PHOTOCATALYTIC REMOVAL OF TR I- AND HEXA-VALENT CHROMIUM IONS FROM CHROME-ELECTROPL ATING WASTEWATER

A novel technique based on photocatalysis was applied to eliminate chromium ions, a toxic hazardous environmental pollutant. The photoreduction of each species of chromium (total, hexavalent, and trivalent chromiums) from chrome-electroplating wastewater was investigated using a titanium dioxide suspension under irradiation by a low-pressure mercury lamp. The initial concentration of total chromium was 300 mg/l. The applied conditions were the direct photocatalytic reduction process at pH 3.65 and the indirect photocatalytic reduction with added hole scavengers at the same solution pH. Results from both processes were comparatively discussed. Result show that chromium was not efficiently removed by direct photoreduction. In contrast, with the adding of hole scavengers, which were formate ions, the photoreduction of chromium was very favorable. Both hexavalent and trivalent chromiums were efficiently removed. The photocatalytic mechanism is purposed in this study

Municipal Solid Waste Recovery and Recycling

© 2014 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. Recycling is a series of activities that includes collecting recyclable materials that would otherwise be considered waste, sorting, and processing recyclables into raw materials, and manufacturing them into new products. In this chapter, the collection of recyclable materials in both developed and developing countries are reviewed. The physical and chemical recycling methods are also included with necessary engineering calculation. Finally, the marketing of recyclable materials is also depicted

จลนศาสตร์และไอโซเทอร์มการดูดซับอะทราซีนโดยไบโอชาร์ไม้ไผ่Kinetic and Isotherm Adsorption of Atrazine by Bamboo Biochar

งานวิจัยนี้มีวัตถุประสงค์เพื่อประเมินประสิทธิภาพการดูดซับอะทราซีนด้วยไบโอชาร์ที่สังเคราะห์จากไม้ไผ่ โดยศึกษาคุณสมบัติทางกายภาพและเคมีของไบโอชาร์ไม้ไผ่ และศึกษาระยะเวลาสมดุล ประสิทธิภาพการดูดซับ ไอโซเทอม รวมทั้งแบบจำลองจลนศาสตร์การดูดซับอะทราซีนของไบโอชาร์ไม้ไผ่ ด้วยการทดลองแบบกะ จากคุณสมบัติทางกายภาพและเคมี พบว่า ไบโอชาร์ไม้ไผ่มีค่า D50 เท่ากับ 200 ไมโครเมตร พื้นที่ผิวเท่ากับ 756.43 ตารางเมตรต่อกรัม และมีปริมาตรรูพรุนเท่ากับ 0.32 ลูกบาศก์เซนติเมตรต่อกรัม แสดงให้เห็นว่าเป็นวัสดุดูดซับแบบ Micropore เนื่องจากมีขนาดรูพรุนภายในเฉลี่ยเท่ากับ 1.69 นาโนเมตร นอกจากนั้นพบว่า มีการตรวจพบหมู่ฟังก์ชันของไฮดรอกซิล (O-H) ไฮโดรคาร์บอนประเภทอัลคิล (C-H) อะลิฟาติก (C-H) และอะโรมาติก (C=C) ที่ส่งผลต่อความสามารถในการดูดซับสารอะทราซีน ในส่วนการประเมินประสิทธิภาพในการดูดซับสารอะทราซีนพบว่า ให้ประสิทธิภาพในการดูดซับ 92.1 เปอร์เซ็นต์ หลังจากเข้าสู่ระยะเวลาสมดุลที่ 24 ชั่วโมง สอดคล้องกับสมการไอโซเทอร์มแบบฟรุนดิช โดยมีค่าคงที่สัมพันธ์กับความสามารถในการดูดซับ (KF) เท่ากับ 0.77 ไมโครกรัมต่อกรัม และการศึกษาแบบจำลองจลนศาสตร์การดูดซับชี้ให้เห็นว่าเป็นไปตามแบบจำลองอันดับที่สองเทียม ด้วยค่า R2 และ SSE เท่ากับ 0.9998 และ 0.0015 ตามลำดับ เมื่อพิจารณาค่าคงที่อัตราเร็วปฏิกิริยาอันดับสอง (K2) มีค่าเท่ากับ 0.1306 ไมโครกรัมต่อกรัมต่อนาที จึงสรุปได้ว่าการดูดซับอาศัยกลไกทั้งทางด้านกายภาพและเคมี ผลการทดลองทั้งหมดแสดงให้เห็นว่าไบโอชาร์ไม้ไผ่มีคุณภาพสูงในการเป็นวัสดุดูดซับสารอะทราซีน ซึ่งจัดเป็นวัดสุดูดซับที่มีต้นทุนต่ำสำหรับป้องกันสารเคมีทางการเกษตรออกสู่นอกพื้นที่และเข้ามาในพื้นที่This research aims to evaluate the adsorption efficiency of atrazine using biochar synthesized from bamboo. The study primarily focuses on these aspects: bamboo biochar physical and chemical properties, the equilibrium time, adsorption efficiency, isotherm as well as adsorption kinetic model with batch testing. Regarding physical and chemical properties, bamboo biochar exhibited the D50 of 200 μm, surface area of 756.43 m2/g, average pore size of 1.69 nm and pore volume of 0.32 cm3/g. Considering these properties, the substance can be defined as a microporous carbon adsorbent. Also, the functional groups of bamboo biochar show the groups of hydroxyls (O-H), alkyl (C-H), aliphatic (C-H), and aromatic carbon (C=C), which have a positive effect on adsorption of atrazine. Form the evaluation of atrazine adsorption properties, the bamboo biochar has the adsorption efficiency of 92.1% after 24 h equilibrium time, corresponding to the Freundlich adsorption isotherm. The Freundlich constant (KF) is 0.77 μg/g. In term of adsorption kinetic model, the results indicated being the pseudo second order reaction kinetics with R2 value and SSE are 0.9998 and 0.0015, respectively. The pseudo-second order rate constant (K2) shows 0.1306 μg/g.min. This can be concluded that the adsorption of bamboo biochar used both physical and chemical mechanisms. Overall results indicated that bamboo biochar can be used as an effective, low-cost adsorbent for atrazine removal. Thus, the biochar can be used as a chemical barrier for controlling agrochemical contaminants into agricultural land

Green Ag/AgCl as an Effective Plasmonic Photocatalyst for Degradation and Mineralization of Methylthioninium Chloride

A green synthesis of Ag/AgCl with an exceptional SPR and photocatalysis property is greatly benefit to the environmental application especially pollutant removal. In this work, a novel green plasmonic photocatalysis of Ag/AgCl nanocatalyst using aqueous garlic extract (Allium Sativum L.) was successfully synthesized. The allicin and organosulfur compounds in the garlic can act as reducing agents in the green synthesis process. The nanocatalyst properties were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffractometer. The light-harvesting property was investigated by UV-vis absorption spectra which reveals its visible light absorption capability owing surface plasmon resonance behavior of Ag nanoparticles. The degradation and mineralization of methylthioninium chloride (MC) using this photocatalyst were evaluated under visible light and natural solar irradiation. Surface plasmon resonance of Ag nanoparticles and the presence of organosulfur from the garlic extract facilitated adsorption of MC onto the particle surface, promoting greater degradation. The photocatalytic reaction under visible light can be explained by the pseudo first-order pattern with the highest reaction rate of 0.5829 mg L−1 min−1 at pH 10. The photocatalytic activity of the Ag/AgCl under the natural sunlight reached 90% and 75% for MC and total organic carbon (TOC), respectively. The intermediate products detected during MC degradation under sunlight irradiation before final transformation to CO2, H2O, HNO3, and H2SO4 were also reported. The simplicity of Ag/AgCl green synthesis with the photocatalysis properties under visible light and sunlight can offer the convenience of applying these nanoparticles for pollutant removal in water treatment processes

Identification of Active Species in Photodegradation of Aqueous Imidacloprid over g-C₃N₄/TiO₂ Nanocomposites

In this work, g-C3N4/TiO2 composites were fabricated through a hydrothermal method for the efficient photocatalytic degradation of imidacloprid (IMI) pesticide. The composites were fabricated at varying loading of sonochemically exfoliated g-C3N4 (denoted as CNS). Complementary characterization results indicate that the heterojunction between the CNS and TiO2 formed. Among the composites, the 0.5CNS/TiO2 material gave the highest photocatalytic activity (93% IMI removal efficiency) under UV-Vis light irradiation, which was 2.2 times over the pristine g-C3N4. The high photocatalytic activity of the g-C3N4/TiO2 composites could be ascribed to the band gap energy reduction and suppression of photo-induced charge carrier recombination on both TiO2 and CNS surfaces. In addition, it was found that the active species involved in the photodegradation process are OH• and holes, and a possible mechanism was proposed. The g-C3N4/TiO2 photocatalysts exhibited stable photocatalytic performance after regeneration, which shows that g-C3N4/TiO2 is a promising material for the photodegradation of imidacloprid pesticide in wastewater

Airborne Pesticides—Deep Diving into Sampling and Analysis

The escalating utilization of pesticides has led to pronounced environmental contamination, posing a significant threat to agroecosystems. The extensive and persistent global application of these chemicals has been linked to a spectrum of acute and chronic human health concerns. This review paper focuses on the concentrations of airborne pesticides in both indoor and outdoor environments. The collection of diverse pesticide compounds from the atmosphere is examined, with a particular emphasis on active and passive air sampling techniques. Furthermore, a critical evaluation is conducted on the methodologies employed for the extraction and subsequent quantification of airborne pesticides. This analysis takes into consideration the complexities involved in ensuring accurate measurements, highlighting the advancements and limitations of current practices. By synthesizing these aspects, this review aims to foster a more comprehensive and informed comprehension of the intricate dynamics related to the presence and measurement of airborne pesticides. This, in turn, is poised to significantly contribute to the refinement of environmental monitoring strategies and the augmentation of precise risk assessments

Heterogeneous Fenton and Photo-Fenton Reactions in Paraquat Removal Using Iron Nanoparticles

© 2016 Inderscience Enterprises Ltd. This work was aimed to investigate the ability of iron nanoparticles in paraquat degradation using heterogeneous Fenton and photo-Fenton processes. The iron nanoparticles were synthesised and their sizes are in the nanometre range of 10-30 nm. SEM, TEM, and XRD were used to characterise the obtained materials. From XRD analysis and the Fe(II)/Fe(III) ratio, the iron nanoparticles are predominantly of magnetite phase. Results from Fenton reaction at pH3 show that paraquat with initial concentrations in range of 60-100 ppm has been degraded with the removal percentages in the range of 43.7-75.8%. In photo-Fenton process at pH3, the paraquat removal percentages were 70.9-99.1% for initial paraquat concentrations as of 100-300 ppm. The photo-Fenton reaction using iron nanoparticles provided higher efficiency in paraquat removal than the Fenton process. Results from this work can benefit further for application of iron nanoparticles in pesticides removal from water and wastewater