In the present research, an efficient, eco-friendly method of utilization of coal fly ash in the form of zeolite, to treat wastewater containing dyes has been studied. Response surface methodology involving Box-Behnken design was applied for a batch process to evaluate the effect of process parameters like contact time, dye concentration, agitation speed, pH and adsorbent dosage onto zeolite. Disperse Orange 25 (DO) dye showed maximum 96% removal under optimal conditions of contact time (119 min), dye concentration (38.00 mg/L), agitation speed (158 rpm), pH (6.10) and adsorbent dosage (0.67 g/L), whereas 95.23% of Disperse Blue 79:1 (DB) dye removal was observed at adsorbent dose (1.05 g/L), dye concentration (26.72 mg/L), agitation speed (145 rpm), pH (5.68) and contact time (122 min). Study concluded that cenospheres derivatized zeolite adsorbent is efficient, eco-friendly and economical along with high potential for removal of DO and DB dyes from the aqueous solutions.

In the present study, a series of bioceramic capped manganese doped superparamagnetic iron oxide (SPIONs) nanoparticles (mHAP NPs) were synthesized by one pot in situ reduction. The aging of the bioceramic on the SPIONs was optimized to achieve variation in functionality, morphology, magnetic susceptibility, shape and size of the NPs and ultimately remediation effectiveness of arsenite; As(III).Results indicate that among various synthesized NPs, the 6 h aged mHAP NPs with 27 emu magnetic susceptibility, 57.30 m 2 g À1 surface area and 75.64Å average pore diameter offer the best option as an adsorbent for posthaste removal of As(III) from synthetically spiked water. Further, predictive modeling using response surface based Central Composite Design (CCD) was applied to achieve and optimize process parameters for the removal of As(III) by mHAP NPs keeping variable operational parameters to a minimum in batch experiments. The individual and collective effect of four process parameters, i.e. pH, mHAP NP dose, contact time and initial As(III) concentration on As(III) adsorption were studied. The results from statistical design signify that, with 0.2 g L À1 of above mHAP NPs adsorbent dose, 98% As(III) (initial concentration 0.1-0.4 mg L À1 ) removal was possible in 210 min at pH 6.5 which is well within the prescribed value as per WHO guidelines. The adsorption process of As(III) onto mHAP NPs showed excellent correlation with a Langmuir isotherm with a maximum adsorption capacity of 12.0 mg g À1 .Kinetic and thermodynamic studies reveal pseudo-second-order kinetics with an exothermic and spontaneous adsorption of As(III) on the synthesized adsorbent. Cyclic regeneration of mHAP NPs indicated positive impact in remediation technology at low production cost. Fig. 6 3-D response surface plots of the effects of (A) pH, (B) mHAP NPs dose, and (C) initial As(III) concentration with contact time, (D) mHAP NPs dose, and (E) As(III) concentration with pH (F) initial As(III) concentration with mHAP NPs dose and (G) cumulative effect of all variable parameters. 32872 | RSC Adv., 2017, 7, 32866-32876 This journal is