Dyes which are used in textile and leather industries, commercial goods, and laboratories play a crucial role in accumulating lethal components in the water bodies, thereby affecting the environment. Though various physicochemical methods have been adopted for eradication of dyes, adsorption using biomass has gained more attention due to their high efficacy of removal in an eco-friendly manner. This investigation aims to analyze the effectiveness of pre-treated Lemna minor biomass in removing methyl orange dye in aqueous solution. Additionally, the study explores the ecotoxicity of the acid–alkali-treated Lemna minor biomass using an earthworm model. Collected biomass was pretreated by acid–alkali treatment which brought about characteristic changes in the structural and functional properties of biomass. Batch adsorption experiments demonstrated that the pretreated biomass effectively adsorbed the dye, with the adsorption rate significantly affected by factors such as dosage, pH, and temperature. Optimum adsorption was recorded at 500 mg of adsorbent, pH 7 and 40 °C temperature. Among the various isotherm models, Langmuir isotherm is the best fitting isotherm model. Thermodynamic studies were evaluated from 303.15 to 323.15 K with the negative values for changes in enthalpy <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13399_2025_6610_Article_IEq1.gif" Format="GIF" Height="23" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">$\left(\Delta {H}^{^\circ }\right)$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close=")" open="("> <mi mathvariant="normal">Δ</mi> <mmultiscripts> <mrow> <mi>H</mi> </mrow> <mrow /> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </mmultiscripts> </mfenced> </math></EquationSource> </InlineEquation>, entropy <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13399_2025_6610_Article_IEq2.gif" Format="GIF" Height="23" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">$\left(\Delta {S}^{^\circ }\right)$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close=")" open="("> <mi mathvariant="normal">Δ</mi> <mmultiscripts> <mrow> <mi>S</mi> </mrow> <mrow /> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </mmultiscripts> </mfenced> </math></EquationSource> </InlineEquation>, and Gibb’s free energy <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13399_2025_6610_Article_IEq3.gif" Format="GIF" Height="23" Rendition="HTML" Resolution="72" Type="Linedraw" Width="50" /> </InlineMediaObject> <EquationSource Format="TEX">$\left(\Delta {G}^{^\circ }\right)$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close=")" open="("> <mi mathvariant="normal">Δ</mi> <mmultiscripts> <mrow> <mi>G</mi> </mrow> <mrow /> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </mmultiscripts> </mfenced> </math></EquationSource> </InlineEquation>, indicating the exothermic nature of the adsorption, reduction in the randomness at the adsorbent–adsorbate interface during adsorption of methyl orange dye by Lemna minor biomass and spontaneity and feasibility of methyl orange adsorption onto Lemna minor biomass due to the reduction in Gibb’s free energy with the raise in temperature. Ecotoxicity study carried out with Eudrilus eugineae, adopting in vitro and in silico analysis revealed that the adsorbed dye by the biomass has not exhibited any toxic effect. LC50 was determined using Probit analysis, showing that the untreated methyl orange recorded 50% mortality at LC50 30.5 mg when compared to Lemna minor adsorbed biomass with LC50 90.5 mg, suggesting that the adsorbed biomass required 90.5 mg concentration to bring about 50% of the mortality, due to complete adsorption of methyl orange by the biomass. The present study implies that the processed biomass can be effectively utilized as an effective, eco–friendly adsorbent for the removal of toxic pollutants. Graphical Abstract

Effectiveness of pre-treated Lemna minor biomass in removing methyl orange dye from aqueous solutions: adsorption efficacy, kinetics, and ecotoxicity analysis

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发表日期：

2025年2月7日

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G. P. Avinash,
S. Karthick Raja Namasivayam,
P. Prakash,
S. Krithika Shree

摘要

Dyes which are used in textile and leather industries, commercial goods, and laboratories play a crucial role in accumulating lethal components in the water bodies, thereby affecting the environment. Though various physicochemical methods have been adopted for eradication of dyes, adsorption using biomass has gained more attention due to their high efficacy of removal in an eco-friendly manner. This investigation aims to analyze the effectiveness of pre-treated Lemna minor biomass in removing methyl orange dye in aqueous solution. Additionally, the study explores the ecotoxicity of the acid–alkali-treated Lemna minor biomass using an earthworm model. Collected biomass was pretreated by acid–alkali treatment which brought about characteristic changes in the structural and functional properties of biomass. Batch adsorption experiments demonstrated that the pretreated biomass effectively adsorbed the dye, with the adsorption rate significantly affected by factors such as dosage, pH, and temperature. Optimum adsorption was recorded at 500 mg of adsorbent, pH 7 and 40 °C temperature. Among the various isotherm models, Langmuir isotherm is the best fitting isotherm model. Thermodynamic studies were evaluated from 303.15 to 323.15 K with the negative values for changes in enthalpy $\left(\Delta {H}^{^\circ }\right)$ $(Δ, H^{^{\circ}})$ , entropy $\left(\Delta {S}^{^\circ }\right)$ $(Δ, S^{^{\circ}})$ , and Gibb’s free energy $\left(\Delta {G}^{^\circ }\right)$ $(Δ, G^{^{\circ}})$ , indicating the exothermic nature of the adsorption, reduction in the randomness at the adsorbent–adsorbate interface during adsorption of methyl orange dye by Lemna minor biomass and spontaneity and feasibility of methyl orange adsorption onto Lemna minor biomass due to the reduction in Gibb’s free energy with the raise in temperature. Ecotoxicity study carried out with Eudrilus eugineae, adopting in vitro and in silico analysis revealed that the adsorbed dye by the biomass has not exhibited any toxic effect. LC₅₀ was determined using Probit analysis, showing that the untreated methyl orange recorded 50% mortality at LC₅₀ 30.5 mg when compared to Lemna minor adsorbed biomass with LC₅₀ 90.5 mg, suggesting that the adsorbed biomass required 90.5 mg concentration to bring about 50% of the mortality, due to complete adsorption of methyl orange by the biomass. The present study implies that the processed biomass can be effectively utilized as an effective, eco–friendly adsorbent for the removal of toxic pollutants.

Graphical Abstract