Adsorption of Crystal Violet from aqueous solution onto eco-friendly native Carpobrotus edulis plant

Abstract

The recent interest in the adsorption of pollutants on biomaterials has been gaining widespread attention, especially in the utilization of natural materials of vegetable origin-based composite biomaterials. In this study, the equilibrium and the kinetics of Crystal Violet adsorption onto native Carpobrotus edulis Mediterranean plant, which is biodegradable and less expensive, was investigated. Experiments were carried out as a function of adsorbent dose (0.08–1 g), contact time initial (5–180 min), ionic strength of salt NaCl (0.05–0.5 M), and solution pH (2–12). pH and ionic strength do not have a major influence on the adsorption of Crystal Violet on the biomaterial studied. The adsorption process followed a kinetic model of the pseudo-second-order. These results suggest that the native Carpobrotus edulis plant could potentially be used as an environmentally friendly adsorbent for eliminating cationic dyes from aqueous solutions.

Introduction

The main source of dye wastewater is textile, leather, pulp, rubber, plastics, cosmetics, pharmaceutical, and food industries. Because dye wastewater always comes as large quantities, complex composition, depth of color, and is highly toxic, it causes severe environmental pollution and hazards to human health if it is not properly treated before discharging into natural water [1], [2], [3]. Current techniques for treating dye wastewater includes physical, chemical, and biological processes, and so on adsorption [4], [5], chemical coagulation, separation of the liquid membrane, electrolysis, biological procedures, oxidation, and other processes have been studied in different removal methods [6]. These processes vary in their effectiveness, cost, and environmental impact [7]. However, the adsorption process is much more efficient among these processes than other processes because of its ready availability, lower cost, and wider application range. The hunt for adsorbents that meet water treatment industry requirements and standards and are also environmentally friendly, highly effective, low cost, and available in tonnage quantities [8], [9] is of vital importance.

Crystal Violet, also known as genetic violet, is a triaryl-methane dye, widely used as a violet dye for cotton and silk dyeing in textile industries. It also finds application in paint and printing inks [10], [11], [12]. It is used as a biological stain within the medical profession and is the active ingredient in Gram's stain. It is used as a bacteriostatic agent in animal and veterinary medicine. The dye can also be used in humans as a disinfectant for the exterior skin. It is used as an additive to poultry feed to inhibit mold, intestinal parasites, and fungal propagation [13], [14]. Crystal Violet is a protein–dye and is thus used as a bloody fingerprint additive. Crystal Violet is carcinogenic and has been identified as a recalcitrant molecule because it is poorly metabolized by microbes is non-biodegradable, and may persist in a variety of environments. The dye can cause moderate eye irritation, which brings light to painful sensitization. This can also cause permanent corneal and conjunctive damage because the drug includes a cationic dye. It is extremely poisonous to mammalian cells and can cause skin irritation and digestive tract irritation if absorbed in harmful amounts through the skin. It can also cause respiratory and renal failure in extreme situations [15], [16], [17], [18].

Natural materials of vegetable origin offer several advantages; they are biodegradable, non-toxic, low-cost, and contain in their structure several functional groups that can create bonds and fix polluting entities. The selection of Carpobrotus edulis plant is based on their relative abundance in different areas of Morocco and their adsorbent capacity to various organic and inorganic pollutants. [19], [20].

The aim of this study was therefore to explore the potential of the native Carpobrotus edulis plant as a low-cost adsorbent to remove Crystal Violet from aqueous solutions using the batch equilibration technique. The effects on Crystal Violet adsorption rates of the adsorbent dose, contact time, ionic strength, and solution pH were investigated. The adsorption kinetics was also evaluated and reported.