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Acid mine drainage severely affects metallic materials due to the high acidity and oxidising capacity of these lixiviates. A study was carried out to evaluate the time evolution of the mechanical properties of AISI 1020 carbon steel and AW6060 aluminium in contact with acid mine drainage. Weight loss, fatigue and tensile strength were evaluated in two different scenarios, one involving erosion corrosion (dynamic scenario) and the other involving chemical corrosion only (static scenario). Over 80 days of exposure in a static scenario, weight loss is almost 2% for aluminium and 0.5% for steel, fatigue strength is reduced by 28% for steel and ultimate tensile strength is reduced by almost 5% for aluminium and by 2.5% for steel. In a dynamic scenario, the weight loss after 4 days of exposure is 30–35% for both materials, the fatigue strength is reduced by almost 50% for steel, the ultimate tensile strength is reduced by 33% for aluminium and by almost 5% for steel. Acid drainage causes an increase in brittleness and a decrease in stiffness of these materials, much more rapidly in a dynamic environment favoured by the effects of erosion corrosion.

Mitigating acid mine drainage (AMD) at its source, specifically within rocks containing pyrite in underwater environments, poses a significant environmental challenge worldwide. Existing passivation techniques are primarily designed for open-air conditions, involving direct contact with coating materials at a solid–liquid interface, making them ineffective beneath a water barrier. In this study, we introduce a novel passivation method inspired by the design of underwater bio-adhesives. Tannic acid (TA) combined with polyethylene glycol (PEG) was employed to form a hydrophobic film directly on the pyrite surface, overcoming water resistance and addressing the limitations of current techniques. Electrochemical experiments and chemical leaching experiments were conducted to evaluate the oxidation resistance of the passivating films. TA–PEG-coated pyrite exhibited a lower oxidation rate and a higher static contact angle of 126.2°, achieving suppression efficiencies of 71.6% for total Fe release and 68.1% for total S release. A comprehensive characterization approach, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), was employed to investigate the passivation mechanism. The results of this study may provide new insights into the preparation of simpler and greener passivating agents to suppress pyrite oxidation at its source in underwater environments. [ABSTRACT FROM AUTHOR]

The Lorraine mine site in Témiscamingue region (Québec, Canada) was reclaimed with a cover with capillary barrier effects (CCBE) to limit acid mine drainage generation. The main objective of this study is to predict the long-term hydrogeological behaviour of the CCBE at Lorraine site, including the influence of vegetation and climate change (CC). Numerical simulations showed that performance of the CCBE is: (1) not affected by forest vegetation and CC in the saturated zone in the north of the Lorraine site and (2) more sensitive to vegetation in the unsaturated zone in the south where the phreatic level is low. [ABSTRACT FROM AUTHOR]

Bioremediation of acid mine drainage (AMD) was often challenged by poor tolerance of sulfate-reducing bacteria (SRB) to heavy metals and low bioactivity. The highly active immobilized particles with Fe0/Fe2+ enhanced SRB (Fe0/2+-SRB) were prepared by the microorganism immobilization technique. Three dynamic columns were constructed to investigate the adsorption capacity of Fe0/2+-SRB for Mn2+ under varying adsorption layer heights, inflow velocity, and initial Mn2+ concentrations. The role of each matrix material in the immobilized particles was explored, the mechanism of AMD remediation by Fe0/2+-SRB was revealed, and the adaptability of Fe0/2+-SRB to AMD under various initial conditions was investigated. The results showed that the prepared Fe0/2+-SRB exhibited a well-developed surface pore structure. When the adsorption layer height was 200 mm, the influent flow rate was 5 × 10−5 m3/s, and the initial manganese ion concentration was 10 mg/L, the maximum dynamic adsorption capacities (qe) of Mn2+ for each dynamic column were 7.8430, 4.7627, and 8.7677 mg/g, respectively. Compared to dynamic columns 1# and 2#, dynamic column 3# showed the best performance in treating AMD, and the Thomas model effectively described the adsorption kinetics of Mn2+ by Fe0/2+-SRB(3#). Microstructural analysis indicated that chemical adsorption, ion exchange, dissimilation–reduction reaction, and surface complexation occurred between the various matrix materials in Fe0/2+-SRB(3#). Mn2+ was primarily removed in the form of metal sulfide (MnS), and Fe0/Fe2+ could promote the dissimilatory reduction of SO42− by SRB to form S2−. Fe0/2+-SRB(3#) was able to adapt to AMD with initial conditions of pH was 2~4, SO42− < 2500 mg/L, and Mn2+ < 20 mg/L. The research results provide new insights into the remediation of AMD, using a combined microbial-adsorption technology. [ABSTRACT FROM AUTHOR]

Abstract Acid mine drainage (AMD), characterized by its acidity and high content of heavy metals, is a significant global environmental problem that harms human health through its impact on rivers. Therefore, this study aims to identify heavy metals in both surface and underground AMD-polluted karst rivers, focusing on the Zhijin River area which is severely affected by AMD, and assess their health risks to residents. Through the collection of 30 surface water samples and 16 groundwater samples from both wet and dry seasons, the study examines the concentration, sources of pollution, and health implications of six heavy metals (Fe, Mn, Cr, Cd, As, and Hg). The results showed that Fe and Mn levels in surface water were highly polluted during both seasons, especially during the wet season, with Fe levels reaching 20.0 mg/L and Mn levels reaching 1.9 mg/L. Further correlation and principal component analyses revealed that mining activities are the primary contributors to the contamination in this region. Health risk assessments and Monte Carlo simulation, including both deterministic and probabilistic, showed that the noncarcinogenic health risk indices for surface water and groundwater were within acceptable limits for both seasons. However, groundwater poses a higher carcinogenic risk to children, with As levels during the wet season and Cr levels during the dry season warranting close monitoring. Factors such as body weight and intake rate played a crucial role in health risk evaluations. This study underscores the need for further attention to groundwater risk, temporal heterogeneity in the Zhijin River.

Abstract Heavy metal pollution is a global environmental issue, and microorganisms play a crucial role in the bioremediation of heavy metal-contaminated wastewater. The study isolated heavy metal-resistant bacterium and observed their absorption ability toward Pb2+, Cd2+ and Zn2+. We isolated Agrobacterium tumefaciens S12 from acid mine drainage. The various factors influencing its adsorption performance, including pH, biomass dosage, initial metal ion concentration, and adsorption temperature, were investigated in detail. Chemisorption controls the adsorption rate due to the results better fitted by pseudo-second order kinetics. The maximum adsorption capacities of Pb2+, Cd2+ and Zn2+ on A. tumefaciens S12 were 234, 58 and 51 mg g−1 at 30 °C from Langmuir isotherm, respectively. The adsorption processes for the three heavy metal ions were spontaneous and exothermic in nature. In bimetallic systems, biosorption of Pb2+ ions was preferential to that of Cd2+ and Zn2+. Furthermore, scanning electron microscopy coupled to energy dispersive spectroscopy, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy analysis demonstrated that the adsorption mechanisms include ion-exchange, complexation interaction between the heavy metal ions and the functional groups on the surface of biomass. The obtained results indicated that A. tumefaciens S12 can be applied as an efficient biosorbent in bioremediation technology to sequestrate heavy metal ions from aqueous solution.

The increasing mining activities have led to the problem of acid mine drainage (AMD) pollution. A method that combines biochar treatment as an adsorbent with wetland sediment treatment as a source of sulfate-reducing bacteria is used to address AMD effectively. This research aimed to determine the ability of biochar in combination with wetland sediment treatment to reduce sulfate and heavy metal content in acid mine drainage wastewater. This research was conducted on a laboratory scale in an AMD wastewater treatment reactor with the following treatments of biochar mixed with wetland sediment. Observations included sulfate content, pH, and heavy metal content. Scanning electron microscope (SEM) analysis was also performed on the biochar. SEM observations revealed the presence of small, dense, and irregularly shaped pores on the surface of the biochar. The results on day 30 showed that biochar mixed with wetland sediment was able to reduce sulfate concentration by 74.19% and reduced Pb by 73.79%, compared with treatment sediment only to 64.81% sulfate concentration and reduced Pb by 53.85%, treatment biochar only had reduced sulfate of 46.90% and reduced Pb by 58.67% and control 1.79% sulfate concentration and reduced Pb by 1.87%.

The mining industry generates acid mine drainage (AMD) characterized with a low pH value and high dissolved metal concentration that leads to the negative impacts on the environment and human health. The objectives of this research were to investigate the growth response of mixed culture of microalgae Chlorella sorokiniana and Monoraphidium neglectum in a liquid media contaminated with AMD; generate the optimum environmental conditions (pH value and contact time) to determine the efficiency biosorption of iron and manganese contained in the solution of AMD into the consortium of microalgae; and quantify the maximum removal amount of iron and manganese contained in the solution of AMD by utilizing microalgae consortium of Chlorella sorokiniana and Monoraphidium neglectum as biosorbent. AMD used in this research was characterized with a pH value of 1.65 with iron and manganese concentrations of 8.28 mg/L and 4.57 mg/L. The research of biosorption was conducted in 150 rpm with pH level variations of 4, 5, and 6, and contact time variations of 60, 120, and 180 min. The maximum value of iron and manganese removals occurred when pH level reached 5 at 180 min of contact time with removal efficiency of 89.73% for iron and 94.53% for manganese. The results proved that the mixed culture of microalgae namely Chlorella sorokiniana and Monoraphidium neglectum can be utilized to remove iron and manganese contained in acid mine drainage. [ABSTRACT FROM AUTHOR]

An in-process technology approach is proposed to identify the source of acid mine drainage (AMD) generation and prevent its formation in a porphyry copper waste rock (WR). Adopting actions before stockpiling the WR enables the establishment of potential contaminants and predicts the more convenient method for AMD prevention. A WR sample was separated into size fractions, and the WR’s net acid-generating potential was quantified using chemical and mineralogical characterization. The diameter of physical locking of sulfides (DPLS) was determined, and the fractions below the DPLS were desulfurized using flotation. Finally, the WR fractions and tailing from the flotation test were submitted to acid-base accounting and weathering tests to evaluate their acid-generating potential. Results show that the WR’s main sulfide mineral is pyrite, and the DPLS was defined as 850 µm. A sulfide recovery of 91% was achieved using a combination of HydroFloat® and Denver cells for a size fraction lower than DPLS. No grinding was conducted. The results show that size fractions greater than DPLS and the desulfurized WR are unlikely to produce AMD. The outcomes show that in-processing technology can be a more proactive approach and an effective tool for avoiding AMD in a porphyry copper WR.

Abstract Acid mine drainage (AMD) is a mining-associated environmental problem that mainly pollutes water resources worldwide, making it imperative to find sustainable remediation solutions. To find effective treatment solutions for AMD, it will be beneficial to understand how this area of research has evolved over the years. Thus, this work provides a bibliometric analysis and narrative review of previous research articles that have focused on AMD treatment and management over the past 47 years and highlights the associated challenges and how to overcome them. Research articles addressing the treatment and management of AMD were retrieved from the Scopus database, using specific search criteria. The Scopus Analyze Tool and VOSviewer were used to analyze the publications to provide information on the publication distribution, countries of publication, authorship, keywords, field of study, and author affiliations, while the narrative review provides an overview of how AMD treatment technologies have evolved over these years. The top ten most published countries are developed countries except for South Africa (ranking number 4). This review revealed that several approaches have been developed for AMD treatment and management. It was observed that AMD treatment methods have not drastically changed over the years. Instead, earlier treatment techniques are being improved to develop new and more effective ones. The most recent remediation approach involves the valorization of AMD for the recovery of new materials in economically viable amounts. This is a sustainable approach to AMD treatment; however, it comes with challenges that can be overcome through more research in this area.

Acid mine drainage (AMD) is an environmental concern, and its discharge into the surrounding environment can lead to acidification of water bodies and soil. In this research, red mud (RM) with alkaline pH as aluminum industry waste was implemented as an adsorbent for sulfate removal, which can be available in AMD and adsorption processes as an influential method was applied for AMD treating. Seawater washing (BRM), acid treatment (HRM), and composition with chitosan (CRM) were employed as RM modification methods. Various analytical methods were applied, including x-ray fluorescence spectroscopy (XRF), Fourier-transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET), inductively coupled plasma analysis, and zeta potential, to have a clear comprehension of the sulfate adsorption behaviors and performance of activated methods. These methods have had desirable effects on the sulfate adsorption and adsorption amount, which range from 1.1 mg g−1 for RM reached to 13.4, 39.7, and 67.4 mg g−1 for BRM, HRM, and CRM, respectively. XRF results demonstrated a decrease in calcium and sodium ion amounts that can occur due to their dissolution in the acidic solution. It can create the active surface areas for adsorption onto RM with acid washing. Based on FTIR results, sharp intensity vibration was observed in BRM, HRM, and CRM after sulfate adsorption in the 1,100 cm−1 band that is approximately related to SO42− vibration. BRM porosity decreased from 0.0686 to 0.0345 cm3 g−1 due to various salts' precipitation in seawater, but the porosity volume and specific surface area increased for HRM from 0.0686 to 0.184 cm3 g−1 due to dissolution of ions in HCl. In addition, zeta potential increased to positive amounts from 2.7 to 3.4, 3.8, and 4.5 mv for BRM, HRM, and CRM, respectively. Langmuir isotherm indicated that the highest adsorption amount (qm) as a calculated parameter for BRM, HRM, and CRM was 0.88, 2.45, and 18.6 mg g−1 , respectively. Among modification methods, combination RM and chitosan had the highest impact and increases sulfate removal and adsorption amount at lower pH levels due to further positive charge on the CRM surface. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is one of the main environmental problems associated with mining activity, whether the mine is operational or abandoned. In this work, several precipitates from this mine drainage generated by the oxidation of sulfide minerals, when exposed to weathering, were used as adsorbents. Such AMD precipitates from abandoned Portuguese mines (AGO, AGO-1, CF, and V9) were compared with two raw materials from Morocco (ClayMA and pyrophyllite) in terms of their efficiency in wastewater treatment. Different analytical techniques, such as XRD diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N2 adsorption isotherms, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) were used to characterize these natural materials. The adsorption properties were studied by optimizing different experimental factors, such as type of adsorbent, adsorbent mass, and dye concentration by the Box–Behnken Design model, using methylene blue (MB) and crystal violet (CV) compounds as organic pollutants. The obtained kinetic data were examined using the pseudo-first and pseudo-second order equations, and the equilibrium adsorption data were studied using the Freundlich and Langmuir models. The adsorption behavior of the different adsorbents was perfectly fitted by the pseudo-second order kinetic model and the Langmuir isotherm. The most efficient adsorbent for both dyes was AGO-1 due to the presence of the cellulose molecules, with qm equal to 40.5 and 16.0 mg/g for CV and MB, respectively. This study confirms the possibility of employing AMD precipitates to adsorb organic pollutants in water, providing valuable information for developing future affordable solutions to reduce the wastes associated with mining activity. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is an environmental issue linked with mining activities, causing the release of toxic water from mining areas. Polyethersulphone (PES) membranes are explored for AMD treatment, but their limited hydrophilicity hinders their performance. Chitosan enhances hydrophilicity, addressing this issue. However, the effectiveness depends on chitosan's degree of deacetylation (DD), determined during the deacetylation process for chitosan production. This study optimized the chitin deacetylation temperature, alkaline (NaOH) concentration, and reaction time, yielding the highest chitosan degree of deacetylation (DD) for PES/chitosan membrane applications. Prior research has shown that high DD chitosan enhances membrane antifouling and hydrophilicity, increasing contaminant rejection and permeate flux. Evaluation of the best deacetylation conditions in terms of temperature (80, 100, 120 °C), NaOH concentration (20, 40, 60 wt.%), and time (2, 4, 6 h) was performed. The highest chitosan DD obtained was 87.11% at 80 °C, 40 wt. %NaOH at 4 h of chitin deacetylation. The PES/0.75 chitosan membrane (87.11%DD) showed an increase in surface hydrophilicity (63.62° contact angle) as compared to the pristine PES membrane (72.83° contact angle). This was an indicated improvement in membrane performance. Thus, presumably leading to high contaminant rejection and permeate flux in the AMD treatment context, postulate to literature. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) prevention or remediation is a major issue of the environmental management of sulfide-bearing active and abandoned mining sites, the main sources of acidic waters being wastes and tailings. The present work intends to check a circular economy approach to such issues in the mining region of Sardinia, where environmental pollution, due to AMD, is a major concern. Tests were conducted on basic drainage-producing feldspar mining wastes that could be recycled as buffering agents of sulfide-bearing tailings. Among the sulfide-bearing abandoned mining sites investigated, Furtei epithermal gold deposit tailings are the most polluting and those that can better test the buffering agent efficacy. Buffering test results show that buffering to near-neutral conditions can be attained following steps similar to those of pure calcite buffer. The buffering potential of the recycled waste is due to both the buffer calcite content, which provides short-term buffering, enhanced by feldspar content that can provide long-term buffering. Buffered waters show a dramatic decrease in the concentration of most of the metals present in the leachate, down to conditions that meet the requirements for the discharge of industrial waters according to Italian legislation. [ABSTRACT FROM AUTHOR]

Abstract Aiming at the acid mine drainage (AMD) in zinc, copper and other heavy metals treatment difficulties, severe pollution of soil and water environment and other problems. Through the ultrasonic precipitation method, this study prepared fly ash-loaded nano-FeS composites (nFeS-F). The effects of nFeS-F dosage, pH, stirring rate, reaction time and initial concentration of the solution on the adsorption of Zn(II) and Cu(II) were investigated. The data were fitted by Lagergren first and second-order kinetic equations, Internal diffusion equation, Langmuir and Freundlich isotherm models, and combined with SEM, TEM, FTIR, TGA, and XPS assays to reveal the mechanism of nFeS-F adsorption of Zn(II) and Cu(II). The results demonstrated that: The removal of Zn(II) and Cu(II) by nFeS-F could reach 83.36% and 70.40%, respectively (The dosage was 8 g/L, pH was 4, time was 150 min, and concentration was 100 mg/L). The adsorption process, mainly chemical adsorption, conforms to the Lagergren second-order kinetic equation (R2 = 0.9952 and 0.9932). The adsorption isotherms have a higher fitting degree with the Langmuir model (R2 = 0.9964 and 0.9966), and the adsorption is a monolayer adsorption process. This study can provide a reference for treating heavy metals in acid mine drainage and resource utilization of fly ash.

In China, the sulfate levels in acid mine drainage (AMD) are generally high. Developing an effective method to eliminate sulfate from wastewater is imperative for AMD treatment. Considering the promising prospect of treating AMD with converter steel slag, we analyze the removal effect and mechanism of sulfate in AMD treatment with steel slag by a single-factor experimental method. The adsorption amount and removal rate are determined using an ultraviolet spectrophotometer. The findings reveal that the removal efficiency of sulfate was influenced by the particle size of steel slag, pH of wastewater, solid–liquid ratio, and sulfate concentration. When the particle size of steel slag is less than 75 μm, the pH of the system is 2, the solid–liquid ratio is 70 g·L−1, and the initial sulfate concentration is 2000 mg·L−1; moreover, the removal rate of sulfate is the highest, which is 79.15% and the adsorption capacity is 36.79 mg·g−1. By linearly fitting the adsorption capacity data to the Langmuir and Freundlich equations, the adsorption process of sulfate on the steel slag surface is more in line with the Freundlich adsorption model. Furthermore, thermodynamic calculations demonstrate that the Gibbs free energy change (∆G) of adsorption is negative and enthalpy change (∆H) and entropy change (∆S) are both positive, which demonstrates that the process of sulfate adsorption on steel slag is spontaneous, entropy-driven, and endothermic chemical adsorption. Moreover, when the adsorption temperature is between 301 and 321 K, the adsorption capacity increases with increasing adsorption time and temperature, and when the adsorption time reaches 1320 min, the increasing trend of adsorption capacity slows down. Kinetic calculation results indicate that the equilibrium adsorption amount calculated using the secondary reaction rate equation is similar to the experimental equilibrium adsorption capacity, suggesting that the adsorption of sulfate on the steel slag surface conforms to the secondary adsorption kinetic model. Sulfate removal is mainly controlled by chemical processes, and material transport is not the main controlling step. Based on the intraparticle diffusion fitting results, the adsorption process goes through three stages: external rapid adsorption, internal gradual diffusion, and finally equilibrium. X-ray diffraction of steel slag before and after adsorption exhibits that sulfate existed on the steel slag surface in the form of gypsum, which was corroborated by Fourier-transform infrared spectroscopy analysis and scanning electron microscopy characterization. In conclusion, the reaction between steel slag and sulfate is dominated by multilayer chemical adsorption combined with chemical precipitation, electrostatic adsorption, and surface complexation.

Abstract A new idea to alleviate environmental pollution is the development of low-cost adsorbents using natural minerals and fishery wastes to treat high concentrations of heavy metal pollutants in acid mine drainage (AMD). Adsorbent morphology, adsorptive and regenerative capacity, and application potential are limiting factors for their large-scale use. Oyster shells capable of releasing alkalinity were loaded on the surface of lignite to develop two composite adsorbents with different morphologies (powdery and globular) for the treatment of AMD containing Pb(II) and Cd(II). The results show that the ability of the adsorbent to treat AMD is closely related to its morphologies. The pseudo-second-order kinetic model and the Langmuir model are suitable to describe the adsorption process of OS-M(P), and the maximum adsorption saturation capacities of Pb(II) and Cd(II) are 332.6219 mg/g and 318.9854 mg/g, respectively. The pseudo-second-order kinetic model and the Freundlich model are suitable to describe the adsorption process of OS-M(G). A synergistic result of electrostatic adsorption, neutralization precipitation, ion exchange and complex reaction is achieved in the removal of Pb(II) and Cd(II) by two morphologies of adsorbents. The regeneration times (5 times) and recovery rate (75.75%) of OS-M(G) are higher than those of OS-M(P) (3 times) and recovery rate (20%). The ability of OS-M(G) to treat actual AMD wastewater is still better than that of OS-M(P). OS-M(G) can be used as a promising environmentally friendly adsorbent for the long-term remediation of AMD. This study provides a comprehensive picture of resource management and reuse opportunities for natural mineral and fishery wastes.

Acid Mine Drainage (AMD) contains Fe(II) and Mn(II) metals, which can cause environmental pollution. This research aimed to investigate the potency of activated carbon made from coal as an adsorbent in AMD treatment. The carbon was made of coal and activated with H3PO4 in a weight ratio of 40%, 800 °C for 120 minutes while supplying 1.5 L/min of nitrogen during the carbonization process. The result shows that BET surface area, total pore volume, and iodine number were 296.4 m2/g, 0.156 cc/g, and 1205 mg/g, respectively. The surface contained many fractures, channels, and big holes, as evidenced by the FT-IR and SEM investigations, and it also had acidic surface functional groups. The optimum contact time adsorption for AMD treatment was 30 minutes, and the first concentration of Fe(II) and Mn(II) metals affected the adsorption. The optimum removal of Fe(II) in AMD treatment was 95.27% at an initial concentration of 3.51 ppm, while the optimum removal of Mn(II) was 99.82% at an initial concentration of 5.71 ppm. This activated carbon has a considerable potency to be used as the adsorbent in AMD treatment to reduce Fe(II) and Mn(II) levels.

Acid Mine Drainage (AMD) is a major environmental problem due to low pH, high sulphate content, and dissolved metals. The aim of this study was to investigate the potential of limestone materials for the primary treatment of AMD water. Different doses of limestone were used in this study in the ratio of 0 g/1,000 mL as control, 20 g/1,000 mL, 40 g/1,000 mL, 60 g/1,000 mL, 80 g/1,000 mL, 100 g/1,000 mL, 200 g/100 mL (limestone/AMD) in a batch experiment of 1,500 mL plastic container. The results showed that the pH of AMD water improved to 8.6 at a dose of 100 g/1,000 mL, and the sulphate concentration decreased from 2,277 mg/L to 506 mg/L at a dose of 200 g/1,000 mL. The removal of Fe, Cu, Zn, Mn, and Ni at 200 g/1,000 mL was 99%, 92%, 68%, 96%, and 99%, respectively. The results of this study also showed that the Mn content decreased slowly as the limestone dosage increased. In addition, this study showed that limestone is a good neutralizing agent for increasing the pH of AMD water and reducing sulphate and dissolved metal concentrations. The results of this study indicated that limestone is suitable as a primary treatment agent for AMD water treatment in gold mines in Tanzania.

Sulphate ions removal from Acid mine drainage (AMD) is crucial to mitigate its adverse impact on aquatic and terrestrial ecosystem. Similarly, surplus and unused quantity of the Fly ash, waste from coal-based power plants is also challenging problem. In the present study, Fly ash based low-cost adsorbents (NaOH at 100 oC and HCL at 400 oC) activated Fly ash were synthesized using thermal activation methods. The composition and surface morphology studies were conducted using FTIR, XRD, XRF and SEM-EDX analysis. The Synthesized adsorbents were used to removal of sulphatic ion under various experimental conditions such as initial concentration (5 to 50 mg L−1), contact time (0 to 180 minutes), dose (5 to 40 mg L−1), solution pH (4.5, 5 and 5.5 pH). The optimum removal was 63 ± 1.4 % and 65 ± 1.6 % at room temperature 27 °C, pH 5.5 and 0.6 g L−1 dose of FAZ-HCl and FAZ-NaOH adsorbents respectively. The kinetics models and adsorption isotherm were determined to be pseudo second order (R2 > 0.9919) for FAZ-HCl and pseudo first order which (R2 > 0.9857) was validated and fitted by Freundlich isotherm (R2 > 0.9806 and 0.9932) for FAZ-HCl and FAZ-NaOH. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the catalytic effect of acid mine drainage (AMD) treated sludge based catalyst on the co-pyrolysis of spent coffee grounds and HDPE. The sludge was generated during the treatment of AMD using eggshell and hydrogen peroxide. Theromogravimetric analysis of pyrolysis of spent coffee grounds (SC), HDPE (High density polyethylene), blend of spent coffee grounds and HDPE (SC+HDPE) in the ratio of 1:1, and blended feedstock with sludge derived catalyst (SC+HDPE_AMDC) (1:1 wt. ratio) was conducted at various heating rates of 10 °C/min, 20 °C/min, 30 °C/min and 40 °C/min respectively. Iso-conversional models such as Ozawa Flynn Wall (OFW), Kissinger Akahira Sunose (KAS), Friedman, and Starink were utilized for the determination of activation energy (Ea) of the process. The results showed that using AMD treated sludge based catalyst to the pyrolysis process, enhances its overall efficacy by lowering the activation energy (Ea) (OFW- Ea: 209.11 to 177.14 KJ/mol, KAS-Ea: 208.30 to 173.06 KJ/mol, Friedman- Ea:210.54 to 176.28 KJ/mol, and Starink- Ea:208.60 to 173.44 KJ/mol). Criado's z-master plot (CZMP) method was utilized to analyze the mechanism of the reaction. The pre-exponential factor and thermodynamic parameters were also evaluated. It is concluded that the incorporation of sludge based catalyst (AMDC) lowered enthalpy and randomness of system. Catalytic co-pyrolysis requires less energy, making it more environmental friendly choice for the sustainable processing of biomass and plastics. The present investigation will aid in the design, optimization and scalability.