## 1 Introduction
As per the Food and Agriculture Organization (FAO) reports, around \(30\times 10^{6}\) tons of PNS are dumped annually, an issue that negatively impacts the environment [28]. Therefore, it is quite interesting to explore PNS as an adsorbent for the remediation of wastewater from dyes. Since the objective of the current approach is to develop a model adsorbent, variables affecting the adsorption process (pH, adsorbent dose (AD), dye concentration (DC), and stirring time (ST)) have been optimized through a novel methodology, definitive screening design (DSD) [29]. This design and to the best of our knowledge, has not been explored before for optimizing the adsorption process. Moreover, most of the reported techniques that employ pistachios' by-products (hull, shells, etc.) as adsorbents are using the conventional methodology; one-variable-at-a-time (OVAT), for studying the adsorption process [30; 31; 32; 33; 34]. Table 1 summarizes most of the efforts that used pistachios by-products as an adsorbent. Moreover, it shows also some of the methods reported in literature for removing BF [10; 11]. Figure 1: Chemical structure of basic fuchsin (BF). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Adsorbent** & **Modification Method** & **Analytical Approach Used** & **Surface Area** & **Adsorbate** & **Adsorption** & **\% Removal** & **Ref. ** \\ \hline Raw Pistachio & \multirow{2}{*}{Please see the experimental section of the} & Multivariate & \multirow{2}{*}{4.24} & \multirow{2}{*}{BF} & \multirow{2}{*}{118.2} & \multirow{2}{*}{99.71\%} & Current \\ Nutshells (RPNS) & current approach & analysis—DSD & & & & \\ \hline Pistachio shell & \multirow{2}{*}{Pistachio shell was washed several times, and dried at 70 °C. The dried biomass was then grounded and used.} & One-variable at a & \multirow{2}{*}{ND} & CL Reactive & \multirow{2}{*}{109.35} & \multirow{2}{*}{ND} & [30] \\ \hline Pistachio hull & Raw hull waste was used following air-drying for three & \multirow{2}{*}{OVAT} & \multirow{2}{*}{1.04} & \multirow{2}{*}{Cr(VT)} & \multirow{2}{*}{116.3} & \multirow{2}{*}{99\%} & [31] \\ powder (PHP) & days, crushed, powdered, and then sieved. & & & & & \\ \hline Pistachio hull & Raw hull waste was used following air-drying for three & \multirow{2}{*}{OVAT} & \multirow{2}{*}{1.04} & Methylene & \multirow{2}{*}{602} & \multirow{2}{*}{99.7\%} & [32] \\ powder (PHP) & days, crushed, powdered, and then sieved. & & & & & \\ \hline Pistachio shells were washed, dried at 80 °C, and then & \multirow{2}{*}{OVAT} & \multirow{2}{*}{814.23} & \multirow{2}{*}{Pb(II)} & \multirow{2}{*}{24.0} & \multirow{2}{*}{82.9\%} & [33] \\ Carbon (PSC) & carbon was grounded, sieved, washed, and then dried for further use. & & & & \\ \hline Pistachio nutshell & \multirow{2}{*}{Pistachio nutshell char was soaked in potassium} & \multirow{2}{*}{OVAT} & \multirow{2}{*}{ND} & Methylene & \multirow{2}{*}{296.57} & \multirow{2}{*}{ND} & [34] \\ activated carbon & hydroxide (KOH) with the ration of (char: KOH) 1: 1.75 & & & & & \\ (PSAC)-microwave (wt \%). The activation step was done in a glass reactor assisted KOH activation & inside a modified microwave oven with a power of 600 & & & & \\ activation & mV and for 7 min. & & & & \\ \hline \multirow{4}{*}{- Bottom ash} & \multirow{4}{*}{H\({}_{2}\)O\({}_{2}\) for 24 h. The product obtained was kept in an oven at 100 °C. Bottom ash was further activated in a furnace at 500 °C for 15 min. in presence of air.} & \multirow{4}{*}{ND} & \multirow{4}{*}{ND} & \multirow{4}{*}{98–94.25\%} & [10] \\  & & & & & & \\ \hline \multirow{4}{*}{Calcined Mussel (CMS)} & Massel builds were collected, washed, dried at 378 K for 12 h, powdered, and then calcined at 1173 K for 2 h, & & & & \\ \cline{1-1} \cline{2-6} \cline{1-1}  
Application of such a design; (DSD), guarantees the preservation of method greenness where the lowest amount of resources (chemicals, energy, efforts, etc.) are utilized. Moreover, the obtained data can be treated with a high degree of inevitability.