Methylenblaulösung 0,5 in Wasser

Faba bean hulls,  Vicia faba (FBP), are investigated as biosorbents for the removal of methylene blue (MB) dye from aqueous solutions by a novel and efficient sorption method using ultrasonically-assisted (US) shaking. Ultrasonics remarkably improved the sorption rate compared to conventional (CV) shaking while maintaining the same sorption capacity. The ultrasonic sorption rate was four times higher than its conventional counterpart at 3.6 mg/l initial dye concentration, 5 g/l adsorbent dose and pH 5.8. 

Under the same adsorbent dose and pH conditions, the percent removal ranged from 70-80% in the low dye concentration range (3.6-25 mg/L) and reached about 90% at 50 mg/L of the initial dye concentration. According to the Langmuir model, the maximum sorption capacity was estimated at 140 mg/g. A multiple linear regression statistical model showed that adsorption was significantly affected by initial concentration, adsorbent dose, and time. FBP could be successfully used as a low-cost biosorbent for the removal of MB from wastewater using US biosorption as an alternative to CV sorption. US biosorption delivers the same sorption capacities as CV biosorption, but with a significant reduction in operating times.

Significant amounts of synthetic colorants are used in many process industries. The textile, pharmaceutical, leather, food processing, cosmetics and paint industries emit about 10-15% of over 0.8 million tons of different types of dyes produced annually worldwide. The dye business is forecast to grow at around 2-3% annually due to the increasing global production and consumption of dyes. In developing countries like India and China, the rate of production of dyes is steadily increasing every year. Without proper treatment, these dyes harm the environment, marine life and pose a serious health threat to humans, especially when degraded, becoming toxic, recalcitrant, mutagenic and carcinogenic.

• Methylene blue (MB) (3,7-bis(dimethylamino)-phenothiazin-5-ium chloride) is a cationic thiazine dye commonly used in biological dyeing, paper, hair, cotton and wool dyeing  ⁴  . 
• In addition, MB injection is used to treat methemoglobinemia and urinary tract infections. However, the accumulation of MB in wastewater has adverse health effects such as breathing difficulties, vomiting, burning eyes, diarrhea and nausea.
• Several physicochemical and biological processes have been successfully applied to treat dye effluents  ⁶  , examples being membrane filtration  ⁷  , photocatalytic degradation  ⁸  , irradiation  ⁹  , biological treatment  ¹⁰  , conventional adsorption  ¹¹  and ultrasonically assisted adsorption  ¹²  .
• Adsorption is a commonly used strategy because of its relative ease of operation, the availability of its adsorbents, its selectivity, and its potential for scale-up. Among the adsorbents used, activated carbon is often used because of its efficiency and large surface area  ¹³ . However, it has significant limitations due to its high regeneration costs and environmental impact
• . The performance of the adsorption process could be improved by ultrasonics. The ultrasonic process creates waves that enhance and accelerate mass transfer by creating shear forces in the solution via microstreams, microturbulence, sonic waves and microjets without significantly altering the balance of the adsorption/desorption system. ^{This in turn could}  accelerate adsorption 14 , 15 .

For reasons of environmental sustainability and economic reasons, many researchers investigated biosorption as an inexpensive, safe, and potentially effective alternative to traditional sorption; especially for the removal of heavy metals and dyes from waste water. 

Several studies reported MB removal with untreated biosorbents or those thermally treated and/or activated with acids or bases. In studies using untreated biosorbents, some of the highest reported maximum adsorption capacities (18–333 mg/g) were related to cellulosic and lignin-based adsorbents such as chitin  , rice straw  lignin ²⁰  , cherry wood  ¹⁴  , wheat  hull ²¹ , and banana, orange, and pineapple fruit  hulls ²²  in addition to biomass such as  Aspergillus fumigatus   and  Bacillus subtilis  ²⁴  and others such as fly ash geopolymer  ²⁵  , white pine sawdust ¹⁸  and  Abelmoschus esculentus  seeds  ²⁶  . Regarding the pretreated adsorbents, some of the highest maximum adsorption capacities (20-672 mg/g) have been reported for nitric acid treated walnut wood activated carbon  ²⁷  , NaOH modified spent tea  ²⁸  , sulfuric acid activated cotton stalks  ²⁹  . Base-activated bamboo charcoal  ³⁰ , HCl-activated oil palm  fiber ³¹  , and coconut shell activated charcoal modified by KOH at 816°C  ³²  , in addition to pretreated peels such as oven-dried peels of  Artocarpus camansi  ³³  , banana peels activated with NaOH  ³⁴  , modified jackfruit peel with microwave-induced NaOH activation, and grapefruit skin activated by NaOH using microwave heating .

Broad beans (  Vicia faba  ) are heavily consumed in different parts of the world such as Mediterranean Europe and Africa, Latin America, China and India hence large amounts of the pods are discarded as waste. Only part of this waste is used by farmers as animal feed. In a previous study, fava bean powder was used to remove heavy metal ions from Pb(II), Cd(II), and Zn(II)  ³⁷  to achieve removal efficiencies of 100%, 92.86%, and 36.86%, respectively. On the other hand, broad bean hulls were used to remove MB dye with a maximum adsorption capacity of 192.7 mg g  ⁻¹  at 30 °C  ³⁸ .

The aim of the present study is to develop a viable and efficient biosorption process for the removal of MB dye from aqueous solutions using broad bean pods (FBP) as an inexpensive adsorbent. For this purpose, biosorption was performed using ultrasonically-assisted (US) shaking as an alternative to conventional (CV) magnetic stirring. Sorption performance in terms of capacity and rate was evaluated and compared to CV biosorption under various conditions including adsorbent dosage, initial dye concentration, pH and contact time. To determine the influencing operating parameters, a statistical multiple linear regression model was developed using the reverse method on the R program.