Decolorization of RhB dye by manganese oxides: effect of crystal type and solution pH

Abstract

BackgroundOrganic dye pollution in water has become a major source of environmental pollution. Mn(III/IV) oxides have attracted a great deal of attention to remove organic dye pollutants due to their unique structures and physicochemical properties. Numerous studies have reported the removal of dye by various Mn(III/IV) oxides through catalytic degradation and adsorption. The crystalline structures of manganese oxides and solution pH may exert substantial impact on the removal of dyes. However, few studies have focused on the oxidative degradation of RhB dye using Mn(III/IV) oxides with different crystal structures during a spontaneous reaction. In the present study, three manganese oxides with different crystal type (α-MnO2, β-MnO2, and δ-MnO2) were prepared by refluxing process to decolorize RhB dye in various pH solutions.ResultsThe results showed that the decolorization efficiencies of RhB for the three manganese oxides all increase with decrease solution pH. α-MnO2 exhibited highest activity and could efficiently degrade RhB at pH 2–6. The degradation of RhB by β-MnO2 and δ-MnO2 could be observed at pH 2–3, and only little adsorption RhB on manganese oxides could be found at pH 4–6. The UPLC/MS analysis suggests that the decolorization of RhB by manganese oxides consists of three main stages: (1) cleavage of the ethyl groups from RhB molecular to form Rh; (2) further destruction of –COOH and –CNH2 from Rh to form the small molecular substances; (3) mineralization of the small molecular substances into CO2, H2O, NO3− and NH4+.ConclusionsOverall, these results indicate that α-MnO2 may be envisaged as efficient oxidants for the treatment of organic dye-containing wastewater under acid conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12932-015-0024-2) contains supplementary material, which is available to authorized users.

Preparation of aerochitin‐TiO2 composite for efficient photocatalytic degradation of methylene blue

“…These organic pollutants contribute directly to water pollution and one of the major problems concerning organic pollutants is colored dyestuffs. These colored dyestuffs may be carcinogenic and mutagenic to humans and aquatic organisms . The wastewater treatment methods applied for the industrial effluents include coagulation flocculation, electro chemical oxidation, biodegradation, ion exchange, ozonation, and adsorption by activated carbon .…”

Sintesis MnO2 Lapisan Nipis Poros menggunakan Templat Silika Alumina-Aptes: Aplikasi Penjerapan Pewarna

“…Penjerapan pewarna dengan menggunakan penjerap logam oksida telah banyak dilakukan dan keputusan kajian menunjukkan keberkesanan yang tinggi bagi logam oksida (CuO, MnO 2 , Mn 2 O 3 , MnOOH) sebagai penjerap terhadap pewarna yang berbeza (Abdullah & Wong 2010;Cao et al 2011;Chen & He 2008;Chen et al 2013;Cui et al 2015;Fei et al 2008;Ge & Qu 2003). Jenis kristal logam oksida dan pH larutan memainkan peranan dalam aktiviti penjerapan pewarna oleh penjerap dengan kumpulan Cui et al (2015) Ujian penjerapan dilakukan dengan menggunakan tiga jenis pewarna berbeza yang terdiri daripada kumpulan anionik iaitu pewarna remazol merah (reaktif), eriokrom hitam (asid) dan kationik iaitu metilena biru (bes) menggunakan kaedah kelompok. Sebanyak 0.2 g penjerap seperti silika alumina, silika alumina-APTES, komposit silika aluminaMnO 2 dan MnO 2 lapisan nipis digunakan dalam ujian penjerapan pewarna dalam tempoh masa sehingga selama 120 min pada suhu bilik serta pH asal larutan.…”

Preparation of a PANI/ZnO Composite for Efficient Photocatalytic Degradation of Acid Blue

“…Afterward, the typical photocatalysis mechanism for metal-oxides proceeds, i.e., e CB − and h VB + transform H 2 O and O 2 into OH −1 radicals which in turn degrade the organic pollutants [24,25]. Furthermore, many organic pollutants (e.g., dyes) are industrial effluents generated from various sources [26,27,28]. So, photocatalysis has emerged as a potential strategy to degrade dyes in wastewater [29,30].…”