Facile synthesis, growth process, characterisation of a nanourchin-structured α-MnO2 and their application on ultrasonic-assisted adsorptive removal of cationic dyes: A half-life and half-capacity concentration approach

Abstract

Textile dyes pose a serious threat in terms of water pollution due to its complex aromatic structures and poor degradability. In order to reduce the toxic effects of Crystal Violet (CV) and Methylene Blue (MB), an ultrasonic-assisted dye adsorption using urchin like α-MnO nanostructures was studied. The adsorbent was synthesised by hydrothermal method at low-temperature. The crystallinity and morphology were determined to investigate the growth mechanism of α-MnO nanourchins which consists of two main stages. The initial stage includes the formation of α-MnO microspheres followed by the epitaxial growth of nanoneedles on to the surface of them. The α-MnO was characterised by BET, XRD, FT-IR, XPS, SEM, TEM and TGA. At 5.6, the point of zero charge of α-MnO nanostructures was determined. The total pore volume and average pore radius were confirmed to be 4.751 × 10 cc/g and 10.99 Å respectively from the BET analysis. Batch adsorption experiments were performed to investigate the effect of pH, adsorbent dosage, sonication time, initial dye concentration, temperature, ultrasonic frequency and power. The adsorption mechanism was studied using several isotherm and kinetic models. The adsorption data of CV and MB at equilibrium was observed to adopt the Langmuir isotherm model and pseudo-second order kinetic model. The maximum adsorption capacities for CV and MB were found to be 5882.3 and 5000 mg/g respectively. The thermodynamic study predicted that the process was exothermic for CV and endothermic for MB. The effects of competitive ions, ionic strength and humic acid on the uptake of both the dyes were also investigated. And finally, the reusability of recovered α-MnO after dye adsorption was studied up to five cycles for its potential industrial applications.

Preparation and characterization of MnO2-based nanoparticles at different annealing temperatures and their application in dye removal from water

“…The literature review suggested that significant research over the aqueous media has been conducted to remove numerous dyestuffs including methylene blue from waters. Among the most commonly employed methods for decolorization and removal of dyes include both traditional treatment and non-traditional methods, e.g., adsorption (Abraham et al 2018;Jamal et al 2016;Shim et al 2019;Xiong et al 2020), biological treatments (Jafari et al 2017;Wang et al 2012), biosorption (Sebeia et al 2019;Zhai et al 2019), electro-coagulation (de Carvalho et al 2015Nippatla and Philip 2019), advanced oxidation processes (Bao et al 2018;Kang et al 2019;Liang et al 2012;Qu et al 2014), photocatalytic degradation (Gagrani et al 2018;Nanda et al 2016;Zhao et al 2018), ozonation (Hama Aziz et al 2018, chemical precipitation and membrane technology (Ghaemi and Safari 2018;Liu et al 2018), ultrafiltration (Ouni and Dhahbi 2010), ceramic membrane-based technologies on amorphous silica (Abdelrazek and Barakat 2016) and also degradation based on sonochemical method (Abbasi and Asl 2008). However, complete removal of dyes along with their derivatives is still a challenge with single or traditional treatment by which the decolorization can be achieved.…”

Adsorption Behaviour of Reactive Blue 194 on Raw Ramie Yarn in Palm Oil and Water Media

“…Langmuir [ 37 ] (Equation (7)) and Freundlich [ 38 ] (Equation (8)) isotherms are widely used in fitting the dye adsorption in textile dyeing. where [ D ] f (g g − 1 ) and [ D ] s (g L − 1 ) are the dye concentration in the fibre and dye solution at equilibrium time; [ S ] f (g g − 1 ) is the Langmuir constant related to adsorption capacity; K L is the Langmuir equilibrium constant.…”

Preparation of MnO2 Loaded Hydrothermal Carbon-coated Electrospun PAN Fiber Membranes for Highly Efficient Adsorption and Separation of Cationic Dye

“…It has been reported that nano-sized MnO2 and hydrothermal carbon have good adsorption properties for organic dyes [65,66] . The characterization proved that we have prepared MnO2 loaded hydrothermal carbon-coated PAN nanofiber membranes successfully and the AC/MnO2/PAN nanofibers had excellent adsorption capacity for cationic dyes.…”