Biochar, produced from brown seaweed Turbinaria conoides through microwave assisted pyrolysis, was employed as a sorbent for the remediation of Remazol brilliant blue R (RBB). Pyrolysis experiments were conducted at different processing conditions and the resulting products of microwave pyrolysis (biochar, bio-oil, and gas) at each condition were quantified. The optimum yield of 27.3 wt% for the biochar was achieved by applying pyrolysis conditions including power of 280 W and feedstock ratio of 10:4 as seaweed: activated carbon. The biochar was characterized using Fourier transform infrared spectroscopy, energy dispersive X-ray analysis and scanning electron microscope. The results indicated that pyrolysis increased roughness and number of pores on the biochar surface thereby enhanced the sorption potential of seaweed. Adsorption experiments revealed that optimum RBB biosorption occurred at pH 2 for seaweed-derived biochar with maximum RBB sorption capacity of 85.3 mg/g. Application of different isotherm models (Freundlich, Langmuir, and Toth) indicated that the three-parameter Toth model resulted in improved prediction of isotherm data with less % error, high correlation coefficient, less chi-square and root mean square error values. The experimental kinetics data analyzed using different models highlighted that the pseudo-second order kinetic model produced superior description of the experimental data. The elution experiments carried out using various elutants (0.1 M HNO3, HCl, H2SO4, NaOH, Na2CO3, and EDTA) indicated that NaOH performed better in releasing RBB from dye-bounded biochar with elution efficiency of 99.5%. The regenerated biochar sample was restored and successfully employed for three sorption-elution cycles. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13143, 2019. © 2019 American Institute of Chemical Engineers