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Biochar adsorbents synthesized from food and agricultural wastes are commonly applied to eliminate heavy metal (HM) ions from wastewater. However, biochar's diverse characteristics and varied experimental conditions make the accurate estimation of their adsorption capacity (q e ) challenging. Herein, various machine-learning (ML) and three deep learning (DL) models were built using 1518 data points to predict the q e of HM on various biochars. The recursive feature elimination technique with 28 inputs suggested that 14 inputs were significant for model building. FT-transformer with the highest test R 2 (0.98) and lowest root mean square error (RMSE) (0.296) and mean absolute error (MAE) (0.145) outperformed various ML and DL models. The SHAP feature importance analysis of the FT-transformer model predicted that the adsorption conditions (72.12%) were more important than the pyrolysis conditions (25.73%), elemental composition (1.39%), and biochar's physical properties (0.73%). The two-feature SHAP analysis proposed the optimized process conditions including adsorbent loading of 0.25 g, initial concentration of 12 mg/L, and solution pH of 9 using phosphoric-acid pre-treated biochar synthesized from banana-peel with a higher O/C ratio. The t-SNE technique was applied to transform the 14-input matrix of the FT-Transformer into two-dimensional data. Finally, we outlined the study's environmental implications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Declaration of competing interests None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this study, the feasibility of Mg/Al layered double hydroxides (LDH) functionalized coffee ground waste biochars (LDH MgAl @CWGB) as a potential adsorbent to selectively recover phosphate (PO 4 3- ) and nitrate (NO 3 - ) ions in aqueous phases and their consecutive uses as a slow-release fertilizer for stimulating the plant growth were identified. The higher adsorption capacity of PO 4 3- and NO 3 - ions by LDH MgAl @CWGB (PO 4 3-  = 6.98 mgP/g, NO 3 -  = 2.82 mgN/g) compared with pristine coffee ground waste biochars (CWGB; PO 4 3-  = 0.19 mgP/g, NO 3 -  = 0.32 mgN/g) was mainly due to the incorporation of Mg/Al mixed oxides and Cl contents. Chemisorption and intra-particle mainly controlled the adsorptive recovery of PO 4 3- and NO 3 - ions by CWGB and LDH MgAl @CWGB in aqueous phases and their adsorption toward CWGB and LDH MgAl @CWGB proceeded endothermically and spontaneously. The changes in the major adsorption mechanisms of PO 4 3- and NO 3 - ions from ligand exchange (CWGB) to electrostatic surface complexation and anion-exchange (LDH MgAl @CWGB) supported the conclusion that the alternation of the surface features through Mg/Al LDH functionalization might improve selectivity and adsorption capacity of PO 4 3- and NO 3 - ions onto CWGB under the co-existence of Cl - , SO 4 2- , and HCO 3 - ions. Since PO 4 3- - and NO 3 - -loaded LDH MgAl @CWGB exhibited much higher seed germination, root and shoot growth rates of garden cress seeds (Lepidium sativum L) than other liquid and solid matrices, including 5 mgP/L PO 4 3- and 5 mgN/L NO 3 - , 10 mgP/L PO 4 3- and 10 mgN/L NO 3 - , and LDH MgAl @CWGB, it can be postulated that PO 4 3- - and NO 3 - -loaded LDH MgAl @CWGB could be practically applicable to the agricultural field as a slow-release fertilizer to facilitate the seed germination, root and shoot growth of the plants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

The organic fouling characteristics of hollow fiber ultrafiltration (HFUF) and multibore ultrafiltration (MBUF) membranes from long-term ultrafiltration (UF) membrane systems were systemically investigated in this study. The objective was to obtain insights into the fouling behavior of dissolved organic matter (DOM) in a pilot-scale ultra-high-recovery membrane filtration system (p-UHMS) used for surface water treatment. The pilot system consisted of a series of two different UF membranes (1st stage: polyvinylidene fluoride (PVDF) HFUF and 2nd stage: polyethersulfone (PES) MBUF). It was designed to feed the HFUF concentrate to the MBUF membranes to achieve ≥99.5 % total water recovery for surface water treatment, as these advances might enhance the production efficiencies of drinking water. The experimental results confirmed that hydrophobic DOM controlled the formation of HFUF membrane organic fouling, whereas hydrophilic DOM, including polysaccharide-like and protein-like matter, promoted MBUF membrane fouling. These opposing trends were attributed to the hydrophilic characteristics of the MBUF membrane surfaces (contact angle: PVDF = 90-130° and PES ≤ 80°), which reduced the hydrophobic interactions between the UF membrane surfaces and foulants. The performance declines of the MBUF membrane due to fouling layer formation was considerably severer than those of the HFUF membrane, decreasing total permeate water in the p-UHMS. Moreover, the quantity of the desorbed MBUF membrane foulants via 0.1 N NaOH was roughly 7.2 times larger than that of the desorbed HFUF membrane foulants through 0.1 N NaOH, indicating that alkaline-based cleaning agent could much more efficiently recover the performance of the fouled MBUF membranes. Hence, adequate cleaning strategies using alkaline-based agent for the MBUF membrane appeared to be essential for preventing the performance deterioration of the p-UHMS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

In this study, NaOH-assisted H 2 O 2 post-modification was proposed as a novel strategy to enhance the adsorption of radioactive strontium (Sr) onto residual coffee waste biochars (RCWBs). To validate its viability, the adsorption capacities and mechanisms of Sr(II) using pristine (RCWB P ), H 2 O 2 post-modified (RCWB HP ), and NaOH-assisted H 2 O 2 post-modified residual coffee waste biochars (RCWB NHP ) were experimentally and theoretically investigated. The highest adsorption capacity of Sr(II) for RCWB NHP (10.91 mg/g) compared to RCWB HP (5.57 mg/g) and RCWB P (5.07 mg/g) was primarily attributed to higher negative surface zeta potential (RCWB NHP = -5.66 → -30.97 mV; RCWB HP = -0.31 → -11.29 mV; RCWB P = 1.90 → -10.40 mV) and decoration of Na on the surfaces of RCWB P via NaOH-assisted H 2 O 2 post-modification. These findings agree entirely with the theoretical observations that the adsorption of Sr(II) onto RCWB P and RCWB HP was controlled by electrostatic interactions involving carbonyls whereas enriched carboxylic acids and decorated Na on the surfaces of RCWB NHP through the replacement of Mg and K by NaOH-assisted H 2 O 2 modification stimulated electrostatic interactions and cation exchanges governing the adsorption of Sr(II). Hence, NaOH-assisted H 2 O 2 post-modification seemed to be practically applicable for improving the adsorption capacity of Sr(II) using RCWB-based carbonaceous adsorbents in real water matrices., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The single adsorption of radioactive barium (Ba(II)), cobalt (Co(II)), and strontium (Sr(II)) ions using pristine (SCWB-P) and chemically activated spent coffee waste biochars with NaOH (SCWB-A) were thoroughly explored in order to provide deeper insights into the changes in their adsorption mechanisms through alkaline chemical activation. The greater removal efficiencies of SCWB-A (76.6-97.3%) than SCWB-P (45.6-75.2%) and the consistency between the adsorptive removal patterns (Ba(II) > Sr(II) > Co(II)) and oxygen bond dissociation enthalpies (BaO (562 kJ/mol) > SrO (426 kJ/mol) > CoO (397 kJ/mol)) of radioactive species supported the assumption that the adsorption removal of radioactive species with spent coffee waste biochars highly depended on the abundances of O-containing functional groups. The calculated R 2 values of the pseudo-first-order (SCWB-P = 0.998-0.999; SCWB-A = 0.850-0.921) and pseudo-second-order kinetic models (SCWB-P = 0.988-0.998; SCWB-A = 0.935-0.966) are evident that the physisorption mainly controlled the adsorption of radioactive species toward SCWB-P and the chemisorption played a crucial role in their adsorptive removal with SCWB-A. From the calculated intra-particle diffusion, isotherm, thermodynamic parameters, it can be concluded that the intra-particle diffusion and monolayer adsorption primarily governed the adsorption of radioactive species using SCWB-P and SCWB-A, and their adsorption processes occurred spontaneously and endothermically. The dominant adsorption mechanism of spent coffee waste biochars was changed from physisorption (ΔH° of SCWB-P = 21.6-29.8 kJ/mol) to chemisorption (ΔH° of SCWB-A = 42.4-81.3 kJ/mol) through alkaline chemical activation. The distinctive M-OH peak in the O1s XPS spectra of SCWB-A directly corresponding to the decrease in the abundances of O-containing functional groups confirms again that the enrichment of O-containing functional groups markedly facilitated the adsorption removal of radioactive species by chemisorption occurred at the inner and outer surfaces of spent coffee waste biochars., (Copyright © 2021 Elsevier Inc. All rights reserved.)

This study investigated the single and competitive adsorption characteristics of micropollutants using the pristine and alkali-modified spent coffee grounds (SCG) biochars. The alkali modification substantially improved the physicochemical characteristics of the SCG biochars (specific surface area and pore volume), which may have led to differences in the adsorption behaviors of the micropollutants. The pseudo second order model (R 2 ≥ 0.990) better described the single and competitive adsorption kinetics than the pseudo first order model (R 2 ≥ 0.664). It is evident that chemisorption played a key role in the removal of the micropollutants by the pristine and alkali-modified SCG biochars. The single and competitive adsorptions of the micropollutants were highly dependent on the solution pH and ionic strength since the pore-filling effects, electrostatic and hydrophobic interactions governed their removal by the pristine and alkali-modified SCG biochars. The higher removal efficiencies of the micropollutants by the alkali-modified SCG biochars (≥ 44.5%) in the presence of dissolved organic matter compared to the pristine SCG biochars (≤ 18.5%) support the assumption that alkali modification could markedly reinforce the surface structural properties of the SCG biochars related to the adsorption capacities., (Copyright © 2020 Elsevier B.V. All rights reserved.)