Recycling of Labada (Rumex) biowaste as a value‐added biosorbent for rhodamine B (Rd‐B) wastewater treatment: biosorption study with experimental design optimisation

Abstract

Rhodamine B (Rd-B) is a highly toxic dye causing serious environmental and health issues. This study focussed on the development of a cost-effective and ecologically friendly remediation technique utilising Labada (Rumex), a readily available agricultural biowaste. Experimental design was applied for the first time to establish the parametric effects on the rhodamine B (Rd-B) biosorption and to optimise the process for the highest rhodamine B (Rd-B) removal. At the optimised conditions of 25 °C, 500 mg L−1 concentration, natural solution pH of 5.5–6.0, and 1 g L−1 dosage; the maximum biosorption capacity was 0.219 mol kg−1. Using the results of physicochemical characterisation and rhodamine B (Rd-B) adsorption measure- ments, isotherm and kinetic models were made to predict performance towards rhodamine B (Rd-B) removal from water reliably. The rhodamine B (Rd-B) biosorption kinetic was best correlated to the pseudo-second-order, while the equilibrium to the Freundlich isotherm. These isotherm and kinetic models can be used to quickly screen among larger sets of possible adsorbents and guide the development of novel, highly efficient adsorbents for rhodamine B (Rd-B) removal from water. Characterisation of Labada (Rumex) was accomplished by scanning electron microscope (SEM–EDX), energy dispersive X-ray, Fourier transform infrared, and thermogravimetric analyses. Regeneration of exhausted Labada (Rumex) biosorbent was best performed using 50% hydrochloric acid. This study highlights the strong feasibility of Labada (Rumex) biosorption as a green and effective technique for Rd-B removal.