Developing persulfate-activator soft solid (PASS) as slow release oxidant to remediate phenol-contaminated groundwater

The research objective was to develop a persulfate-activator soft solid (PASS) as a biodegradable slow-release oxidant to treat phenol-contaminated groundwater. PASS was prepared by graft copolymerization of acrylic acid (AA) and acrylamide (AM) onto 1% (w/v) sodium alginate mixed with 500 mg L−1 sodium persulfate and 5 mg L−1 ferrous sulfate. The physical and chemical properties of PASS were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, the water content and swelling ratio. Various variables, including the ratio of AA/AM, pH, temperature and the type of groundwater cations affecting PS release, were investigated. The maximum PS release in DI water was 98% in the ratio of PASS 1 (AA/AM, 75/25), 96% at pH 3, 83% at 25 °C, and 80% with Na+. The major factors controlling PS release were the AA/AM ratio and pH. PASS 1 can be stable in size and shape for 6–8 days and completely degraded within 34 days. The degradation rates of 10 mgL−1 phenol using PASS produced the highest kobs values for each variable at a ratio of PASS 1 (k = 0.1408 h−1), pH 7 (k = 0.1338 h−1), 25 °C (k = 0.1939 h−1), and Ca2+ (k = 0.1336 h−1). The temperature of the groundwater was key to driving the reaction between PS and phenol. PASS 1 was applied in simulated phenol-contaminated groundwater via horizontal tanks containing Ottawa sand. The results indicated 93.2% phenol removal within 72 h in a narrow horizontal flow tank and 41.7% phenol removal in a wide horizontal flow tank with aeration

Formulation of zeolite supported nano-metallic catalyst and applications in textile effluent treatment

Textile industry is one of the major industries worldwide and produces a huge amount of coloured effluents. The presence of coloured compounds (dyes) in water change its aesthetic value and cause serious health and environmental consequences. However, the present investigation was carried out to minimize and reduce the colour compounds discharged by the textile industries through a nano-scaled catalyst. This study is mainly focused on the explanation of nanoparticles aggregation by deposition on natural zeolite, and utilization of this natural zeolite as supported material to nano zerovalent iron (NZ-nZVI) in the form of liquid slurry with sodium percarbonate acting as an oxidant in a Fenton like system for the removal of synthetic CI acid orange 52 (AO52) azo dye, in textile effluent. The nano-scaled zerovalent irons were synthesized by borohydride method in ethanolic medium. UV–vis spectrophotometry, FTIR, EDX, SEM, and XRD (powdered) analysis were used for the investigations of surface morphology, composition, and properties of natural zeolite supported nZVI and study the dye removal mechanism. The XRD spectrum revealed that clinoptilolite is the major component of natural zeolite used, while EDX found that the iron content of NZ-nZVI was about 9.5 %. The introduction of natural zeolite as supporting material in the formation of iron nanoparticle resulted in the partial reduction of aggregation of zerovalent iron nanoparticles. The findings revealed that the 94.86 % removal of CI acid orange 52 dye was obtained after 180 min treatment at 15 mg/L initial dye concentration. The highest rapid dye removal of about 60 % was achieved within the first 10 min of treatment at the same dye concentration. Furthermore, the actual dyeing effluent including green, magenta, and the blended colour was successfully decolourized by natural zeolite-supported nZVI/SPC Fenton process. It is concluded that the acceleration of corrosion of NZ-nZVI, breaking of azo bond, and consumption of Fe2+ were the possible mechanisms behind the removal of AO52 dye. It is also recommended that NZ-nZVI/SPC Fenton process could be a viable option for effluent and groundwater remediation

Remediating chloroacetanilide -contaminated water using zerovalent iron

Pesticide spills and discharges can result in ground and surface water contamination. Simple iron treatment provides an effective and inexpensive remediation tool for soil and water contaminated with chloroacetanilide herbicides. We found the effectiveness of zerovalent iron (Fe0) to dechlorinate aqueous metolachlor (2-chloro-N-(2-ethyl-6-methyl phenyl)- N-(2-methoxy-1-methyl ethyl) acetamide) was greatly enhanced in the presence of Al, Fe(II) or Fe(III) salts, with the following order of destruction kinetics observed: Al2(SO4)3 \u3e AlCl 3 \u3e Fe2(SO4)3 \u3e FeCl3. A common observation was the formation of green rusts, mixed Fe(II)/Fe(III) hydroxides with interlayer anions that impart a greenish-blue color. The mechanism responsible for enhanced metolachlor loss may be related to the role these salts play in facilitating Fe(II) release. To investigate this catalytic effect, we characterized changes in Fe0 composition during the treatment of metolachlor. Raman microscopic analysis and X-ray diffraction indicated that the iron source was initially coated with a thin layer of magnetite (Fe3O4), maghemite (γ-Fe 2O3), and wüstite (FeO). Temporal mineralogical analysis indicated akaganeite (β-FeOOH), goethite (α-FeOOH), magnetite, and lepidocrocite (γ-FeOOH) formed in the Fe0-metolachlor suspension when Al2(SO4)3 or FeSO4 were present. Green rust II (Fe6(OH)12SO4) was also transiently identified in Fe0 treatments containing FeSO4. Although conditions favoring green rust formation in a Fe 0-batch system increased metolachlor dechlorination, we determined that green rust itself can only marginally contribute to transforming metolachlor. In contrast, metolachlor dechlorination was observed in a batch system containing magnetite or goethite and FeSO4 at pH 8. These results indicate that creating conditions favoring green rust facilitate Fe0-mediated dechlorination of metolachlor by providing an available source of Fe(II)/Fe(III) and generating iron oxide surfaces that can coordinate Fe(II). This information can be useful in designing and managing Fe0-treatment systems

การแยกซิลิกาจากเถ้าลอยชีวมวลด้วยวิธีไฮโดรเทอร์มัลในสภาวะเบสและการตกตะกอนซิลิกาด้วยกรดอินทรีย์Extracting Silica from Biomass Fly Ash by Using Alkaline Hydrothermal Treatment and Silica Precipitation by Using Organic Acids

งานศึกษานี้มีวัตถุประสงค์เพื่อศึกษาสภาวะเหมาะสมในการแยกและตกตะกอนซิลิกาจากเถ้าลอยชีวมวล ผลการศึกษาพบว่าสภาวะที่ดีที่สุดในการแยกซิลิกาจากเถ้าลอยในงานศึกษานี้ คือ การกระตุ้นเถ้าลอยด้วยสารละลายโซเดียมไฮดรอกไซด์ที่มีความเข้มข้น 3 โมลาร์ อัตราส่วนระหว่างเถ้าลอยและสารละลายที่ใช้ 1 : 10 กรัมต่อมิลลิลิตร ที่อุณหภูมิ 90oC เป็นเวลา 24 ชั่วโมง ผลการศึกษาชี้ว่าปัจจัยเหล่านี้มีความสำคัญต่อการละลายของซิลิกาจากเถ้าลอยชีวมวล การศึกษาการตกตะกอนซิลิกาด้วยสารละลายกรดอินทรีย์พบว่าการใช้กรดซิตริกและสภาวะการตกตะกอนที่ pH เท่ากับ 4 เป็นสภาวะที่ทำให้ซิลิกาตกตะกอนสูงสุด (ร้อยละ 98.5) ซึ่งเป็นเพราะสภาวะความเป็นกรดที่เพียงพอในการตกตะกอนและกรดอินทรีย์มีค่าการแตกตัวที่เหมาะสม ซิลิกาที่ผลิตได้ทำการวิเคราะห์ด้วยเครื่อง X-ray Diffraction และพบว่าเป็นซิลิกาแบบอสัณฐานการวิเคราะห์ด้วยเครื่อง X-ray Fluorescence พบว่าผลิตภัณฑ์ที่ได้มีซิลิกาเป็นองค์ประกอบหลักที่ร้อยละ 95.6 ดังนั้นการนำเถ้าลอยชีวมวลมาเป็นวัตถุดิบในการผลิตซิลิกาจึงเป็นแนวทางที่จะเพิ่มมูลค่าให้กับเถ้าลอยชีวมวลได้อย่างน่าสนใจThis study aims to investigate the optimal condition to extract and precipitate silica from biomass fly ash. Results showed that the best condition to extract silica from fly ash in this study was by treating fly ash with 3M NaOH solution using fly ash-to-solution ratio of 1 : 10 g/ml at 90oC for 24 h. The findings indicate that these studied variables are of importance to the dissolution of silica from biomass fly ash. In the study on precipitating silica using organic acid solution, results showed that the use of citric acid and precipitation condition at pH of 4 were the appropriate conditions by giving the maximum silica precipitation (98.5%). This was because of sufficient acidic conditions to precipitate silica and the appropriate dissociation constant of organic acid. The obtained silica was analyzed by using X-ray diffraction was amorphous silica. X-ray fluorescence analysis showed that the obtained product was mainly composed of silica at 95.6%. Therefore, the use of biomass fly ash as a raw material for silica production is an interesting way to enhance value for biomass fly ash

Transformation of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Permanganate

The chemical oxidant permanganate (MnO4−) has been shown to effectively transform hexa-hydro-1,3,5-trinitro-1,3,5-triazine (RDX) at both the laboratory and fieldscales. We treated RDX with MnO4− with the objective of quantifying the effects of pH and temperature on destruction kinetics and determining reaction rates. A nitrogen mass balance and the distribution of reaction products were used to provide insight into reaction mechanisms. Kinetic experiments (at pH ~7, 25 °C) verifiedthat RDX−MnO4− reaction was first-order with respect to MnO4− and initial RDX concentration (second-order rate: 4.2 × 10−5 M−1 s−1). Batch experiments showed that choice of quenching agents (MnSO4, MnCO3, and H2O2) influenced sample pH and product distribution. When MnCO3 was used as a quenching agent, the pH of the RDX−MnO4− solution was relatively unchanged and N2O and NO3− constituted 94% of the N-containing products after 80% of the RDX was transformed. On the basis of the preponderance of N2O produced under neutral pH (molar ratio N2O/NO3 ~5:1), no strong pH effect on RDX−MnO4− reaction rates, a lower activation energy than the hydrolysis pathway, and previous literature on MnO4− oxidation of amines, we propose that RDX−MnO4− reaction involves direct oxidation of the methylene group (hydride abstraction), followed by hydrolysis of the resulting imides, and decarboxylation of the resulting carboxylic acids to form N2O, CO2, and H2O