaOH+) on chalcopyrite-arsenopyrite separation in high gradient magnetic separation: Experiment and molecular simulation

During the flotation of chalcopyrite from arsenopyrite, the addition of lime (with CaOH+ as the active component) can affect the subsequent high-gradient magnetic separation (HGMS) performance. However, this issue has been overlooked in previous researches. The present study confirms this effect and elucidates its underlying mechanism. Findings demonstrate that CaOH+ could decrease the magnetic moment of Fe atoms in chalcopyrite, deteriorating its separation from arsenopyrite via HGMS method. For a high-arsenic copper ore assaying 0.63 % Cu and 0.78 % As with chalcopyrite and arsenopyrite as the dominant copper-bearing and arsenic-bearing minerals, the HGMS results has confirmed that increasing the lime dosage from 0 kg/t to 14 kg/t reduced the copper grade in the copper concentrate from 0.92 % to 0.61 % and decreased the copper recovery from 67.03 % to 53.95 %. However, the arsenic grade and recovery in the concentrate were improved from 0.35 % to 0.64 % and from 28.27 % to 42.19 %, respectively. The calculations using Density Functional Theory and Crystal-Field Theory revealed that the interaction between Fe ions in chalcopyrite and CaOH+ in lime leads to a considerable change in the single electron occupancy of the d orbitals, that is, it transitions from a high-spin state to a low-spin state; thus, the magnetic susceptibility of the chalcopyrite decreases, reducing the HGMS efficiency for separation of chalcopyrite from arsenopyrite. The findings of this study provide considerable theoretical insights and improved understanding for the effect of lime on the chalcopyrite-arsenopyrite separation efficiency in HGMS process.

The Efficiency of Ascaris Spp. Eggs Inactivation in Sewage Sludge by Lime Dosage, Ammonia Concentration, and Temperature Variation

Introduction: Ascaris spp. eggs threaten sludge reuse because they are usually more environmentally resistant than other microorganisms. Consequently, the WHO recommended an acceptable limit of &lt;1 helminth egg per gram of total solid as a health-based target for treated feces and fecal sludge and aimed to ascertain the effectiveness and reduction rate of Ascaris spp. eggs in sludge at various lime doses, ammonia concentrations, and temperature values. Methods: Eggs were detected and enumerated using the flotation and sedimentation principle. The reduction process was performed in batches with quick lime doses of 30% and 50% w/w, ammonia concentrations of 1,000 and 5,000 mg/L, and temperatures of 30°C and 50°C. Results and Discussion: The number of eggs of Ascaris spp. fertile in the ponds was 1.38 ± 1.38 eggs/gram to 42.98 ± 13.09 eggs/gram, and the infertile amount was 0.46 ± 0.80 eggs/gram to 17.82 ± 6.55 eggs/gram. Using a temperature of 40°C, 50% CaO, and 5,000 ppm ammonia resulted in the highest percentage of reduction, 97.98 - 98.09% but 1.12 eggs/gram was remaining. Conclusion: Higher pH and ammonia levels primarily affect egg decrease in Ascaris spp. To reduce 99% of Ascaris spp. eggs until it reaches &lt;1 egg/g, a dose of 50% CaO is required, with 5,000 ppm ammonia at a temperature of 40°C for 2.7 hours.

Kajian Nilai pH Tanah pada Berbagai Toposekuen dan Kelas Lereng yang Berbeda pada Lahan Perkebunan Karet Rakyat di Kecamatan Pelepat Ilir, Kabupaten Bungo, Jambi

Soil pH value either with KCl solution or with H2O are two important indicators needed to describe soil acidity. This study aims to determine the distribution of soil pH values in smallholder rubber plantations with different land topography classes in Pelepat Ilir Subdistrict, Bungo Regency, Jambi Province. The study used a survey method with a toposequence concept approach at a semi-detailed level, where observation points were made based on the upper tread polypedon, middle tread polypedon, and lower tread polypedon at each level of percent slope 15-24%, 8-15%, and 3-8%, and flat tread polypedon at a percent slope of 0-3%. Ten composite soils were taken from a mixture of 3 individual soil samples at each polypedon using a soil drill at a depth of 0-30 cm from the soil surface. Soil pH value analysis was conducted in the laboratory on each composite. The results showed that the pH value of the soil with 1:2 H2O solution was very acidic, and acidic for 1:2.5 KCl solution. The distribution of soil pH values showed that the lower slope had a higher pH value than the middle slope, and the upper slope had the lowest pH. Soil pH values decreased as the slope increased, and soils with flat topography were considered more fertile than those with high slopes. This result can be a recommendation in determining liming and fertilization doses, where higher doses are required for high slope soils than flat soils for optimum agricultural yields.