Iron phosphate-based coating and iron silicate-based coating were used to inhibit the oxidation of sulfide minerals in rainy and submerged environments. The inhibiting effectiveness of coating agents on the oxidation of iron sulfide minerals was investigated using pyrite and rock samples resulting from acid drainage. The film formed with both surface-coating agents was identified by pyrite surface analysis. It was also confirmed that the formation of coatings varies depending on the crystallographic orientation. The inhibitory effects under rainy and submerged conditions were investigated using column experiments. Submerged conditions accelerated deterioration compared to that under rainy conditions. Iron phosphate coating had a significantly better oxidation-inhibitory effect (84.86–98.70

Nano Fe(III) oxide (FO) was used as an amendment material in CO2-assisted pyrolysis of spent coffee grounds (SCG) and its impacts on the syngas (H2 & CO) generation and biochar adsorptive properties were investigated. Amendment of FO led to 153 and 682% increase of H2 and CO in pyrolytic process of SCG, respectively, which is deemed to arise from enhanced thermal cracking of hydrocarbons and oxygen transfer reaction mediated by FO. Incorporation of FO successfully created porous structure in the produced biochar. The adsorption tests revealed that the biochar exhibited bi-functional capability to remove both positively charged Cd(II) and Ni(II), and negatively charged Sb(V). The adsorption of Cd(II) and Ni(II) was hardly deteriorated in the multiple adsorption cycles, and the adsorption of Sb(V) was further enhanced through formation of surface ternary complexes. The overall results demonstrated nano Fe(III) oxide is a promising amendment material in CO2-assisted pyrolysis of lignocellulosic biomass for enhancing syngas generation and producing functional biochar.

Scale is widely observed in the hydrated lime mine drainage treatment plant of the Daedeok Mine in South Korea. In order to understand the environment in terms of the formation of scale minerals, scale and water were collected from the AMD treatment facility and analyzed. In addition, the saturation index was calculated based on geochemical modeling to predict the minerals that could be produced in the AMD treatment facility, and the results were then compared with an analysis of onsite scale minerals. Furthermore, the onsite mine drainage was neutralized from pH 3 to pH 9 in the laboratory, and the precipitates produced were identified. The changes in the Ca2+ and SO42− concentrations were also identified over time for each pH. The results of geochemical modeling predicted the possible precipitation of gypsum, anhydrite, and bassanite after AMD neutralization. Scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) analysis results showed that the main mineral in scale formed at the AMD treatment facility was gypsum, produced by the reaction of SO42− and Ca2+ from lime during AMD. The laboratory neutralization experiment showed that gypsum was produced in all neutralization ranges from pH 3 to pH 9, and the higher the neutralization pH, the greater the amount of gypsum produced. It was demonstrated that simulated amounts of 2 g/L and 7 g/L gypsum at pH 5 and 9 were well matched with the experimental results. Iron (Fe), a major pollutant in the mine drainage system, was rapidly precipitated in the form of iron hydroxides after neutralization. As gypsum is produced slowly and continuously for a long period of time, it results in the growth of scale throughout the flow path. As a method of minimizing gypsum production in the AMD treatment facility using hydrated lime, it is recommended that the facility should be operated at the lowest pH possible, which will also enable the removal of major pollutants, such as iron and aluminum.

This study explored the effects of blending nano iron (III) oxides (NIO) with coffee grounds (CG) in a pyrolytic process under a CO 2 environment on the generation of syngas (H 2 and CO) and biochar properties regarding the removal of Cr(VI) from aqueous solutions. CG and NIO were physically mixed; CG was mass maintained at 1 g while NIO was added. Based on the mass ratio, the resulting solution was named NICG1(NIO/CG ratio=1:1). Compared with the generation amounts of syngas (0.37 mole% H 2 & 0.28 mole% CO) at 650°C from single pyrolysis of CG, co-pyrolysis with NIO-based additives resulted in increased production of syngas, with the measured concentrations of H 2 and CO reaching 0.99 mole% and 0.86 mole% at the same temperature, respectively. During the pH effect experiments, NICG1 demonstrated the highest removal efficiency under acidic conditions with pH = 2. Adsorption kinetic experiments demonstrated that the pseudo-second-order rate model was suitable for assessing the removal of Cr(VI) by NICG1. Furthermore, the removal of Cr(VI) using NICG1 fitted well with the Freundlich isothernm adsorption model (R 2 = 0.9807). In conclusion, co-pyrolysis of blending nano iron(III) oxide and coffee grounds can be considered an efficient resource for simultaneously producing syngas (H 2 and CO) as a fuel (energy resource) and metal-biochar as an adsorbent.

The inhibiting effectiveness of silicate- and phosphate-based surface-coating agents (Na 2 SiO 3 and KH 2 PO 4 ) to the oxidation of iron sulfide minerals was investigated using pyrite and rock samples containing iron sulfide minerals. The film formed with both surface-coating agents was identified by surface analysis. The oxidation of pyrite surface, layered with iron-silicate or -phosphate, was inhibited (77 and 23%, respectively) under accelerated oxidizing conditions with H 2 O 2 , as measured based on the SO 4 2− concentration in the leachate. Oxidation of coated rock samples with iron-silicate or -phosphate was reduced by up to 54 and 33%, respectively. The inhibitory effects under rainy and submerged conditions were investigated using column experiments. Submerged conditions accelerated deterioration compared to that under rainy conditions. KH 2 PO 4 had a significantly better oxidation-inhibitory effect than Na 2 SiO 3 , and at a concentration of 0.3 M, H + elution was inhibited by more than 90% throughout the experiment. Methods for effective film formation was investigated in terms of producing Fe 3+ ; (1) application of coating agents mixed with oxidant (H 2 O 2 ), (2) application of coating agent after the use of the oxidant. The use of a surface-coating agent after applying an oxidant did not inhibit oxidation. The surface coating agent and the oxidizing agent should be applied as a mixture to form a film.

In this study, an adsorbent prepared by natural drying of iron hydroxide-based sludge collected from settling basin at a mine drainage treatment facility located in Gangneung, Gangwon-do was used to remove fluoride in an artificial fluoride solution and mine drainage, and the adsorption characteristics of the adsorbent were investigated. As a result of analyzing the chemical composition, mineralogical properties, and specific surface area of the adsorbent used in the experiment, iron oxide (Fe2O3) occupies 79.2 wt.% as the main constituent, and a peak related to calcite (CaCO3) in the crystal structure analysis was analyzed. It was also identified that an irregular surface and a specific surface area of 216.78 m(2).g(-1). In the indoor batch-type experiment, the effect of changes in reaction time, pH, initial fluoride concentration and temperature on the change in adsorption amount was analyzed. The adsorption of fluoride showed an adsorption amount of 3.85 mg.g(-1) 16 hours after the start of the reaction, and the increase rate of the adsorption amount gradually decreased. Also, as the pH increased, the amount of fluoride adsorption decreased, and in particular, the amount of fluoride adsorption decreased rapidly around pH 5.5, the point of zero charge at which the surface charge of the adsorbent changes. Meanwhile, the results of the isotherm adsorption experiment were applied to the Langmuir and Freundlich isotherm adsorption models to infer the fluoride adsorption mechanism of the used adsorbent. To understand the thermodynamic properties of the adsorbent using the Van't Hoff equation, thermodynamic constants Delta H-o and Delta G(o) were calculated using the adsorption amount information obtained by increasing the temperature from 25 degrees C to 65 degrees C to determine the adsorption characteristics of the adsorbent. Finally, the adsorbent was applied to the mine drainage having a fluoride concentration of about 12.8 mg.L-1, and the fluoride removal rate was about 50%.

Since the mine reclamation scheme was implemented from 2007 in Korea, various remediation programs have been decontaminated the pollution associated with mining and 254 mines were managed to reclamation from 2011 to 2015. However, as the total amount of contaminated mine drainage has been increased due to the discovery of potential hazards and contaminated zone, more efficient and economical treatment technology is required. Therefore, in this study, the adsorption properties of arsenic was evaluated according to the adsorbents which were derived from water treatment sludge(Alum based adsorbent, ABA-500) and granular ferric hydroxide(GFH), already commercialized. The alum sludge and GFH adsorbents consisted of aluminum, silica materials and amorphous iron hydroxide, respectively. The point of zero charge of ABA-500 and GFH were 5.27 and 6.72, respectively. The result of the analysis of BET revealed that the specific surface area of GFH(257 m(2).g(-1)) was larger than ABA-500(126 similar to 136 m(2).g(-1)) and all the adsorbents were mesoporous materials inferred from N-2 adsorption-desorption isotherm. The adsorption capacity of adsorbents was compared with the batch experiments that were performed at different reaction times, pH, temperature and initial concentrations of arsenic. As a result of kinetic study, it was confirmed that arsenic was adsorbed rapidly in the order of GFH, ABA-500(granule) and ABA-500(3mm). The adsorption kinetics were fitted to the pseudo-second-order kinetic model for all three adsorbents. The amount of adsorbed arsenic was increased with low pH and high temperature regardless of adsorbents. When the adsorbents reacted at different initial concentrations of arsenic in an hour, ABA-500(granule) and GFH could remove the arsenic below the standard of drinking water if the concentration was below 0.2 mg.g(-1) and 1 mg.g(-1) , respectively. The results suggested that the ABA-500(granule), a low-cost adsorbent, had the potential to field application at low contaminated mine drainage.

An Alum-sludge based adsorbent (ASBA) was synthesized by the hydrothermal treatment of alum sludge obtained from settling basin in water treatment plant. ASBA was applied to remove fluoride and arsenic in artificially-contaminated aqueous solutions and mine drainage. The mineralogical crystal structure, composition, and specific surface area of ASBA were identified. The result revealed that ASBA has irregular pores and a specific surface area of 87.25 m(2) g(-1) on its surface, which is advantageous for quick and facile adsorption. The main mineral components of the adsorbent were found to be quartz(SiO2), montmorillonite((Al,Mg)(2)Si4O10(OH)(2) 4H(2)O) and albite(NaAlSi3O8). The effects of pH, reaction time, initial concentration, and temperature on removal of fluoride and arsenic were examined. The results of the experiments showed that, the adsorbed amount of fluoride and arsenic gradually decreased with increasing pH. Based on the results of kinetic and isotherm experiments, the maximum adsorption capacity of fluoride and arsenic were 7.6 and 5.6 mg g(-1), respectively. Developed models of fluoride and arsenic were suitable for the Langmuir and Freundlich models. Moreover, As for fluoride and arsenic, the increase rate of adsorption concentration decreased after 8 and 12 hr, respectively, after the start of the reaction. Also, the thermodynamic data showed that the amount of fluoride and arsenic adsorbed onto ASBA increased with increasing temperature from 25 degrees C to 35 degrees C, indicating that the adsorption was endothermic and non-spontaneous reaction. As a result of regeneration experiments, ASBA can be regenerated by 1N of NaOH. In the actual mine drainage experiment, it was found that it has relatively high removal rates of 77% and 69%. The experimental results show ASBA is effective as an adsorbent for removal fluoride and arsenic from mine drainage, which has a small flow rate and acid/neutral pH environment.

A proper waste management practice such as anaerobic digestion for the waste generated by the agro-food industries could minimize the amount of material disposal to landfill. In our study, the improvement of methane production was elucidated through the pretreatment optimization of the mixed fruit wastes (FW). Dilute acetic acid pretreatment of FW was optimized in order to increase the bioavailability and microbial accessibility. A maximum sugar recovery of 95% was achieved from the pretreated FW under the optimized conditions (0.2 M acetic acid, 62.5 degrees C, and 30 min). Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric (TG) analyses verified the presence of cellulosic material in the pretreated FW. X-ray diffraction (XRD) analysis indicated that the crystallinity index was increased to 56% after the disruption of complex hemicellulosic structures during pretreatment. Increased porosity and surface roughness of pretreated FW for better microbial attachment were confirmed in scanning electron microscopy (SEM). Anaerobic digestion showed increased methanogenic activity (10.17 mL g(-1) VSinitial d(-1)) in pretreated FW, during 86-day experimental period due to better microbial attachment and accessibility during the digestion process. Higher methane yield of 53.58 mL g(-1) VSinitial was observed in pretreated FW. Thus, acetic acid pretreatment is an effective method to improve the utilization and conversion of FW to methane. (C) 2018 Elsevier Ltd. All rights reserved.

Alginate beads (ABs) immobilized with hydrous zirconium oxide (ZO) were used as a hybrid adsorbent (ZO@AB) for the effective removal of copper ions [Cu(II)] from aqueous phase. ZO@AB was characterized using X‐ray photoelectron spectroscopy to confirm the impregnation of ABs with ZO and the adsorption of Cu(II) onto ZO@AB. The maximum equilibrium sorption capacity of ZO@AB for Cu(II) was 63.1 mg·g−1 at pH 5. The Cu(II) removal rate was high at the beginning of reaction, with >90% adsorption within 24 hours, and equilibrium was achieved within 48 hours. The adsorption of Cu(II) onto ZO@AB was well described by pseudo‐second‐order kinetic model (R2 > 0.99), and the monolayer nature of sorption was supported by the Langmuir model (R2 > 0.99). The sorption process was endothermic, favorable, and spontaneous in nature. Regarding the reusability of the adsorbent, its sorption capacity remained satisfactory (>90%) throughout the 5 consecutive cycles (regeneration in 0.1 mol·L−1 HCl). The stoichiometric ratio of released calcium ions [Ca(II)] to adsorbed copper ions [Cu(II)] was approximately 1:1, confirming that ion exchange was the main mechanism for removal of Cu(II) from aqueous phase. The developed adsorbent (ZO@AB) shows promise as a candidate for the effective and selective removal of Cu(II) from aqueous phase.

Column tests of a sulfate reducing bacteria (SRB) bioreactor were conducted to determine the design factors for sulfate-rich mine drainage. Various substrates were applied to the bioreactor, including cow manure and its mixture with a mushroom compost, with rice straw and limestone as subsidiary materials. This procedure provided a removal efficiency of up to 82% of the total sulfur with the mixture of cow manure (70%), mushroom compost (10%) and rice straw (20%), and higher efficiencies were observed after 2 days of retention time. In the downflow condition of the flow direction, oxygen supply and re-oxidation of the sulfates occurred, causing a decrease in sulfate removal efficiency. The addition of an inorganic sludge containing heavy metals, which was intended for production of metal-sulfides in the bioreactor, had a negative effect on the long-term operation owing to arsenic release and toxicity to the SRB. The results thus show that a bioreactor using a mixed substrate with cow manure and operating in the downflow direction could reduce sulfates and total dissolved sulfur content; this process confirms the applicability of the SRB bioreactor to sulfate-rich saline drainage.

Methyl paraben (MP), a widely used preservative, exhibits endocrine-disrupting properties with estrogenic activities. The aqueous phase degradation of MP, using UV-activated persulfate method, was investigated in the present study. The combination of UV irradiation and persulfate anion successfully degraded MP showing 98.9% removal within 90min. A quenching experiment using ethanol (EtOH) and tert-butyl alcohol (TBA) showed the presence of both radicals (OH and SO4–) in the system; near neutral pH SO4– radical was the major species. The influence of various factors such as persulfate dose, initial MP concentration, solution pH, and water matrix components on the degradation kinetics was examined in view of the practical applications of the developed process. The degradation rate of MP was considerably increased as the amount of persulfate increased. The degradation of MP in the UV/persulfate system was pH dependent and more promising near neutral pH (6.5) conditions. The presence of anions such as Cl−, HPO42− and HCO3− showed inhibitory effect towards MP degradation. The presence of humic acid also suppressed the degradation efficiency of MP. The reaction rate followed pseudo-first-order kinetics for all of the degradations. The degradation of MP by UV/persulfate treatment led to the production of seven transformation byproducts, which were identified using ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS). A degradation pathway for MP degradation was also proposed. The results of the present study reveal that the UV/persulfate process could be an effective approach to remove MP from aqueous solutions.

The effectiveness of silicate- and phosphate-based surface coating agents (Na2SiO3, CaSiO3, and KH2PO4) in inhibiting the oxidation of sulfide minerals in acidic and low temperature conditions was studied. Rock samples were coated using two oxidation methods: H2O2 was mixed with the coating agents in one, whereas in the second, H2O2 was applied to the rock surface prior to the coating agent. The second approach was ineffective, but with Method 1, the pH (5) was above the pH (3.6) of the uncoated control sample. Oxidation, calculated after 14 weeks, had been suppressed by up to 96 and 65%, as indicated by the release of Fe2+ and SO4 2−, respectively. All three coating agents (at concentrations of 0.1 and 0.3 M) suppressed the release of Fe2+ (<3 mg L− 1). Na2SiO3 inhibited Fe2+ and SO4 2− release by 94 and 65%, respectively. Surface protection (or oxidation inhibition) efficiencies of KH2PO4 (in terms of Fe2+ release) were 67, 94, and 96% with 0.05, 0.1, and 0.3 M, respectively. The Na2SiO3 and CaSiO3 coatings, irrespective of their concentrations, reduced iron oxidation by 94 and 84%, respectively. Fourier transform infrared spectroscopy analysis of the Na2SiO3 treated samples showed the presence of iron silicate coatings. Based on this work, coating of rock samples with silicate or phosphate can reduce the oxidation rate of sulfide minerals in acidic and low temperature conditions.

Applicability of a powdered activated carbon impregnated alginate beads (ABPAC) was examined toward simultaneous removal of heavy metal (cadmium) and volatile organic compound (benzene) from water. Sorption of cadmium and benzene by ABPAC was investigated in both single and binary systems as a function of contact time (1h–11d), initial pH (4–7), and initial concentration of cadmium and benzene (10–600mgL–1). The sorption capacity of APBAC for cadmium and benzene was 149.32 and 89.60mgg–1, respectively. Sorption kinetics was well described by the pseudo-second-order model with correlation coefficients, R2>0.994. Cadmium sorption capacity increased from 41.76 to 56.09mgg–1 with increasing pH from 4 to 7, while benzene sorption was not much influenced. The Langmuir model best correlated with adsorption of cadmium and benzene on ABPAC. Our results indicated no competition effects in a binary-contaminant system, which proves the practical utility of ABPAC for the concurrent sorptive removal of aqueous phase heavy metals and volatile organic compounds.

본 연구는 현장규모에서 자체 제작된 현장시험장치를 이용하여 토양과 공기 중 석면함량의 상관관계를 분석하고자 하였다. 현장에서 8 m/s, 11 m/s, 15 m/s 및 18 m/s의 다양한 풍속에 의한 석면의 비산 정도를 측정하였다. 토양시료는 편광현미경법과 주사전자현미경법 및 X-선분광분석을 하였으며, 대기 시료는 위상차현미경법을 이용하였다. 실험결과, 현장시험장치의 작동성 및 편의성이 입증되었으며, 풍속이 증가할수록 비산되는 공기 중 석면 농도가 증가하는 뚜렷한 양의 상관관계가 나타난 반면, 토양 습도가 증가할수록 비산되는 공기 중 석면 농도는 감소하는 음의 상관관계가 나타났다. 특히 토양의 석면함량이 3∼6%인 경우, 토양습도와 풍속의 조건에 따라 실내 공기질 권고 기준을 초과하는 경우가 나타났다. 따라서, 토양 내 석면의 함량이 약 3% 이상인 곳을 우선적으로 복원해야 할 것으로 판단된다.

This research was undertaken to evaluate the feasibility of granular ferric hydroxide (GFH) for fluoride removal from aqueous solutions. Batch experiments were performed to study the influence of various experimental parameters such as contact time (1min–24h), initial fluoride concentration (1–100mgL−1), temperature (10 and 25°C), pH (3–12) and the presence of competing anions on the adsorption of fluoride on GFH. Kinetic data revealed that the uptake rate of fluoride was rapid in the beginning and 95% adsorption was completed within 10min and equilibrium was achieved within 60min. The sorption process was well explained with pseudo-first-order and pore diffusion models. The maximum adsorption capacity of GFH for fluoride removal was 7.0mgg−1. The adsorption was found to be an endothermic process and data conform to Langmuir model. The optimum fluoride removal was observed between pH ranges of 4–8. The fluoride adsorption was decreased in the presence of phosphate followed by carbonate and sulphate. Results from this study demonstrated potential utility of GFH that could be developed into a viable technology for fluoride removal from drinking water.

The purpose of this study was to investigate the feasibility of As(V) reduction by aqueous Fe(II), and subsequent As(III) immobilization by the precipitation of As(III) incorporated magnetite-like material [i.e., co-precipitation of As(III) with Fe(II) and Fe(III)]. Experimental results showed that homogeneous As(V) reduction did not occur by dissolved Fe(II) at various pH values although the thermodynamic calculation was in favor of the redox reaction between As(V) and Fe(II) under the given chemical conditions. Similarly, no heterogeneous reduction of sorbed As(V) by sorbed Fe(II) was observed using synthetic iron (oxy)hydroxide (Goethite, -FeOOH) at pH 7. Experimental results for the effect of As(V) on the oxidation of Fe(II) by dissolved oxygen showed that As(V) inhibited the oxidation of Fe(II). These results indicate that As(V) could be stable in the presence of Fe(II) under the anoxic or subsurface environments.

Adsorption study with untreated and zinc chloride (ZnCl2) treated coconut granular activated carbon (GAC) for nitrate removal from water has been carried out. Untreated coconut GAC was treated with ZnCl2 and carbonized. The optimal conditions were selected by studying the influence of process variables such as chemical ratio and activation temperature. Experimental results reveal that chemical weight ratio of 200% and temperature of 500 degrees C was found to be optimum for the maximum removal of nitrate from water. Both untreated and ZnCl2 treated coconut GACs were characterized by scanning electron microscopy (SEM), Brunauer Emmett Teller (BET) N-2-gas adsorption, surface area and Energy Dispersive X-Ray (EDX) analysis. The comparison between untreated and ZnCl2 treated GAC indicates that treatment with ZnCl2 has significantly improved the adsorption efficacy of untreated GAC. The adsorption capacity of untreated and ZnCl2 treated coconut GACs were found 1.7 and 10.2 mg/g, respectively. The adsorption of nitrate on ZnCl2 treated coconut GAC was studied as a function of contact time, initial concentration of nitrate anion, temperature, and pH by batch mode adsorption experiments. The kinetic study reveals that equilibrium was achieved within one hour. The adsorption data conform best fit to the Langmuir isotherm. Kinetic study results reveal that present adsorption system followed a pseudo-second-order kinetics with pore-diffusion-controlled. Results of the present study recommend that the adsorption process using ZnCl2 treated coconut GAC might be a promising innovative technology in future for nitrates removal from drinking water.