Chemical Treatment of Textile Dyes using Chemically Modified Holarrhena antidysenterica and Citrullus colocynthis Biosorbents

Abstract

Industrial units, utilize different dyes for product coloration, employing great water usage , resulting in an enormous amount of colored wastewater production which when consumed produces a number of serious health effects affecting humanity. Hence the need of the hour is to treat colored effluents for effective dye removal. Adsorption, a simplified procedure with low operation costs, simple design and easy operation is selected. The adsorbents which are used are insensitive to toxic substances and are efficient for pollutants which have a high affinity for adsorbent surfaces, resulting in high quality of the treated effluents. Also the adsorbent is mostly regenerated, resulting in control of pollution which is a contributional step towards Green chemistry. This thesis highlights the adsorbents used for the treatment of dyes from wastewaters using adsorption process. Agricultural wastes are abundantly available in our environment and can be used as adsorbents for color removal as seen from the literature. They are abundant, cheap, simple operation and harmless byproducts are achieved. They should be treated properly prior to use in adsorption process. Many researchers have developed a number of processes for the treatment as water cleansing, passing dry air, trimming in size, char production by burning in absence of oxygen and some other precise remedy to study the long term effects of the synthetic alterations. Adsorption capacities by the data in the literature show that it is a much better method than other removal process and intensive research is being carried out to optimize this process on a commercial scale. In the present study, Holarrhena antidysenterica and Citrullus colocynthis were used for eradication of Brilliant Green (BG), Crystal Violet (CV) and Congo Red (CR) dyes which are present in waste waters and are causing serious threats towards our environment. Modification with tartaric acid was done after the adsorbents were subjected to wide variety of acidic, basic and chelating agents, with maximum dye removal for tartaric acid modified HA and CC. Acid treatment increased the surface area and raised the biosorption percentage removal. Raw and acid treated biosorbents were checked for their various biosorption criterion consisting of the dose of biosorbent, contacting period, pH studies, effects of temperature and agitation speeds, calculating their maximum adsorption percentages. Moreover removal of dyes was also assessed by isothermal studies, kinetics and thermodynamics. Linear and nonlinear adsorption isotherms were demonstrated on the isothermal data and kinetic reports for the validation. Adsorption efficiencies for the x modified adsorbents were higher than the non-modified ones. Max adsorption efficiency for HA, CC, HA-TA and CC-TA with BG was 55.12 mg/g, 50.50 mg/g, 112.3 mg/g and 79.36 mg/g. With CV dye HA, CC, HA-TA and CC-TA gave 128.21 mg/g, 136.98 mg/g, 144.92 mg/g and 166.66 mg/g and when CR dye was used the results for HA, CC, HA-TA and CC TA were 60.61 mg/g, 87.71 mg/g, 128.21 mg/g, 131.57 mg/g respectively, with the greatest dye removal with CV under all optimum conditions. A higher value of Regression coefficient (R2 ) implies the more fitting of Langmuir isotherm as displayed by all adsorbents, however when nonlinear modelling was performed, BG dye with CC was seen to follow Freundlich isotherm due to less RMSE. Also higher R2 and less RMSE prevails the dominance of Lagergren-second-order kinetics. The thermodynamics illustrates the biosorption process an exothermic, natural and feasible process. Infrared examination details acknowledged the existence of carboxyl along with hydroxyl group owing towards the electrostatic attractions among the dyes and the adsorbents. Scanning electron microscopy figures to expose the extensively coarse and porous surface area accompanying adsorbents which have been more etched and elaborated after the acidic modification to enhance the dye removal process. The oxygen-containing groups were decided by Boehm’s approach. The real waste waters containing the mixture of afore mentioned dyes were collected from Chaman Fabrics, alocal industry in Lahore and all the optimized conditions were applied on the samples, proving HA and CC as novel and excellent biosorbents for the pretreatment of the local industrial waste water. The results obtained from this study indicate the utilization of batch process for an economic and eco-friendly way for scavenging dyes from wastewaters on industrial level. Both adsorbents Holarrhena antidysenterica and Citrullus colocynthis and modifying agent tartaric acid are easily available. Hence tartaric acid modified adsorbents appears to be a good choice for the removal of BG, CV and CR dyes from industrial effluents. Key words: Holarrhena antidysenterica, Citrullus colocynthis, SEM/EDX, Langmuir Isotherm, Pseudo-second-order kinetics, Film diffusion mechanism.