Water pollution caused by textile manufacturers' incapacity to properly dispose of waste water is currently one of the world's significant issues. Textile industries contribute significantly to the world economy and pollution in several nations, including China and South African estuaries (Olisah, Adams, & Rubidge, 2021). As textile industries generate large amounts of highly colored wastewater containing a diverse range of persistent pollutants, dye-containing wastewater is a significant polluter of the environment that also affects human health (Al-Tohamy et al., 2022). Around 7.107 tons of synthetic dyes are produced globally each year, with over 10,000 tons of such dyes used by the textile industry (Chandanshive et al., 2020). Many harmful chemicals are employed in the dye manufacturing process, including dyes, surfactants, electrolytes, emulsifiers, media, starches, yeasts, and oxidants. When these chemicals are thrown improperly, they can harm nearby bacteria, fish, and aquatic creatures. These pollutants can also permeate the soil, remain there for extended periods, harm groundwater supplies, and endanger human life. Furthermore, textile-dyed wastewater is highly colored, often varies depending on the kind of dye, and has a high temperature, so it must be adequately cleaned before release to avoid environmental damage (Zhou, Lu, Zhou, & Liu, 2019).
The removal of colorants from wastewater has faced many significant disadvantages, such as high costs, hazardous product production, and high energy needs. As a result, we must seek new solutions and create more ecologically friendly technology. Because conventional adsorbents are easy to find, easily accessible, renewable, ecologically benign, and can replace traditional adsorbents, biosorption is one of the most successful ways (Mustafa T. Yagub, Sen, Afroze, & H.M.Ang, 2014). To date, a range of low-cost adsorbents, such as potato peel (Guechi & Hamdaoui, 2015), dragon fruit leaves (Haddadian, Shavandi, Abidin, Razi, & Ismail, 2013), pine cone (Sen, Afroze, & M., 2011), rice straw (Cheng et al., 2015), fly ash (Das, Barman, & Thakur, 2012), and other materials, have been investigated. Adsorbents based on these biologics have been utilized to eliminate acidic, basic, and reactive dyes from waste water. All of these bio-wastes are common and have little monetary worth. Adsorption is extremely reliant on the pHsolution, the dosage of the adsorbent, the temperature, and the concentration of other solutes present in the solution, according to the authors.
There are some studies using pine cone and pine leaves for removal of methylene blue (MB) from aqueous solution (Ertugay & Malkoc, 2014; M.T. Yagub, Sen, & Ang, 2012). Pine tree cones and leaves were cleaned multiple times with distilled water to eliminate impurities such as grit before drying for two days in an oven at 65oC. A crusher was then used to chop and grind dried pine materials. The powders were then passed through British Standard Sieves, with particles less than 100 µm collected in a plastic container for pine cones and particles less than 350 µm collected in a plastic container for pine leaves, both to be used as adsorbents. At 30°C, pine cone and pine leaf biomass had maximal monolayer adsorption capacities of 129.87 mg/g and 126.58 mg/g, respectively (M.T. Yagub et al., 2012). Fresh needles of Pinus sylvestris L. were dried at 80ºC for 48 h and cut into small pieces. Adsorption experiments were carried out 250–500 µm at adsorbent particle size (Ertugay & Malkoc, 2014). The maximum monolayer adsorption capacity of this material was found to be 101 mg/g at 45°C. FTIR spectrum result revealed the presence of adsorbing groups such as carboxyl, hydroxyl, and aromatic-CN stretching in the needles. These studies only investigated the MB adsorption capacity of pine needles but did not investigate the adsorption capacity with other organic dyes. The material used in these studies is unmodified pine needles and the mechanism of MB adsorption in water has not been specified.
Pinus kesiya is popular in Southeast Asia for a range of applications such as boxes, pulp and paper, and temporary utility poles. Scientists have paid little attention to Pinus kesiya as an adsorbent to eliminate methylene blue and methyl orange from aqueous solutions, even though it is a cheap, easy-to-use, and ecologically benign material. In this study, we explore the MO and MB adsorption capability of heat-treated pine needles at 300oC. The influence of critical adsorption factors on the adsorption efficiency was investigated. Isothermal, kinetic, and thermodynamic analyzes, as well as biomass properties before and after adsorption, were used to indicate the mechanism of dye adsorption of this material.