Enhanced Wastewater Remediation Using Mesoporous Activated Wheat Straw Biochars: A Dye Removal Perspective

Abstract

The escalating contamination of water bodies by synthetic dyes necessitates innovative and ecoconscious strategies for wastewater treatment. In this study, activated biochars BC-800 (1:0.25), BC-800 (1:0.5), and BC-800 (1:1) from wheat straw were synthesized. Here, ratios denote the mass relationship between wheat straw and potassium hydroxide; "800" represents the pyrolysis temperature. These activated biochars were rigorously characterized revealing the most efficient material, BC-800 (1:1), presenting a surface area of 2578.82 m 2 /g and average pore diameter of 5.51 nm. Across parallel batch experiments, it effectively extracted synthetic dyes (rhodamine B (RhB), methylene blue (MB), and methyl orange (MO)) from wastewater within 15−20 min, primarily through chemisorption pathways. Increased surface area and porosity resulted in a greater dispersion of adsorption sites including C�C linkages (π−π interactions) and Hbonding via surface carbonyl groups (C�O). To understand the adsorption mechanism, Langmuir, Freundlich, and Temkin isotherm models were employed to investigate the equilibrium adsorption behavior. Results show that BC-800 (1:1) followed the Freundlich isotherm (R 2 : 0.9659 for RhB, 0.9927 for MB, and 0.9979 for MO, respectively), showing dye molecules form multilayers on the surface of the biochar (π-stacking). Biochar recycling through chemical regeneration demonstrated sustained dye removal efficiency >90% for BC-800 (1:1) over multiple cycles.

Lignin Smart Nanoparticles for Effective and Eco-Friendly Resource Recovery from Wastewater: Status, Challenges, and Opportunities

“…Similarly, from Table , we observe that adsorption, membrane separation, and precipitation are very common removal/recovery techniques across the various pollutants/resources, particularly among ubiquitous substances such as nutrients and minerals (Figure ). This observation supports the central theme of this perspective, which is to exploit [bio]­polymers for the purpose of resource recovery from wastewaters, as there is plenty of research demonstrating the effectivity of polymers in adsorption, membrane separation, and precipitation processes. − For adsorption and filtration processes, in particular, characteristics such as the porosity, specific surface area, pore volume, and surface charge of the material significantly control the removal/recovery efficacy, and as such, in this perspective, we focus on the use of polymers as nano- and microstructures where these important characteristics are enhanced . Specifically, adsorption is a clean, low-cost, selective, and effective process. , The characteristics of an effective adsorbent are high adsorption capacity, thermal stability, efficiency, reuse, and recycle capability. , From these perspectives, activated carbon, which is the primary adsorbent used at an industrial scale, suffers majorly from high costs, and poor affinity to hydrophilic resources such as anionic dyes, and lignin nano- and microparticles being amphiphilic, are potential competitive adsorbents.…”

“…Dyes (for which textiles are the major contributors) and pharmaceuticals present in wastewater constitute a threat to all living organisms and the environment. ,, Moreover, their recuperation from wastewater could be economically beneficial . Particularly, dyes in water bodies and in soil may impede photosynthesis, bioaccumulate, and impair living organisms .…”

“…An imminent transition from fossilized to renewable feedstocks to produce sustainable energy, fuels, commodity chemicals and advanced materials is needed to mitigate climate change, environmental contamination, and support the rapid population growth around the globe. , Wastewater, composed of 1% dissolved and suspended solids, and 99% water has been recently regarded as a mine of valuable resources, − with approximately 380 trillion L/year of wastewater produced globally, ∼16 times the volume emissions of CO 2 from fossil fuels and industry worldwide in 2022 . This diverse, unsteady, and heterogeneous resource may contain microorganisms (e.g., infectious bacteria, viruses, protozoa, and helminths), minerals (e.g., Ca, Mn, and Mg) , nutrients (e.g., P, N, and K), metals (e.g., Cu, Co, Cr, and Zn), dyes, pharmaceuticals, per- and polyfluorinated substances (PFAS), and energy, among others. ,− Exploiting this reservoir may not only increase access to potable water, decrease the concentration of contaminants discharged into water bodies, and minimize pollution that results in problems such as eutrophication but also establish a route for the sustainable circularity of resources, thus improving the overall economic and ecological profitability in wastewater plants and, particularly, supporting the worldwide net-zero greenhouse gas emissions target projected to be reached between 2050 and 2080s. ,− …”

“…Of the technologies being researched, electrochemical, biologically activated membranes, and adsorption systems stand out. , Recent reports have demonstrated the efficacy of nanomaterials to extract dyes, and low-, medium-, and high-toxicity metals from wastewater via accessible and low-cost adsorption processes. ,, The precursors for these nanomaterials are predominantly carbon-based (e.g., graphene, carbon nanotubes, membranes, and activated carbon), metal oxide-based (e.g., MgO, CdO, Fe 3 O 4 ), silica-based (e.g., silica nanoparticles), and to a lesser extent polymer-based (e.g., nanomaterials, and aerogels). ,, Polymer-based, specifically biopolymers, could significantly enhance advanced adsorption processes technically, socio-economically, and environmentally. In fact, lignin, one the major constituents of lignocellulosic biomass (nonedible) represents the second-most abundant biopolymer after cellulose (∼40%, w/w cellulose, and ∼25% w/w lignin of lignocellulosic biomass); it is a renewable reserve of aromatic compounds, accounting for about 30% of the total nonfossil carbon on Earth, with carbon representing about 60% of the structure of lignin, , as polymer chains and nanoparticles are efficacious at removing various contaminants from wastewater, including metals, dyes, pharmaceuticals, and nutrients, making it a potential efficacious adsorbent for resource recovery from wastewater. ,− Although nano- and microstructured lignin particles are highly attractive adsorption materials, their industrial valorization is hampered by the heterogeneity of the polymer.…”