## 1 Introduction  
With the progress of human life and the escalating anthropogenic activities, pollution of water has become a crucial environmental concern. Various contaminants are intimidating the aquatic system. These contaminants include, but not limited to, drugs and pharmaceuticals, heavy metals and anions, plastics and polymers, dyes and pigments, and pesticides [1]. Industries, particularly, textiles, leather, food, and cosmetics encompass using dyes with diverse chemical structures. Consequently, the discharge of these industries is basically 'huge' amounts of intensively colored wastewaters. Release of such an effluent into the receiving water bodies causes a direct mutilation of water quality in terms of the aesthetic properties (color, pH, salinity, total organic carbon (TOC), suspended solids, etc.). Such a change negatively impacts the ecosystem. Just thinking about the capability to restrain the photosynthetic ability of water plants and microorganisms, shows the magnitude of the problem. This effect is worsened by the diverse structure of these dyes and their resistance to biodegradation. The negative impact does only involve the environment but also extends to human health with reported carcinogenic activity [2; 3; 4; 5]. Basic fuchsin (BF), also known as Basic Violet 14, is chemically recognized as benzenamine, 4-[(4-aminophenyl) (4-imino-2,5-cyclohexadien-1-ylidene) methyl]-2-methyl hydrochloride, Figure 1. BF is a mixture of dyes (rosaniline, pararosaniline, new fuchsine, and Magenta II) that is commonly used in gram-staining and in a mixture with phenol for acid-fast staining of mycobacterium (tuberculosis and leprosy) in the procedure known as Ziehl-Neelsen [6; 7]. Moreover, BF is widely used in textile and leather industries. Yet, the safety data sheet of BF shows that the dye is inflammable and might cause skin and eye irritations. Moreover, the ingestion of BF might cause internal organs' impairment and repeated exposure is usually associated with nervous system damage with different symptoms [8; 9; 10]. Keeping in mind these toxic effects and the associated changes in the eco-system, the inevitability for dyes' removal and decolorization of water becomes evident. A literature survey shows that several approaches have been reported for the removal of dyes from aquatic bodies. However, insofar as BF removal is concerned, only a few trials were reported in the literature [10; 11; 12; 13]. Reported techniques were mainly based on adsorption (either physisorption or chemisorption) of target dyes on an adsorbent recycled from agricultural/animal waste products [14; 15; 16; 17; 18]. A common feature among all the adopted trials is the intimate attempts to develop the model or the ideal adsorbent. Such an adsorbent must have particular criteria such as availability at low-cost and without extensive preceding treatment, liability for regeneration, the possibility for application on a large scale, and be green or in other words does not further contaminate the environment or produce a toxic sludge [19; 20; 21; 22; 23; 24]. Activated carbons are promising adsorbents, yet, being expensive and with an inability to be revitalized they confine their applications on the large scale [25]. Yet, developing such an adsorbent from a natural source such as recycled agricultural/animal wastes ensures to a high extent the availability of these criteria. Pistachio nutshells (PNS) are a by-product of pistachios; one of the most known nut trees worldwide that belongs to the cashew family (Anacardiaceae) [26]. As a desert plant, pistachio can tolerate harsh conditions of temperature and salinity but not humidity. The tree origin is mainly Asia (central and western) with Iran being the top producer [26; 27]. As is known, pistachio is commonly used as a snack (fresh or roasted) as well as being an ingredient of deserts, ice-creams, sauces, pastes, and butters. Pistachio shells are usually thrown away after eating the kernel with no further use and their fate is either incineration or dumping.