Invasive weed transformed into eco-friendly sponge for industrial dye pollution

Researchers have developed an effective, low-cost adsorbent for removing industrial dye from wastewater by using an unlikely source: the notorious invasive plant, Lantana camara. A team from Nalanda University, Nagaland University, and China Agricultural University, among other institutions, successfully converted both the leaves and stems of this widespread weed into biochar, a charcoal-like substance with powerful adsorption properties. This innovative approach tackles two significant environmental challenges simultaneously—the management of an aggressive invasive species and the purification of water contaminated with toxic dyes like methylene blue.

From Noxious Plant to Powerful Purifier

The process involved collecting Lantana camara plants, separating them into leaves and stems, and then heating the dried biomass at 600 °C in a process called pyrolysis. This converted the plant material into two types of biochar, one from the leaves (BCL600) and one from the stems (BCS600). The scientific team, led by Deepa Kundu and Prabhakar Sharma, conducted a thorough characterization of these materials using advanced techniques like scanning electron microscopy and infrared spectroscopy. Their analysis confirmed the porous, carbon-rich nature of the biochar and identified various functional groups on its surface that are essential for capturing pollutant molecules from water.

Decoding the Adsorption Dynamics

In a series of batch experiments, the biochar demonstrated a remarkable ability to remove methylene blue from aqueous solutions. The efficiency of the process was highly dependent on the solution's pH, with dye removal increasing significantly in more alkaline conditions. This is attributed to favorable electrostatic interactions between the negatively charged biochar surface and the positively charged dye molecules at higher pH levels. The investigation also found that the leaf-derived biochar possessed a higher maximum adsorption capacity compared to the stem-derived biochar, though both proved effective. The adsorption kinetics followed a pseudo-second-order model, suggesting that the capture of dye molecules is a complex, multi-step process involving both surface attachment and diffusion into the biochar's pores.

A Spontaneous and Favorable Reaction

A thermodynamic analysis of the adsorption process revealed that the reaction was both spontaneous and exothermic. This indicates that the removal of methylene blue by the Lantana biochar occurs naturally without the need for external energy input and is more favorable at lower temperatures. The primary mechanisms driving the adsorption were identified as a combination of electrostatic attraction, hydrogen bonding, and n-π and π-π interactions, where the aromatic structures of the dye molecules bind to the carbon-based surface of the biochar. These findings confirm that Lantana-derived biochar is a potent and effective bio-sorbent for treating industrial effluent.

Prabhakar Sharma, the corresponding author from Nagaland University, commented on the broader implications of the work. "Our findings present a sustainable pathway for what is often called 'waste valorization.' We have taken a problematic invasive plant that threatens biodiversity and transformed its entire biomass into a valuable tool for environmental remediation. This not only provides a cost-effective solution for wastewater treatment but also offers a tangible strategy for managing the spread of Lantana camara, turning an ecological threat into an environmental asset."

While the current results are promising, the research was conducted under controlled laboratory conditions using a single type of dye. The next phase of this work could involve testing the biochar's performance on real-world industrial wastewater, which contains a complex mixture of different contaminants. Further research may also explore modifying the biochar's surface to enhance its selectivity and capacity for capturing a wider range of pollutants, including heavy metals and other organic compounds. This foundational work opens the door for the practical application of invasive plant biomass in large-scale water purification systems.

Corresponding Author: Prabhakar Sharma

Original Source: https://doi.org/10.1007/s44246-024-00108-1

Contributions: Deepa Kundu: Conceptualization, experiments, writing first draft. Prabhakar Sharma: Conceptualization, supervision, writing, editing, reviewing. Sayan Bhattacharya: Writing, review and editing. Kaushik Gupta: Writing –review and editing, developing diagrams. Shubhalakshmi Sengupta: SEM image analysis, review and editing. Jianying Shang: Review and editing.